**The Study of Inflow Improvement in Spark Engines by Using New Concepts of Air Filters**

Sorin Raţiu and Corneliu Birtok-Băneasă

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48137

## **1. Introduction**

186 Internal Combustion Engines

Sweden.

[27] Per Andersson, Lars Eriksson and Lars Nielsen "Modeling and Architecture Examples of Model Based Engine Control" Vehicular Systems, ISY, Linköping University,

[28] Yaojung Shiao, John J. Moskwa, "Model-Based Cylinder-By-Cylinder Air-Fuel Ratio Control for SI Engines using Sliding Observers" Proceedings of the 1996 IEEE International Conference on Control Application Dearborn, MI. September 15-18, 1996.

> The piston internal combustion engine is a thermal engine that converts the chemical energy of the engine fluid fuel into mechanical energy. Engine fluid developments are achieved by means of a piston. The alternative movement of the piston inside a cylinder becomes rotating movement due to the crank gear.

> For an internal combustion engine, the gas changing process encloses the intake and exhaust, which condition each other. The intake process is the process during which fresh fluid (air) enters the engine cylinders. The intake (or filling) determines the amount of fresh fluid retained in the cylinder after closing the last filling body and thus the mechanical energy developed during relaxation. The exhaust determines the purification degree of the cylinder with a view to a subsequent fill. In other words, the bigger the amount of fresh fluid (respectively air) retained into the engine cylinders, the higher the engine performance. The large amount of air in the engine cylinders means high pressure and low temperature on the inlet. This is the origin of the idea for this study which seeks ways to maximize, as much as possible, the amount of air introduced into the engine cylinders (by increasing pressure and decreasing temperature into cylinders), during an operating cycle, the costs for this goal being minimal.

Cylinder filling can be normal or forced (supercharging).

Normal filling, or normal inlet, typical of only 4-stroke engines, is achieved due to the piston's movement in the cylinder, in the sense of volume increase. Volume growth is recorded in the intake stroke, the fresh fluid with atmospheric pressure on the inlet.

Forced filling is achieved when the inlet pressure is greater than atmospheric pressure, indispensable in the 2-stroke engine without gas exchange bound drives. Forced filling can be achieved by supercharging when special equipment prepares the fresh fluid to enter the engine inlet at a pressure greater than the atmospheric one.

© 2012 Raţiu and Birtok-Băneasă, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Raţiu and Birtok-Băneasă, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The cylinder filling process is strongly influenced by gas-dynamic losses on the engine intake route. There are two kinds of losses:


$$
\Delta p = \xi \cdot \rho \cdot \frac{w^2}{2} \tag{1}
$$

where is the pressure loss coefficient, w is the flow speed of the fresh fluid and is its density.

Due to these losses, the amount of fresh charge retained in the engine cylinders, while providing information on the filling conditions, cannot serve as a comparison standard for different engines, but only for the same engine (the size of the losses mentioned above differs from one engine to another). This is why we introduce the notion of filling degree, or filling coefficient, or filling efficiency as a criterion for assessing filling perfection [1]:

$$
\eta\_v = \frac{\mathcal{C}}{\mathcal{C}\_0} \tag{2}
$$

where C is the amount of fresh fluid actually retained in the cylinder, and C0 is the amount of fresh fluid that could be retained in the cylinder, under the state conditions of the engine inlet, i.e. without taking into account the losses mentioned above.

Proper filtering of the air that enters the internal combustion engine cylinder is essential to extend its operation. Preventing the intake of various impurities along with atmosphere air significantly reduces the wear and tear of engine parts in relative movement.

Unfortunately, besides the function of filtering air drawn from the atmosphere, the air filter – as a distinct part in engine composition - is a significant gas-dynamic resistance interposed on the suction route. If it is not cleaned regularly and the vehicle is driven frequently in dusty areas, the suction pressure pa is reduced consistently and the filling efficiency <sup>v</sup> suffers penalties [1].

The air filters for filtrating sucked air, needed for the running of internal combustion engines, are made in several variants that differ according to the filtration principle:


These variants have the following disadvantages:

 the existence of the filter element inside the case marks increased gas-dynamic resistance on the absorbed air (resulting in insufficient absorption phenomenon);


Air filtration is characterized by the following parameters:

188 Internal Combustion Engines

formula [1]:

suffers penalties [1].



These variants have the following disadvantages:

density.

intake route. There are two kinds of losses:

and hence the filling penalty.

The cylinder filling process is strongly influenced by gas-dynamic losses on the engine



> *<sup>w</sup> <sup>p</sup>*

where is the pressure loss coefficient, w is the flow speed of the fresh fluid and is its

Due to these losses, the amount of fresh charge retained in the engine cylinders, while providing information on the filling conditions, cannot serve as a comparison standard for different engines, but only for the same engine (the size of the losses mentioned above differs from one engine to another). This is why we introduce the notion of filling degree, or

0

where C is the amount of fresh fluid actually retained in the cylinder, and C0 is the amount of fresh fluid that could be retained in the cylinder, under the state conditions of the engine

Proper filtering of the air that enters the internal combustion engine cylinder is essential to extend its operation. Preventing the intake of various impurities along with atmosphere air

Unfortunately, besides the function of filtering air drawn from the atmosphere, the air filter – as a distinct part in engine composition - is a significant gas-dynamic resistance interposed on the suction route. If it is not cleaned regularly and the vehicle is driven frequently in dusty areas, the suction pressure pa is reduced consistently and the filling efficiency <sup>v</sup>

The air filters for filtrating sucked air, needed for the running of internal combustion

 the existence of the filter element inside the case marks increased gas-dynamic resistance on the absorbed air (resulting in insufficient absorption phenomenon);

engines, are made in several variants that differ according to the filtration principle:

*C C*

filling coefficient, or filling efficiency as a criterion for assessing filling perfection [1]:

*v*

inlet, i.e. without taking into account the losses mentioned above.

significantly reduces the wear and tear of engine parts in relative movement.

2 2

(1)

(2)


Composition of dust particles in the air, for example see [2]:

Airborne dust is extremely variable both as component material and particle size, depending on geographical area and climate. In general, airborne dust contains SiO2, CaO2, MgO, Fe2O3, Al2O3, alkaline material, organic material, soot, debris and smoke. Most dangerous for the engine are quartz particles (sand), quartz being one of the strongest abrasives. Organic substances are harmless to the engine.

The density of dust in the air is between 0.0002 g/m3 in winter and 3-4 g/m3 in summer, on earth roads from 0.5 to 1 m height above the ground. On paved roads, in summer, dust content in the air is 0.001 to 0.002 g/m3, i.e. 20 to 30 times higher than in winter; the density variation between the minimum and maximum, i.e. from 0.0002 to 4 g/m3, is 1 to 20 000. If during daytime you can see only up to 25 to 30 m, there is about 1g dust/m3 of air.

The most dangerous particles are quartz grains exceeding 0,010 mm, quartz being a powerful abrasive which causes wear and tear 2-3 times more than smaller particles. There is no air filter to stop all the dust in the air, meaning one with 100% filtration efficiency.

## **2. Brief history of the evolution of air filters**

At the beginning of the internal combustion engine evolution, the air filter's role was limited to the simple function of filtering the air entering the cylinders, air absorption taking place only from the engine compartment, regardless of season. Filter element was made of stainless steel sieves overlaid in 5 to 10 layers. Filter shape, respectively of the filter element, was mostly cylindrical (Figures 1-4) [2].

**Figure 1.** FORD T Model 1928

**Figure 2.** FORD A Model 1929

**Figure 3.** FORD V8 1932

#### **Figure 4.** FORD V8 1932

In certain racing engines with carburetors mounted on each cylinder, there is even no air filter, the engine sucking air directly from the engine compartment, without pre-filtering it (Figure 5).

**Figure 5.** MILLER V16 1931

The filter element becomes a consumable item, being replaced at road running intervals set by each manufacturer.

After the '40s, differential absorption of air depending on season starts to appear: in summer outside the engine compartment and in winter from the exhaust manifold area (Figures 6- 11) [2].

The filter element known today as microporous or textile cardboard appears much later, in a variety of forms, the most common being the panel (Figure 12).

**Figure 6.** . FORD MUSTANG I 1964

190 Internal Combustion Engines

**Figure 2.** FORD A Model 1929

**Figure 3.** FORD V8 1932

**Figure 4.** FORD V8 1932

**Figure 5.** MILLER V16 1931

(Figure 5).

In certain racing engines with carburetors mounted on each cylinder, there is even no air filter, the engine sucking air directly from the engine compartment, without pre-filtering it

**Figure 7.** FORD MUSTANG II 1974

**Figure 8.** FORD MUSTANG GT 1982

**Figure 9.** FORD MUSTANG 1994

**Figure 10.** FORD MUSTANG 2001

**Figure 11.** FORD MUSTANG 2005

**Figure 12.** Panel type air filter

## **3. Super absorbing air filters (SAAF) – Own concepts [2,5]**

From the outset it should be noted that the concepts proposed by the authors refer exclusively to air filter casing. The filter element is standard, purchased from well-known manufacturers.

The super absorbing or multifunction filters designed by the authors fulfil, besides the main task of filtering the air, the following functions:

To capture the air;

192 Internal Combustion Engines

**Figure 9.** FORD MUSTANG 1994

**Figure 10.** FORD MUSTANG 2001

**Figure 11.** FORD MUSTANG 2005

**Figure 12.** Panel type air filter


Here follows a classification of the super absorbing filters depending on assembly position, gauge dimensions and air intake function.

## **3.1. Super absorbing cylindrical air filter with internal diffuser (SAAFid)**

The internal diffuser has the additional function of accelerating air speed out of the filter. The design geometry provides considerable increase in the coefficient of filling the cylinders with air.

The internal diffuser has variable sizes, depending on engine displacement. The larger the displacement is, the higher the diffuser sizes are, and vice versa.

**Figure 13.** Super absorbing filter with internal diffuser: a, b – physical models

## **3.2. Supliform super absorbing air filter (suSAAF)**

It is mainly based on space-saving, reduced gauge dimensions (flexibility), being useful where the engine compartment is very tight (large capacity engines with supercharging installations). This filter allows, in its turn, function multiplication, namely, besides the main function of filtering the air, the filter increases the absorption and intake rate, as well as the speed of the absorbed air, also cooling it. This filter type can be a filter with one filter area and external collector, and a filter with dual filtration area.

The supliform air filter with one filter area consists of an axial external collector of cylindrical-concave shape (in radial section it is an arc), lined with filter element, concentration surfaces and connection cylinder (figure14).

The arc-shaped axial external sensor is radially closed at both ends with two concentration surfaces (crescent shaped) (Figures 14.c).

The filter element is recessed axially between the collector edges and radially between the concentration surfaces.

a – sketch, b – virtual model made in AutoDesk Inventor, c – exploded virtual model, d – physical model **Figure 14.** Supliform super absorbing air filter with one filter area and external collector

On one of the concentration surfaces there is the fitting cylinder (Figure 14.d), which provides connection of the supliform filter to the engine inlet.

The collector, together with the concentration surfaces, captures radially and directs axially the air into the fitting cylinder (towards filter exit).

Due to its geometric shape, the collector ensures the minimum gas-dynamic resistance and creates a slight boost which increases proportionally with the speed of the vehicle, increasing considerably the amount of air absorbed and thus the filling coefficient of the engine.

194 Internal Combustion Engines

concentration surfaces.

function of filtering the air, the filter increases the absorption and intake rate, as well as the speed of the absorbed air, also cooling it. This filter type can be a filter with one filter area

The supliform air filter with one filter area consists of an axial external collector of cylindrical-concave shape (in radial section it is an arc), lined with filter element,

The arc-shaped axial external sensor is radially closed at both ends with two concentration

The filter element is recessed axially between the collector edges and radially between the

(a) (b)

(c) (d)

a – sketch, b – virtual model made in AutoDesk Inventor, c – exploded virtual model, d – physical model **Figure 14.** Supliform super absorbing air filter with one filter area and external collector

and external collector, and a filter with dual filtration area.

concentration surfaces and connection cylinder (figure14).

surfaces (crescent shaped) (Figures 14.c).

(a) (b)

(c)

a – sketch, b – virtual model made in AutoDesk Inventor, c – physical model

**Figure 15.** Supliform super absorbing air filter with dual filtration area

The filter element has a concave semi-cylindrical shape (Figure 14.d) and defines the area located between the collector edges and concentration surfaces. It is made of micron cardboard placed so that it forms the lateral area of the filter element (in radial section the micron cardboard has a VV shape). The cardboard provides a fine filter (microns) and is covered on the outside with a millimeter sieve, which allows coarse air filtering (millimeter). The micrometer cardboard and millimeter sieve are rigid (fixed) at both open ends with silicone semi-rings for better alignment and ideal tightness relative to the sensor edges and concentration surfaces.

The supliform air filter is mounted radially to the geometric axis of the vehicle (perpendicular on travel direction) for proper intake and absorption performance (Figure 16).

**Figure 16.** Mounting supliform air filter on engine

## **3.3. Super absorbing air filter with wide filtration range (SAAFwr)**

This type of filter is made up of a front diffuser and a side surface with guiding cells, allowing the capture of both front and side air, thus increasing the surface of air penetration into the filter.

**Figure 17.** Super absorbing air filter with wide filtration range

## **4. Dynamic air transfer device (DATD) [2,5]**

During operation of internal combustion engines fitted on motor vehicles in summer, there can be noted two shortcomings of the super absorbing filters, leading to their poor performance:


Figure 18 presents the most disadvantageous fitting solutions in terms of exposure to thermal radiation and eddy currents.

**Figure 18.** Assemblies that lead to direct exposure of the filters

196 Internal Combustion Engines

concentration surfaces.

into the filter.

performance:

**Figure 16.** Mounting supliform air filter on engine

**Figure 17.** Super absorbing air filter with wide filtration range

**4. Dynamic air transfer device (DATD) [2,5]** 

covered on the outside with a millimeter sieve, which allows coarse air filtering (millimeter). The micrometer cardboard and millimeter sieve are rigid (fixed) at both open ends with silicone semi-rings for better alignment and ideal tightness relative to the sensor edges and

The supliform air filter is mounted radially to the geometric axis of the vehicle (perpendicular

on travel direction) for proper intake and absorption performance (Figure 16).

**3.3. Super absorbing air filter with wide filtration range (SAAFwr)** 

This type of filter is made up of a front diffuser and a side surface with guiding cells, allowing the capture of both front and side air, thus increasing the surface of air penetration

During operation of internal combustion engines fitted on motor vehicles in summer, there can be noted two shortcomings of the super absorbing filters, leading to their poor It was tried to use a separator compartment for the air filter (Figure 19). But the separator compartment does not provide ideal insulation against the engine compartment, allowing thermal radiation to enter the air filter. Due to its design, turbulent air currents are created inside the separator compartment.

**Figure 19.** Installing filters in separator compartments

Moreover, the extension of the intake route outside the engine compartment is also practised. The example is given by mounting the air filter in the front bumper of a Honda Civic R Type. At the same time, the incorporation of the air filter in aluminum or carbon cage is also practised.

By using the above solutions, the disadvantages mentioned are partially eliminated, but there is significant pressure loss due to extension of the intake route and existence of casting. Suction pressure is reduced consistently. On average, the intake route distances increase by over 500 mm, leading to increased drag created by additional friction arising from contact with the intake route wall.

Considering the above drawbacks, an efficient intake device was designed for internal combustion engines, called *dynamic air transfer device* (DATD) (Figure 20). It helps improve air circulation to the filter air through the engine compartment.

a - design scheme: 1 - external collector diffuser, 2 - pipe connection, 3 - axial external collector, A, B - connecting surfaces; b - real overview; c - axial external collector and external collector diffuser - overview; d - different types of axial external collector and external collector diffuser.

**Figure 20.** Dynamic air transfer device (DATD)

The novelty consists in mounting external collector diffusers longitudinally with the vehicle axis, in the front area (in front of the radiator area or in the front bumper). They drive the air trapped outside the engine compartment, through the pipe connection, to the axial external collector, where the transfer to the air filter takes place.

The dynamic air transfer device consists of:

**Figure 21.** External collector diffusers - physical models


#### **Figure 22.** Pipe connection

198 Internal Combustion Engines

cage is also practised.

with the intake route wall.

Civic R Type. At the same time, the incorporation of the air filter in aluminum or carbon

By using the above solutions, the disadvantages mentioned are partially eliminated, but there is significant pressure loss due to extension of the intake route and existence of casting. Suction pressure is reduced consistently. On average, the intake route distances increase by over 500 mm, leading to increased drag created by additional friction arising from contact

Considering the above drawbacks, an efficient intake device was designed for internal combustion engines, called *dynamic air transfer device* (DATD) (Figure 20). It helps improve

air circulation to the filter air through the engine compartment.

a - design scheme: 1 - external collector diffuser, 2 - pipe connection, 3 - axial external collector,

d - different types of axial external collector and external collector diffuser.

collector, where the transfer to the air filter takes place.

**Figure 20.** Dynamic air transfer device (DATD)

The dynamic air transfer device consists of:

**Figure 21.** External collector diffusers - physical models

A, B - connecting surfaces; b - real overview; c - axial external collector and external collector diffuser - overview;

(a) (b)

(a) (b) (c) (d)

The novelty consists in mounting external collector diffusers longitudinally with the vehicle axis, in the front area (in front of the radiator area or in the front bumper). They drive the air trapped outside the engine compartment, through the pipe connection, to the axial external 3. The axial external collector (mono or bi-route), Figure 23, is mounted on the super absorbing air filter oriented to the high heat radiation areas (exhaust manifold, radiator, engine). It takes at least 30% of the lateral filter area, being at a well-determined distance away from the filter (between 3 and 8 mm). Its role is to transfer the air flow in the filter, flow divided into two components: one that actually enters the filter, the actual flow being admitted into the engine cylinders and one that surrounds the lateral surface of the filter, leading to keeping a relatively low filter temperature.

While driving the vehicle, the air is taken over by the external collector diffusers which enhance its speed, concentrate and convey it through the pipe connection to the axial external collector that transfers it to the super absorbing air filter.

The air stream transferred (brought) from outside the engine compartment has laminar focused flow. Speed increases (task performed by the external collector diffusers), and at the same time the air flow temperature decreases significantly. Because of its design geometry, the axial external sensor ensures good transfer and dispersion of the air on the side area of the super absorbing air filter. The amount of transfered air increases proportionally with the speed of the vehicle.

**Figure 24.** a - DATD mounted on the engine; b - component parts: 1 - external collector diffusers, 2 pipe connection, 3 - bi-route axial external collector

Advantages of DATD:


Depending on engine capacity, one should use one or two external collector diffusers and an axial external collector in one or two transfer routes with varying sizes.

## **4.1. Experimented DATD**

**Figure 25.** DATD mounted on Renault LAGUNA 1.6 16V

Differential pressure measurements were made both in the presence of the axial external collector of the DATD, and in its absence, in the suction area of the air filter, on different speed ranges. Data were taken while driving in real traffic at different speeds of the vehicle.

The Study of Inflow Improvement in Spark Engines by Using New Concepts of Air Filters 201

**Figure 26.** DATD mounted WV Golf 5, 1.4 16v

200 Internal Combustion Engines

Advantages of DATD:

pipe connection, 3 - bi-route axial external collector

 the combustion process is improved; the tendency is toward dynamic inlet;

**4.1. Experimented DATD** 

vehicle.

the air transfer to the filter has laminar focused flow;

**Figure 25.** DATD mounted on Renault LAGUNA 1.6 16V

the low air temperature provides improved filling efficiency;

**Figure 24.** a - DATD mounted on the engine; b - component parts: 1 - external collector diffusers, 2 -

(a) (b)

a slight boost is created increasing proportionally with the speed of the vehicle;

it allows shortening the distance between the filter and the intake manifold.

axial external collector in one or two transfer routes with varying sizes.

Depending on engine capacity, one should use one or two external collector diffusers and an

Differential pressure measurements were made both in the presence of the axial external collector of the DATD, and in its absence, in the suction area of the air filter, on different speed ranges. Data were taken while driving in real traffic at different speeds of the

**Figure 27.** DATD, bi-route mounted on Honda Civic, 1.6

**Figure 28.** DATD, mounted on Renault Megane Coupe

For measurements in the transfer area of the axial external collector - air filter, the pressure intake port was oriented axially to the airflow direction.

For measurements without DATD, in the suction area of the air filter, the pressure intake port is directed axially to the air absorption direction.

One can notice a higher air capture and transfer effect obtained by DATD, in comparison with the simple absorption of the super absorbing air filter. This effect is accentuated by higher values of the relative air pressure in the capture area obtained by DATD, in comparison with the relative pressure values in the absorption area of the air filter in the absence of DATD. This is particularly beneficial, especially for non-supercharged engine intake (normal inlet), the amount of air admitted into the engine cylinders being directly proportional to the intake pressure.

**Figure 29.** Comparative graph of the relative air pressure fields in the suction area of the air filter, in the presence and respectively absence of DATD

Here are some comparative measurements of the temperatures of the outer surfaces of the original classic air filter (OAF) and super absorbing air filters with DATD (SAAF+DATD) in real traffic conditions.

From the graphs above it can be seen that the temperatures of the outer surfaces of the super absorbing filters, in combination with the dynamic air transfer device (SAAF+DATD), are much lower than the ones corresponding to the outer surfaces of the original air filters (OAF). Consequently, the use of super absorbing air filters together with DATD leads to less acute air heating on the intake route and therefore improvement of the filling coefficient.

**Figure 30.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Opela Astra 1.4i

proportional to the intake pressure.

the presence and respectively absence of DATD

**presure [Pa]**

real traffic conditions.

filling coefficient.

higher values of the relative air pressure in the capture area obtained by DATD, in comparison with the relative pressure values in the absorption area of the air filter in the absence of DATD. This is particularly beneficial, especially for non-supercharged engine intake (normal inlet), the amount of air admitted into the engine cylinders being directly

> w ith DATD w ithout DATD

**Figure 29.** Comparative graph of the relative air pressure fields in the suction area of the air filter, in

25 30 35 40 45 50 55 60 65 **vehicle speed [km/h]**

Here are some comparative measurements of the temperatures of the outer surfaces of the original classic air filter (OAF) and super absorbing air filters with DATD (SAAF+DATD) in

From the graphs above it can be seen that the temperatures of the outer surfaces of the super absorbing filters, in combination with the dynamic air transfer device (SAAF+DATD), are much lower than the ones corresponding to the outer surfaces of the original air filters (OAF). Consequently, the use of super absorbing air filters together with DATD leads to less acute air heating on the intake route and therefore improvement of the

> OAF SAAF+DATD

**Figure 30.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Opela Astra 1.4i

Opel Astra 1.4 l

Temperature [ 0C]

**Figure 31.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Opela Astra 2.0tdi

**Figure 32.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Suzuki Samurai

**Figure 33.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Dacia 1.3

**Figure 34.** Temperatures of the outer surfaces of the OAF and SAAF+DATD for Dacia Logan 1.4i

## **5. Integrated deflector (ID) for attenuation of thermal radiation coming from the cooling radiator [2]**

The thermal radiation and warm air from the engine cooling radiator extra heat the air filter and intake manifold. The absorbed air is also heated thus decreasing its density, the engine performance diminishing especially in hot weather. The air filter and intake manifold temperatures vary, in this case, between 60 and 85 oC, depending on the car speed.

**Figure 35.** Illustration of thermal radiation orientation towards the air filter

**Figure 36.** Filter assembly without the cooling radiator's integrated deflector

The cooling radiator's integrated deflector is designed to reduce these shortcomings, being mounted behind the radiator fan to direct the air flow beneath the inlet level (downwards). The deflector is thermally insulated (Figure 38), the filter and manifold temperatures falling within the range 25 ... 37 oC when the deflector is used.

**Figure 38.** Integrated deflector - physical model

**from the cooling radiator [2]** 

**5. Integrated deflector (ID) for attenuation of thermal radiation coming** 

The thermal radiation and warm air from the engine cooling radiator extra heat the air filter and intake manifold. The absorbed air is also heated thus decreasing its density, the engine performance diminishing especially in hot weather. The air filter and intake manifold

temperatures vary, in this case, between 60 and 85 oC, depending on the car speed.

**Figure 35.** Illustration of thermal radiation orientation towards the air filter

**Figure 36.** Filter assembly without the cooling radiator's integrated deflector

within the range 25 ... 37 oC when the deflector is used.

**Figure 37.** Radiator fan

The cooling radiator's integrated deflector is designed to reduce these shortcomings, being mounted behind the radiator fan to direct the air flow beneath the inlet level (downwards). The deflector is thermally insulated (Figure 38), the filter and manifold temperatures falling

**Figure 39.** a,b - Overview of radiator with mounted deflector

As already mentioned, the purpose of the integrated deflector is to direct downward the hot airflow passing through the engine cooling radiator (Fig. 40, b).

**Figure 40.** Integrated deflector: a - sketch, b - operation principle

The technical problem solved consists in protecting the intake manifold and air filter from the heat radiation coming from the engine cooling radiator.

By use of the deflector integrated the following advantages are obtained:

 downward direction of the hot airflow coming from the cooling radiator (thermal radiation), outside the engine compartment;

 maintaining an optimum temperature of the intake manifold and air filter (to avoid overheating them).

The integrated deflector is provided with a deflector wall (Figure 41), which has a rectangular concentration area (2) fixed on the upper end. The concentration trapezoidal surfaces (3) and (4) are fixed on the lateral ends of the deflector wall (1), with the large trapeze end at the bottom. The deflector wall (1) has two or more directional windows (5).

**Figure 41.** Integrated deflector - virtual model, made in Autodesk Inventor: 1 - deflector wall, 2 - rectangular concentration area; 3, 4 - trapezoidal concentration surfaces; 5 - directional windows

The bottom surface between bases (3), (4) and the bottom edge of the deflector wall (1) is open (free) to allow the evacuation of most hot airflow coming from the cooling radiator. The directional windows (5) allow additional exhaust of the hot airflow coming from the cooling radiator.

The deflector is not bad for engine cooling, the operating temperature of the coolant remaining within normal operating parameters.

Further experimental measurements are shown for comparative temperatures of intake air in the presence and absence of the deflector. Please note that in summer tests were made on

**Figure 42.** Overview of engine radiator tested: a - without integrated deflector, b - with integrated deflector mounted

4 different cars, drawing the conclusion that the deflector has no adverse effect on engine cooling, the operating temperature of the coolant remaining within the parameters specified by the manufacturer.

**Figure 43.** Intake air temperature values in the proximity of the air filter

As illustrated in Figure 45, the intake air temperature values for the original air filter (OAF) and the super absorbing air filter (SAAF) are similar in size and relatively high, leading to low density of the fresh load in the cylinders and thus to reducing the filling efficiency. Conversely, the temperature values recorded in the presence of the super absorbing air filter with integrated deflector (SAAF+ID) and to which the dynamic air transfer device is added (SAAF+DADT+ID) are much lower than the previous ones, which favors the improvement of the filling efficiency.

In conclusion, we can say that the dynamic air transfer device together with the integrated heat deflector, lead on the one hand to increasing the fresh fluid intake pressure, and on the other hand to lowering its temperature, both solutions contributing to increasing the filling efficiency v of the engine cylinders.

## **6. Experimental laboratory tests**

206 Internal Combustion Engines

cooling radiator.

deflector mounted

overheating them).

maintaining an optimum temperature of the intake manifold and air filter (to avoid

The integrated deflector is provided with a deflector wall (Figure 41), which has a rectangular concentration area (2) fixed on the upper end. The concentration trapezoidal surfaces (3) and (4) are fixed on the lateral ends of the deflector wall (1), with the large trapeze end at the bottom. The deflector wall (1) has two or more directional windows (5).

The bottom surface between bases (3), (4) and the bottom edge of the deflector wall (1) is open (free) to allow the evacuation of most hot airflow coming from the cooling radiator. The directional windows (5) allow additional exhaust of the hot airflow coming from the

(a) (b)

The deflector is not bad for engine cooling, the operating temperature of the coolant

Further experimental measurements are shown for comparative temperatures of intake air in the presence and absence of the deflector. Please note that in summer tests were made on

**Figure 42.** Overview of engine radiator tested: a - without integrated deflector, b - with integrated

(a) (b)

**Figure 41.** Integrated deflector - virtual model, made in Autodesk Inventor:

1 - deflector wall, 2 - rectangular concentration area;

remaining within normal operating parameters.

3, 4 - trapezoidal concentration surfaces; 5 - directional windows

The purpose of these experiments is to test the concepts of the super absorbing air filters and DATD designed and carried out by the authors, previously presented in detail. Testing was performed on an experimental stand, located in the Laboratory of Internal Combustion Engines of the Faculty of Engineering of Hunedoara, Romania.

The data were processed and compared with those obtained when operation took place the original engine filter provided by the manufacturer. There is clear improvement of pressure on the inlet route, when super absorbing filters and the dynamic air transfer device are installed.

The experimental measurements were based on a stand containing a 4-stroke 4-vertical inline cylinder spark ignition engine, the camshaft in the crankcase, Dacia brand, model 810.99, with carburettor, and related equipment, stand which allows setting the pressure field on the engine intake route (Figure 44), for example see [2,3].

**Figure 44.** Overview of experimental stand

**Figure 45.** a, b, c.; Position and number of pressure intake ports

A number of the pressure intake ports were made downstream the air filter and measurements were made at different operating regimes for the engine installed on the stand, for different super absorbing filters designed and made by the authors. The position of the pressure intake ports on the engine intake route is illustrated in Figure 45.

Measurements were performed in no-load (idling) engine motion at various revolutions. Relative pressure values were measured on the intake route points where pressure ports have been mounted, as shown in Figure 45. TESTO 510 digital manometer (0-100hPa) was used. For example see [3].

Also, to simulate vehicle movement, measurements were performed in the presence of a fan positioned in front of the cooling radiator of the engine installed on the stand.

Measuring the speed of airflow from the fan to the engine radiator took place using a digital anemometer, Lutron LM - 8010 type. Engine revolution was measured with a VELLEMAN DTO 6234N digital tachometer.

In addition, engine noise measurements were made for operation with different filter types, with a Lutron SL - 4012 type sound level meter.

Data were collected for the inlet system equipped with original classic air filter – OAF (Figure 46), super absorbing cylindrical air filter with internal diffuser – SAAFid (Figure 47), supliform super absorbing air filter – suSAAF (Figure 48), super absorbing filter with wide filtration range – SAAFwr (Figure 49) and for the dynamic air transfer device DATD (figure 50).

**Figure 46.** Original classic filter trial

208 Internal Combustion Engines

**Figure 44.** Overview of experimental stand

**Figure 45.** a, b, c.; Position and number of pressure intake ports

(b)

(a)

A number of the pressure intake ports were made downstream the air filter and measurements were made at different operating regimes for the engine installed on the stand, for different super absorbing filters designed and made by the authors. The position

(c)

Measurements were performed in no-load (idling) engine motion at various revolutions. Relative pressure values were measured on the intake route points where pressure ports

of the pressure intake ports on the engine intake route is illustrated in Figure 45.

810.99, with carburettor, and related equipment, stand which allows setting the pressure

field on the engine intake route (Figure 44), for example see [2,3].

**Figure 47.** Super absorbing cylindrical filter with internal diffuser trial

**Figure 48.** Supliform super absorbing filter trial

**Figure 49.** Super absorbing with wide filtration range trial

**Figure 50.** a, b, c: Dynamic air transfer device DATD trial

Further are presented comparative graphs of the relative pressure values recorded for each concept, for each individual pressure intake port.

Due to the presence of pressure waves generated by alternative movement of the pistons in the cylinders and the periodic opening and closing of the intake valves, pressure values fluctuate within a fairly wide range. Therefore, after stabilization of engine revolution, limit values (upper and lower) of the pressure in the ports mounted were registered and their average was calculated. These averages were used for plotting the graphs below.

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter

**Figure 51.** Values for pressure intake port 1, without vehicle movement simulation

The Study of Inflow Improvement in Spark Engines by Using New Concepts of Air Filters 211

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter

210 Internal Combustion Engines

**Figure 49.** Super absorbing with wide filtration range trial

**Figure 50.** a, b, c: Dynamic air transfer device DATD trial

concept, for each individual pressure intake port.


relative pressure [Pa]

Absorbing Air Filter

Further are presented comparative graphs of the relative pressure values recorded for each

(a) (b) (c)

Due to the presence of pressure waves generated by alternative movement of the pistons in the cylinders and the periodic opening and closing of the intake valves, pressure values fluctuate within a fairly wide range. Therefore, after stabilization of engine revolution, limit values (upper and lower) of the pressure in the ports mounted were registered and their

**Air fan velocity 0 m/s**

850 1350 1850 2350 2850 3350

average was calculated. These averages were used for plotting the graphs below.

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super

RPM

**Figure 51.** Values for pressure intake port 1, without vehicle movement simulation

OAF SAAFid suSAAF

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter

**Figure 53.** Values for pressure intake port 3, without vehicle movement simulation

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter

**Figure 54.** Values for pressure intake port 4, without vehicle movement simulation

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 56.** Values for pressure intake port 2, with vehicle movement simulation

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 57.** Values for pressure intake port 3, with vehicle movement simulation

The Study of Inflow Improvement in Spark Engines by Using New Concepts of Air Filters 213

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 58.** Values for pressure intake port 4, with vehicle movement simulation

212 Internal Combustion Engines

range

range

range

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

850 1350 1850 2350 2850 3350

RPM

**Air fan velocity 5 m/s**

**Air fan velocity 5 m/s**

OAF SAAFid suSAAF SAAFid+DATD SAAFwr

> OAF SAAFid suSAAF SAAfid+DATD SAAFwr

OAF SAAFid suSAAF SAAFid+DATD SAAFwr

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

**Air fan velocity 5 m/s**

850 1350 1850 2350 2850 3350

RPM

850 1350 1850 2350 2850 3350

RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

**Figure 55.** Values for pressure intake port 1, with vehicle movement simulation

relative pressure [Pa]

relative pressure [Pa]

relative pressure [Pa]

**Figure 56.** Values for pressure intake port 2, with vehicle movement simulation

**Figure 57.** Values for pressure intake port 3, with vehicle movement simulation

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 59.** Evolution of noise depending on engine revolution

The following are comparative graphs of the evolution of relative pressure on the intake route for each revolution regime, with vehicle movement simulation (air fan velocity 5 m/s).

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 60.** Evolution of relative pressure on intake route, 800 RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 61.** Evolution of relative pressure on intake route, 1500 RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 62.** Evolution of relative pressure on intake route, 2000 RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 63.** Evolution of relative pressure on intake route, 2500 RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 64.** Evolution of relative pressure on intake route, 3000 RPM

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration range

**Figure 65.** Evolution of relative pressure on intake route, 3500 RPM

## **7. Conclusions**

214 Internal Combustion Engines

range

range

range

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

<sup>1234</sup> pressure intake port

OAF SAAFid suSAAF SAAFid+DATD SAAFwr

OAF SAAFid suSAAF SAAFid+DATD SAAFwr

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

1234 pressure intake port

> OAF SAAFid suSAAF SAAFid+DATD SAAFwr

OAF – Original Air Filter, SAAFid – Super Absorbing Air Filter with internal diffuser, suSAAF – supliform Super Absorbing Air Filter, DATD – Dynamic Air Transfer Device, SAAFwr – Super Absorbing Air Filter with wide filtration

1234

pressure intake port

**Figure 61.** Evolution of relative pressure on intake route, 1500 RPM

relative pressure [Pa]

**Figure 62.** Evolution of relative pressure on intake route, 2000 RPM

relative pressure [Pa]

relative pressure [Pa]

**Figure 63.** Evolution of relative pressure on intake route, 2500 RPM

Studying the pressure evolution for each pressure intake port and at different engine revolutions (RPM), we can conclude the following [2,4]:


5. Following the evolution of pressure on the intake route for different engine revolutions it is found that the filters designed have much diminished pressure fluctuation as compared to the one induced by the original classic air filter (OAF) for low revolutions. At high revolutions, the evolution of pressure is somewhat similar for all filters.

Seen as a whole, we can say that the super absorbing air filters (SAAF) together with the dynamic air transfer device (DATD) and the integrated deflector (ID) for attenuation of thermal radiation coming from the cooling radiator, lead to the following advantages:


## **Author details**

Sorin Raţiu1,2,\* and Corneliu Birtok-Băneasă1,3,4 *1"Politehnica" University of Timisoara, Romania, 2Engineering Faculty of Hunedoara, Romania, 3Mechanical Faculty of Timisoara, Romania, 4Corneliu Group, Romania* 

## **8. References**


<sup>\*</sup> Corresponding Author

## **Understanding Fuel Consumption/Economy of Passenger Vehicles in the Real World**

Yuki Kudoh

216 Internal Combustion Engines

**Author details** 

*4Corneliu Group, Romania* 

Timişoara, pp. 15-90;

**8. References** 

1726-9679

Corresponding Author

 \*

[5] www.corneliugroup.ro

in the cylinders during an engine cycle;

Sorin Raţiu1,2,\* and Corneliu Birtok-Băneasă1,3,4 *1"Politehnica" University of Timisoara, Romania, 2Engineering Faculty of Hunedoara, Romania, 3Mechanical Faculty of Timisoara, Romania,* 

5. Following the evolution of pressure on the intake route for different engine revolutions it is found that the filters designed have much diminished pressure fluctuation as compared to the one induced by the original classic air filter (OAF) for low revolutions.

Seen as a whole, we can say that the super absorbing air filters (SAAF) together with the dynamic air transfer device (DATD) and the integrated deflector (ID) for attenuation of thermal radiation coming from the cooling radiator, lead to the following advantages:



[1] Raţiu S, Mihon L (2008) *Internal Combustion Engines for Motor Vehicles - Processes and* 

[2] Birtok-Băneasă C, Raţiu S (2011) *Air Intake of Internal Combustion Engines – Super Absorbing Filters - Dynamic Transfer Devices*, POLITEHNICA Publishing House,

[3] Raţiu S (2009) *Internal Combustion Engines for Motor Vehicles - Processes and Features –* 

[4] Raţiu S, Birtok-Băneasă C, Alic C, Mihon L (2009) *New concepts in modeling air filters for internal combustion engines*, 20th International DAAAM SYMPOSIUM "Intelligent Manufacturing & Automation: Theory, Practice & Education", Vienna, Austria, ISSN

*Laboratory Experiments*, MIRTON Publishing House, Timişoara, pp. 40-42;

*Features*, MIRTON Publishing House, Timişoara, pp. 44-47;

larger amount of air retained in the engine cylinders during an engine cycle.

At high revolutions, the evolution of pressure is somewhat similar for all filters.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/49944

## **1. Introduction**

The world is currently highly dependent upon oil for automotive transport. As a result, large amounts of greenhouse gas (GHG) emissions are generated in the passenger automotive sector and are having a substantial effect on the environment. Among the various measures from both the automotive technology side and the transport demand side to reduce energy consumption and GHG emissions, improving the fuel consumption (FC, expressed in litres of gasoline per hundred kilometres of travel [L/100 km]) or fuel economy (FE, usually expressed in [km/L] or miles per gallon [mpg]) of passenger vehicles is regarded as the most effective measure. In this regard, many regions and countries around the world have implemented FC/FE or GHG standards (An et al., 2011), and some — for example, the United States, the European Union, and Japan — are tightening their existing standards.

FC/FE and GHG standards are measured by using chassis dynamometer test cycles, which simulate a variety of driving conditions at typical highway and urban driving speeds in each country and region. However, it is quite well known that a gap exists between FC/FE values generated by dynamometer testing and real-world values worldwide (Schipper & Tax, 1994; Schipper, 2011). Real-world FC/FE values depend strongly upon each driver's style and location, upon the traffic congestion, weather, and corresponding use of accessories (especially air conditioning), and upon the vehicle's maintenance condition. No single test cycle can simulate all possible combinations of these factors. Although the energy roadmaps and CO2 reduction targets for the passenger automotive sector in each region and country are based mainly on FC/FE and GHG standards, it is the real-world values that matter. It is doubtful whether reduction targets can be met without more accurate realworld assessments of FC/FE and GHG emissions. Providing more accurate real-world FC/FE values will also better inform consumers of expected fuel costs.

© 2012 Kudoh, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Kudoh, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The many studies that have investigated FC/FE and GHG emissions in the real world have used several approaches. Schipper (2011) analysed FC trends for the entire passenger vehicle fleet in the United States, Australia, Japan, and several European countries by using national or regional statistics, as well as the impact of fuel prices upon FC/FE. Wang et al. (2008) explored the influence of driving patterns on FC in China by using a portable emissions measurement system and established an on-road FC estimation model. Duoba et al. (2005) tested the robustness of FE to changes in vehicle activity for hybrid vehicles (HVs) and their counterpart internal combustion engine vehicles by applying various driving schedules upon a chassis dynamometer in the U.S. Several studies have also analysed on-road FC/FE by using information collected by questionnaires or on the internet. Huo et al. (2011) examined the differences between standard test and real-world values for Chinese passenger vehicles by using data voluntarily reported by drivers on the internet; the study gathered 63,115 pieces of real-world FC data for 153 vehicle models. Sagawa & Sakaguchi (2000) analysed the FE of Japanese passenger vehicles using questionnaires, but they were unable to analyse the data with high statistical reliability because of sample number limitations (1,479 samples).

The use of internet-connected mobile phones has become widespread throughout the world, and the range of mobile phone contents and services provided includes those used to track the FC/FE of automobiles. In order to analyse real-world FC/FE in Japan with a high level of statistical reliability, the author's group put focus upon the FC/FE management service in which voluntarily reported FC log data of the vehicle users are collected through internet-connected mobile phones across Japan and developed and on-road (actual) FC database. The findings for the 24 months from October 2000 to September 2002 are reported by Kudoh et al. (2004).

Since 2000, the number of brand-new passenger vehicles sold in Japan has fluctuated between 4.26 and 4.76 million, which means that about 8% of the total passenger vehicle fleet was replaced with brand-new vehicles annually. Since the FC/FE of brand-new vehicles improved during this period, it is reasonable to conclude that the FC/FE performance of the passenger vehicle fleet itself should also have improved as these new vehicles replaced older ones. In addition, the mobile phone service provider whose log data were used to develop the actual FC database has reported an increase in the number of users in the 2000s.

The author's group therefore updated the database by extending the data collection period from 24 to 54 months and created a database consisting of 1,645,923 pieces of log data collected from October 2000 through March 2005, including information from 49,677 passenger vehicle users on 2,022 models sold in Japan and conducted a statistical analysis of actual FC for passenger HVs and other passenger vehicles with internal combustion engine in Japan (Kudoh et al., 2007; Kudoh et al., 2008). In addition to the previous achievements of the author's group, this paper addresses the effects of vehicle specifications towards the actual FC/FE of passenger vehicles in Japan, as derived from the database, from a statistical point of view.

## **2. Reasons for the FC/FE measurement gap**

In Japan, targets for FE standards are provided in the revised Law Concerning the Rational Use of Energy (known as the Energy-Saving Law) by implementing the "Top Runners Approach," which aims to establish energy-efficiency standards that meet or exceed the best energy-efficiency specifications for a product in an industry.

218 Internal Combustion Engines

The many studies that have investigated FC/FE and GHG emissions in the real world have used several approaches. Schipper (2011) analysed FC trends for the entire passenger vehicle fleet in the United States, Australia, Japan, and several European countries by using national or regional statistics, as well as the impact of fuel prices upon FC/FE. Wang et al. (2008) explored the influence of driving patterns on FC in China by using a portable emissions measurement system and established an on-road FC estimation model. Duoba et al. (2005) tested the robustness of FE to changes in vehicle activity for hybrid vehicles (HVs) and their counterpart internal combustion engine vehicles by applying various driving schedules upon a chassis dynamometer in the U.S. Several studies have also analysed on-road FC/FE by using information collected by questionnaires or on the internet. Huo et al. (2011) examined the differences between standard test and real-world values for Chinese passenger vehicles by using data voluntarily reported by drivers on the internet; the study gathered 63,115 pieces of real-world FC data for 153 vehicle models. Sagawa & Sakaguchi (2000) analysed the FE of Japanese passenger vehicles using questionnaires, but they were unable to analyse the data

with high statistical reliability because of sample number limitations (1,479 samples).

the 24 months from October 2000 to September 2002 are reported by Kudoh et al. (2004).

vehicles in Japan, as derived from the database, from a statistical point of view.

In Japan, targets for FE standards are provided in the revised Law Concerning the Rational Use of Energy (known as the Energy-Saving Law) by implementing the "Top Runners

**2. Reasons for the FC/FE measurement gap** 

The use of internet-connected mobile phones has become widespread throughout the world, and the range of mobile phone contents and services provided includes those used to track the FC/FE of automobiles. In order to analyse real-world FC/FE in Japan with a high level of statistical reliability, the author's group put focus upon the FC/FE management service in which voluntarily reported FC log data of the vehicle users are collected through internet-connected mobile phones across Japan and developed and on-road (actual) FC database. The findings for

Since 2000, the number of brand-new passenger vehicles sold in Japan has fluctuated between 4.26 and 4.76 million, which means that about 8% of the total passenger vehicle fleet was replaced with brand-new vehicles annually. Since the FC/FE of brand-new vehicles improved during this period, it is reasonable to conclude that the FC/FE performance of the passenger vehicle fleet itself should also have improved as these new vehicles replaced older ones. In addition, the mobile phone service provider whose log data were used to develop the actual FC database has reported an increase in the number of users in the 2000s. The author's group therefore updated the database by extending the data collection period from 24 to 54 months and created a database consisting of 1,645,923 pieces of log data collected from October 2000 through March 2005, including information from 49,677 passenger vehicle users on 2,022 models sold in Japan and conducted a statistical analysis of actual FC for passenger HVs and other passenger vehicles with internal combustion engine in Japan (Kudoh et al., 2007; Kudoh et al., 2008). In addition to the previous achievements of the author's group, this paper addresses the effects of vehicle specifications towards the actual FC/FE of passenger According to the revised law, passenger vehicles sold on the Japanese market in 2010 were expected to achieve the FE standard stipulated in the Japanese 10-15 mode driving schedule for each vehicle inertia weight class. The 10-15 mode driving schedule was developed for exhaust measurement and FE tests of light duty vehicles in Japan, including passenger vehicles; the driving pattern and relationship between velocity and acceleration are shown in Figure 1. The test is conducted on a chassis dynamometer with a hot start at curb weight plus 110 [kg] (the approximate weight of 2 passengers), with the air conditioner and other electrical appliances turned off. Figure 2 shows an example of actual vehicle travel activity measured in an urban area (TMGBE, 1996); the average velocity is almost the same in both figures. Although the 10-15 mode driving schedule is supposed to represent actual vehicle travel activity within Japanese urban areas, acceleration and deceleration occurred more frequently under actual conditions and higher levels of acceleration were observed at low velocities. These factors are thought to be among the main reasons for the gap between 10-15 mode FE and actual FE values.

Figure 3 depicts the simulated results of the 10-15 mode FC and the actual FC for a passenger gasoline engine vehicle (GV) with a 2,000 cc displacement. The results were calculated under vehicle driving simulation model (Kudoh et al., 2001). At a similar average velocity (as shown in Figure 2), the actual FC was about 13% lower than predicted by the 10- 15 mode test. In addition, the actual FC of a vehicle clearly varied according to where it was driven, because the main cause of changes in average velocity is the stop-and-go traffic pattern that occurs frequently in urban areas.

As pointed out by Farrington & Rugh (2000) and Nishio et al. (2008), another important factor that should affect the FC/FE gap is the use of air conditioning, because the air conditioning system is turned off in most test cycles on the chassis dynamometer, including in the Japanese 10-15 mode.

**Figure 1.** Japanese 10-15 mode driving schedule.

**Figure 2.** An example of actual vehicle travel activity (TMGBE, 1996).

**Figure 3.** Simulated FC of a passenger vehicle with a 2,000cc gasoline engine.

## **3. Outline of the actual FC database**

Figure 4 outlines the actual FC database that the author's group has been developing based upon the catalogue data of passenger vehicles sold in Japanese market and the voluntarily reported FC log data of vehicle users.

To obtain the passenger vehicle specifications for cars sold in Japan before March 2005, vehicle catalogues for each vehicle name, model year, and model grade were downloaded from an available website on the internet. The vehicle specification database contained information on 35,177 vehicles.

**Figure 4.** Outline of the actual FC database.

220 Internal Combustion Engines

**Figure 2.** An example of actual vehicle travel activity (TMGBE, 1996).

(a) Driving pattern (b) Relationship between

velocity and acceleration

**Figure 3.** Simulated FC of a passenger vehicle with a 2,000cc gasoline engine.

Figure 4 outlines the actual FC database that the author's group has been developing based upon the catalogue data of passenger vehicles sold in Japanese market and the voluntarily

To obtain the passenger vehicle specifications for cars sold in Japan before March 2005, vehicle catalogues for each vehicle name, model year, and model grade were downloaded

**3. Outline of the actual FC database** 

reported FC log data of vehicle users.

The actual FC database was developed by using voluntarily reported FC data from vehicle users and the vehicle specification database. The FC data collection system is called *e-nenpi* (which stands for "electronic FE" in Japanese1); this is an online service for internetconnected mobile phone users2 provided by IID, Inc. The system manages information for vehicle owners, including FC performance and recommended routine maintenance. Users of the service register and provide the following information: (1) zip code of residence, (2) vehicle type3, (3) type of engine air intake (turbocharged/supercharged or normal), (4) transmission type (manual or automatic4), and (5) type of fuel used (unleaded gasoline, premium unleaded gasoline, diesel, or liquefied petroleum gas). Through their mobile phone, the user then enters the amount of fuel put into the vehicle's tank and the odometer reading at the time of fuelling, and the user's FC data are stored on a server.

The items required for service registration were linked with the vehicle specification database and supplemented with other items such that the following 17 attributes were

<sup>1</sup> More information is available at: http://e-nenpi.com (in Japanese).

<sup>2</sup> Although the service was originally provided only for internet-connected mobile phone users, the provider currently offers the service for personal computers as well.

<sup>3</sup> Vehicle type is a code prepared by vehicle makers and approved by the government for vehicles sold and used in Japan to identify each vehicle.

<sup>4</sup> Although the FC may differ depending on the type of automatic transmission, they are grouped together within the database owing to data restrictions.

included in the actual FC database for each user: (1) user ID, (2) base location of where the vehicle was used5, (3) month and year when the vehicle was fuelled, (4) vehicle maker, (5) vehicle name, (6) vehicle type, (7) vehicle class (light passenger vehicle6 (LP) or passenger vehicle (P)), (8) type of powertrain (gasoline vehicle (GV), diesel vehicle (DV) or hybrid vehicle (HV)), (9) type of air intake, (10) transmission type, (11) type of drive system (2WD or 4WD), (12) type of fuel injection engine (direct injection or not), (13) whether a variable valve timing system was used, (14) fuel tank capacity, (15) engine displacement, (16) vehicle kerb weight, and (17) 10-15 mode FE.

Although technological specifications may vary within the same vehicle type by grade or model year owing to differences in equipment or improvement in vehicle technologies, the model year of the vehicle owned by each user could not be specified from the log data. Hence, the following values obtained from the vehicle specification database were used in the technological specifications of a vehicle type in the actual FC database: (1) maximum fuel tank capacity, (2) simple average of minimum and maximum vehicle weight, and (3) simple average of minimum and maximum 10-15 mode FE.

A total of 2,937,780 FC log data points was collected over the 54-month study period (from October 2000 through March 2005). Data were excluded under the following conditions to assure the statistical reliability of the database:


*FEu,v* [km/L], the FE of user *u* who owns vehicle type *v*, was calculated by Equation 1, where *du,v,i* [km] is driving distance from the last fuelling of the *i* th data point, *fu,v,i* [L] is the amount of fuel obtained for data point *i*, and *niu,v* is the number of log data entries.

$$FE\_{u,v} = \sum\_{i \in u, v} (d\_{u,v,i} \mid f\_{u,v,i}) / n\_{i \in u, v} \tag{1}$$

*FEv* [km/L], the FE of vehicle type *v*, was calculated by using Equation 2, where *nu<sup>v</sup>* is the number of users who own *v*.

$$FE\_v = \sum\_{u \cdot vv} FE\_{u,v} / \mathfrak{n}\_{u \cdot vv} \tag{2}$$

Data entries were eliminated from further analysis if they met any of the following conditions:

<sup>5</sup> This was determined from the zip code provided by the registered user.

<sup>6</sup> A light passenger vehicle is equivalent to, or smaller than, the EU's A-segment. Its physical size and engine power are regulated as follows: maximum length, 3.39 [m]; maximum width, 1.48 [m]; maximum height, 2 [m]; maximum engine displacement, 660 [cc]; and maximum engine power, 64 [hp].


kerb weight, and (17) 10-15 mode FE.

simple average of minimum and maximum 10-15 mode FE.

assure the statistical reliability of the database:

database (611,357 entries); and

[L] is the fuel tank capacity.

of fuel obtained for data point *i*, and *ni*

5 This was determined from the zip code provided by the registered user.

displacement, 660 [cc]; and maximum engine power, 64 [hp].

number of users who own *v*.

conditions:

included in the actual FC database for each user: (1) user ID, (2) base location of where the vehicle was used5, (3) month and year when the vehicle was fuelled, (4) vehicle maker, (5) vehicle name, (6) vehicle type, (7) vehicle class (light passenger vehicle6 (LP) or passenger vehicle (P)), (8) type of powertrain (gasoline vehicle (GV), diesel vehicle (DV) or hybrid vehicle (HV)), (9) type of air intake, (10) transmission type, (11) type of drive system (2WD or 4WD), (12) type of fuel injection engine (direct injection or not), (13) whether a variable valve timing system was used, (14) fuel tank capacity, (15) engine displacement, (16) vehicle

Although technological specifications may vary within the same vehicle type by grade or model year owing to differences in equipment or improvement in vehicle technologies, the model year of the vehicle owned by each user could not be specified from the log data. Hence, the following values obtained from the vehicle specification database were used in the technological specifications of a vehicle type in the actual FC database: (1) maximum fuel tank capacity, (2) simple average of minimum and maximum vehicle weight, and (3)

A total of 2,937,780 FC log data points was collected over the 54-month study period (from October 2000 through March 2005). Data were excluded under the following conditions to

b. when users specified a vehicle type that was not included in the vehicle specification

c. when the fuel fill-up rate (*γ*) was less than 60% or more than 100% (536,620 entries). The rate was calculated as *γ = f / C*, where *f* [L] is the amount of fuel put into the tank and *C*

*FEu,v* [km/L], the FE of user *u* who owns vehicle type *v*, was calculated by Equation 1, where *du,v,i* [km] is driving distance from the last fuelling of the *i* th data point, *fu,v,i* [L] is the amount

Data entries were eliminated from further analysis if they met any of the following

6 A light passenger vehicle is equivalent to, or smaller than, the EU's A-segment. Its physical size and engine power are regulated as follows: maximum length, 3.39 [m]; maximum width, 1.48 [m]; maximum height, 2 [m]; maximum engine

*u,v* is the number of log data entries.

, ,, ,, , , ( / )/ *u v i uv uvi uvi i uv FE df n* (1)

, / *<sup>v</sup> u v uv u v FE FE n* (2)

*<sup>v</sup>* is the

a. when the base location of vehicle use could not be specified (21,736 entries);

*FEv* [km/L], the FE of vehicle type *v*, was calculated by using Equation 2, where *nu*


After all of the eliminations, 1,645,923 log data points, including pieces of information from 49,677 users and 2,022 vehicle types, were used to develop the actual FC database. A summary of the number of data points, users, and vehicle types is given in Table 1.



**Table 1.** Data size categories of the actual FC database. The vehicle weight class follows the Japanese inertia weight classes for passenger vehicles. 1 Sampling rate relative to the number of vehicles owned as of March 2005. 2 Sampling rate relative to the number of vehicle types included in the vehicle specification database.

Although Equations 1 and 2 assume that users fill their tanks to the same (full) level at every refuelling, there may be users who do not do so. The *e-nenpi* system recommends that registered users fill up the vehicle tank, and a confirmation message to check whether they have filled up the tank is shown when they input their fuel log through the mobile phone. The second and subsequent log data entries were saved in the server only after a user had confirmed filling up more than twice. In addition, some data were eliminated if they did not satisfy criterion c; the average of fuel fill-up rate of the remaining log data was 76.8% (standard deviation = 8.82%). Users should refuel before the tank was completely empty, indicating that most of the user data included in the actual FC database were acquired as the users filled up at petrol stations, so the fill level of the vehicles was expected to be almost the same every time.

## **4. Vehicle specifications and actual FC/FE**

In the Japanese passenger vehicle market, 12 HV types had been launched as of March 2005; 8 were included in the actual FC database. It is assumed that the FC/FE performance of these vehicles would vary with differences in the powertrain configuration (e.g., series hybrid, parallel hybrid, or power-split hybrid) or degree of hybridisation (such as full hybrid, power-assist hybrid, mild hybrid, or plug-in hybrid). However, because of the difficulties involved in including all of these factors with a high level of statistical reliability, the passenger HV types were combined in this study.

### **4.1. Japanese 10-15 mode and actual FE**

Figure 5 depicts the relationship between the Japanese 10-15 mode FE and actual FE. *FEv,actual* [km/L], the actual FE of vehicle type *v*, was calculated from Equation 3 (USEPA 2010), where *dv,i* and *fv,i* are driving distance [km] and amount of fuel [L] at *i* th log data point of vehicle *v*.

$$FE\_{v,actual} = \sum\_{i \le v} d\_{v,i} / \sum\_{i \le v} f\_{v,i} \tag{3}$$

Table 2 shows the results of a linear regression analysis and the 95% confidential interval (95 CI) described by Equation 4, where *FEv,10-15* [km/L] is the 10-15 mode FE of vehicle *v* .

Understanding Fuel Consumption/Economy of Passenger Vehicles in the Real World 225

$$FE\_{v,actual} = a \cdot FE\_{v,10-15} \tag{4}$$

If a plotted point was on the diagonal line shown in Figure 5, the actual FE of the vehicle was exactly the same as 10-15 mode FE. As can be seen in the figure, the gap between 10-15 mode FE and actual FE increased as the 10-15 mode FE increased.

**Figure 5.** 10-15 mode FE and actual FE.

224 Internal Combustion Engines

specification database.

Vehicle type Number of log data

**4. Vehicle specifications and actual FC/FE** 

passenger HV types were combined in this study.

**4.1. Japanese 10-15 mode and actual FE** 

points

**Table 1.** Data size categories of the actual FC database. The vehicle weight class follows the Japanese inertia weight classes for passenger vehicles. 1 Sampling rate relative to the number of vehicles owned as of March 2005. 2 Sampling rate relative to the number of vehicle types included in the vehicle

Although Equations 1 and 2 assume that users fill their tanks to the same (full) level at every refuelling, there may be users who do not do so. The *e-nenpi* system recommends that registered users fill up the vehicle tank, and a confirmation message to check whether they have filled up the tank is shown when they input their fuel log through the mobile phone. The second and subsequent log data entries were saved in the server only after a user had confirmed filling up more than twice. In addition, some data were eliminated if they did not satisfy criterion c; the average of fuel fill-up rate of the remaining log data was 76.8% (standard deviation = 8.82%). Users should refuel before the tank was completely empty, indicating that most of the user data included in the actual FC database were acquired as the users filled up at petrol stations, so the fill level of the vehicles was expected to be almost the same every time.

In the Japanese passenger vehicle market, 12 HV types had been launched as of March 2005; 8 were included in the actual FC database. It is assumed that the FC/FE performance of these vehicles would vary with differences in the powertrain configuration (e.g., series hybrid, parallel hybrid, or power-split hybrid) or degree of hybridisation (such as full hybrid, power-assist hybrid, mild hybrid, or plug-in hybrid). However, because of the difficulties involved in including all of these factors with a high level of statistical reliability, the

Figure 5 depicts the relationship between the Japanese 10-15 mode FE and actual FE. *FEv,actual* [km/L], the actual FE of vehicle type *v*, was calculated from Equation 3 (USEPA 2010), where *dv,i* and *fv,i* are driving distance [km] and amount of fuel [L] at *i* th log data point of vehicle *v*.

Table 2 shows the results of a linear regression analysis and the 95% confidential interval (95

CI) described by Equation 4, where *FEv,10-15* [km/L] is the 10-15 mode FE of vehicle *v* .

, , , / *v actual v i v i iv iv FE d f* (3)

1,266 – 1,515 kg 671 43 1 1,766 – 2,015 kg 1,447 51 1 2,016 – 2,265 kg 366 20 1

Total 1,645,923 49,677 (0.089%1) 2,022 (40.5%2)

Total 5,384 216 (0.111%1) 8 (57.1%2)

Number of users Number of vehicle

types


**Table 2.** Estimates of parameters by Equation 4. *t* is the t statistics.

25 P-GVs had an actual FE that was higher than the corresponding 10-15 mode FE. (These are above the line in Figure 5.) Figure 6 shows the achievement ratio of actual FE to 10-15 mode FE of domestically produced and imported P-GVs; 23 out of the 25 P-GVs with a ratio of greater than 1 were imported vehicles. These results indicate that the achievement ratio of actual FE to 10-15 mode FE may be higher for imported vehicles than for domestically produced vehicles. The results of a two-tailed Welch test confirmed that the mean achievement ratios of domestically produced passenger vehicles (*x*) were significantly lower than those of imported passenger vehicles (*y*) (mean of *x = 0.758*, variance of *x = 0.00445*, mean of *y = 0.854*, variance of *y = 0.00810*, *T = 15.1*, degree of freedom *= 268*; *p < 0.05*). One possible explanation is that the drivetrains or transmissions of imported vehicles are not optimised for Japanese road conditions and their 10-15 mode FEs tend to be lower than their counterpart domestically produced P-GVs.

**Figure 6.** Comparison of domestically produced P-GVs and imported P-GVs.

### **4.2. Vehicle weight and actual FC**

Weight-saving technologies in passenger vehicles will play an important role in improving FC, along with improvements in engine and drivetrain efficiency. Figure 7 depicts the relationship between vehicle weight and actual FC. Here, *FCv,actual* [L/100 km], the actual FC of vehicle type *v*, is calculated by Equation 5.

$$FC\_{v,actual} = 100 \cdot \sum\_{i \le v} f\_{v,i} / \sum\_{i \le v} d\_{v,i} \tag{5}$$

Two FC standards are shown in Figure 7: the Japanese 2010 standard for GVs and the 2005 standard for DVs. Points plotted above the two lines represent vehicles that do not achieve the FC standards in the real world. Although most brand-new passenger vehicles were announced to have achieved the FC standard by 2005, Figure 7 reveals that only some P-DVs and all the P-HVs achieved the Japanese FC standard in the real world at that time.

Since *FCv,actual* can be thought to be proportional to vehicle weight *w* [kg], a linear regression analysis was conducted by using Equation 6 (Table 3).

$$FC\_{\upsilon,actual} = b \cdot \varpi + c \tag{6}$$

The analysis showed that it is difficult to explain the FC of LP-GVs and P-DVs only by vehicle weight. Sales of brand-new LP-GVs, which are restricted in terms of vehicle size and engine displacement, are rapidly expanding in Japan, and Japanese vehicle makers provide a variety of vehicle types (e.g., hatchbacks and wagons) within the regulatory standard. To compensate for the increase in vehicle weight incurred by equipment installed to meet consumer needs or to satisfy safety standards, many LP-GVs use turbochargers. Including only LP-GVs that were introduced to the market after 1998 (when the LP vehicle standards were changed to meet new crash safety standards), the engine displacement of LP-GVs were from 657 – 660 [cc] but their average vehicle weight was 842 [kg] with a wide variation from 550 and 1,060 kg. As a result, the FC differs owing to differences in running resistance (attributed mainly to differences in vehicle shape), transmission type, drive system, and turbocharging, which result in the low *R2* value (0.471).

226 Internal Combustion Engines

counterpart domestically produced P-GVs.

**4.2. Vehicle weight and actual FC** 

of vehicle type *v*, is calculated by Equation 5.

analysis was conducted by using Equation 6 (Table 3).

**Figure 6.** Comparison of domestically produced P-GVs and imported P-GVs.

Weight-saving technologies in passenger vehicles will play an important role in improving FC, along with improvements in engine and drivetrain efficiency. Figure 7 depicts the relationship between vehicle weight and actual FC. Here, *FCv,actual* [L/100 km], the actual FC

(a) 10-15 mode FE and actual FE (b) Achievement ratio of

Two FC standards are shown in Figure 7: the Japanese 2010 standard for GVs and the 2005 standard for DVs. Points plotted above the two lines represent vehicles that do not achieve the FC standards in the real world. Although most brand-new passenger vehicles were announced to have achieved the FC standard by 2005, Figure 7 reveals that only some P-DVs and all the P-HVs achieved the Japanese FC standard in the real world at that time.

Since *FCv,actual* can be thought to be proportional to vehicle weight *w* [kg], a linear regression

The analysis showed that it is difficult to explain the FC of LP-GVs and P-DVs only by vehicle weight. Sales of brand-new LP-GVs, which are restricted in terms of vehicle size and engine displacement, are rapidly expanding in Japan, and Japanese vehicle makers provide

, , , 100 / *v actual v i v i iv iv FC f d* (5)

actual FE to 10-15 mode FE

*v actual* , *FC b w c* (6)

achievement ratios of domestically produced passenger vehicles (*x*) were significantly lower than those of imported passenger vehicles (*y*) (mean of *x = 0.758*, variance of *x = 0.00445*, mean of *y = 0.854*, variance of *y = 0.00810*, *T = 15.1*, degree of freedom *= 268*; *p < 0.05*). One possible explanation is that the drivetrains or transmissions of imported vehicles are not optimised for Japanese road conditions and their 10-15 mode FEs tend to be lower than their


**Table 3.** Estimates of parameters by Equation 6. *n* is sample number, *B* is partial regression coefficient and *t* is t statistics, respectively.

Of the 113 P-DVs plotted in Figure 7, 25 are 4WD, 92 have AT/CVT transmission, 108 are turbocharged, and 11 have a direct injection engine. The vehicle weight range of 1,705— 2,165 [kg] is small compared with that of P-GVs (715—2,380 [kg]). The low *R2* value (0.336) for P-DVs indicate that it is difficult to explain actual FC only with vehicle weight, for the actual FC of a vehicle varies by the combinations of various vehicle specifications.

## **4.3. Effect of vehicle technologies on actual FC of gasoline-fuelled passenger vehicles**

A multiple regression analysis was conducted to evaluate the effect of vehicle technologies on the actual FC of gasoline-fuelled passenger vehicles (P-GVs and P-HVs). A P-GV with a manual transmission and 2WD was set as the baseline. The regression equation can be described as Equation 7:

$$\begin{aligned} FC\_{v,actual} &= -d\_0 + d\_1 w + d\_2 D\_{HV} + d\_d D\_{AT/CVT} \\ &+ d\_4 D\_{TC} + d\_5 D\_{4\text{VD}} + d\_6 D\_{DI} + d\_7 D\_{VVT} \end{aligned} \tag{7}$$

where *w* is vehicle weight [kg] and *DHV*, *DAT/CVT*, *DTC*, *D4WD*, *DDI*, and *DVVT* are the dummy variables for P-HV, transmission (AT/CVT), turbocharging (TC), 4WD, direct injection (DI), and variable valve timing (VVT), respectively. The parameter estimates are summarized in Table 4.

**Figure 7.** Vehicle weight and actual FC

Using the estimates shown in Table 4 and Equation 7, it is confirmed that the use of direct injection and variable valve timing led to a decrease in actual FC, whereas the use of an automatic transmission and turbocharging resulted in an increase in actual FC. Although the partial regression coefficients of HV and 4WD are negative, adding hybrid technology and 4WD to a baseline P-GV increased vehicle weight. Hence, to evaluate the effect of hybridisation and 4WD, the balance between vehicle weight increase and the coefficients of the dummy variables given in Table 4 should be considered.

Among the 8 HV models included in the actual FC database, 3 models also had equivalent GVs within the same vehicle name, 3 had engines that were variants of the GV models, and 2 were dedicated HV models. Therefore, counterpart GV models could be defined for 6 of the 8 HV models. Although the vehicle weight of HVs depends upon various vehicle specifications, the weight increase of these 6 HVs from their counterpart GVs ranged from 40 to 195 [kg]. Equation 7 and Table 4 were then used to estimate a 0.336—1.64 [L/100km] increase in actual FC from hybridisation. Because the actual FC improvement effect evaluated from the partial regression coefficient of HV prevailed in this estimate, however, it is estimated that hybridisation contributed to an actual FC improvement (-4.44 to -3.14 [L/100km]) from the baseline P-GV.

Of the 1,615 samples analysed in this section, 370 had the same vehicle name and model year for both 2WD and 4WD models (other specifications, such as transmission type, turbocharging, and direct injection, were the same). The use of 4WD increased weight by 83.1 [kg] on average (standard deviation = 38.8 [kg]). The partial regression coefficients *d1* and *d5* shown in Table 4 indicate that a weight increase of 83.1 kg would result in an actual FC increase of 0.329 [L/100km].

228 Internal Combustion Engines

**Figure 7.** Vehicle weight and actual FC

[L/100km]) from the baseline P-GV.

the dummy variables given in Table 4 should be considered.

Using the estimates shown in Table 4 and Equation 7, it is confirmed that the use of direct injection and variable valve timing led to a decrease in actual FC, whereas the use of an automatic transmission and turbocharging resulted in an increase in actual FC. Although the partial regression coefficients of HV and 4WD are negative, adding hybrid technology and 4WD to a baseline P-GV increased vehicle weight. Hence, to evaluate the effect of hybridisation and 4WD, the balance between vehicle weight increase and the coefficients of

Among the 8 HV models included in the actual FC database, 3 models also had equivalent GVs within the same vehicle name, 3 had engines that were variants of the GV models, and 2 were dedicated HV models. Therefore, counterpart GV models could be defined for 6 of the 8 HV models. Although the vehicle weight of HVs depends upon various vehicle specifications, the weight increase of these 6 HVs from their counterpart GVs ranged from 40 to 195 [kg]. Equation 7 and Table 4 were then used to estimate a 0.336—1.64 [L/100km] increase in actual FC from hybridisation. Because the actual FC improvement effect evaluated from the partial regression coefficient of HV prevailed in this estimate, however, it is estimated that hybridisation contributed to an actual FC improvement (-4.44 to -3.14

Of the 1,615 samples analysed in this section, 370 had the same vehicle name and model year for both 2WD and 4WD models (other specifications, such as transmission type, turbocharging, and direct injection, were the same). The use of 4WD increased weight by


**Table 4.** Estimates of parameters by Equation 7. *n* is sample number, *B* is partial regression coefficient and *t* is t statistics, respectively.

## **5. Annual differences in mean actual FC of gasoline-fuelled passenger vehicles**

Annual (fiscal year, FY) changes in vehicle weight and actual FC for gasoline-fuelled passenger vehicles from FY 2001 to 2004 are analysed. Table 5 presents the descriptive statistics of vehicle weight for gasoline-fuelled passenger vehicles (P-GVs and P-HVs) that were used to conduct a one-factor analysis of variance. No significant difference was observed for mean vehicle weight of P-HVs (*F* = 0.252, *p* = 0.859), but a significant difference was found for P-GVs (*F* = 2.71, *p* = 0.044). Therefore, a post-hoc multiple comparison by Sheffé's test on vehicle weight of P-GVs was conducted, but no significant differences were observed.

Similarly, the mean differences of actual FC are tested. As shown in Section 4.2, actual FC is presented as proportional to vehicle weight; therefore, an analysis of covariance was carried out to adjust for the effect of vehicle weight in actual FC. Mean actual FC of P-GVs decreased significantly from FY2001 until FY2004 (*F* = 19.7, *p* = 0.000). Post-hoc multiple comparisons with the Sidak adjustment showed that the mean actual FC values adjusted for vehicle weight were significantly different, except between FY2003 and FY2004 (Table 6). No significant differences were observed for P-HVs (*F* = 0.299, *p* = 0.826).

The results indicate that the actual FC of P-GVs included in the actual FC database steadily improved, most likely as a result of an increase in the number of vehicles equipped with FCimproving technologies and not because of weight reductions. The lack of significant changes for P-HVs can be attributed to the fact that only small numbers of new-type P-HVs had entered the Japanese passenger vehicle fleet at the time of the study and also to a lack of drastic improvements in the P-HVs produced during this period.


**Table 5.** Descriptive statistics of vehicle weight [kg]. *n* is the number of vehicle types, *μ* is the population mean, and *σ* is standard deviation.


**Table 6.** Results of post-hoc multiple comparisons using the Sidak adjustment for the mean actual FC of P-GVs. The value in each cell shows the differential in the population mean *μr* in rowwise group *r* and *μc* in columnwise group *c*. For example, *μFY2001* – *μFY2002* = 0.190. Asterisk denotes significance at 5% level.

## **6. Validity of actual FC obtained from the actual FC database**

To check the validity of the actual FC values calculated from the database, two cases from the database were compared with a third that was calculated from published statistics for gasoline-fuelled passenger vehicles (P-GVs and P-HVs):

Case A: The actual FC of gasoline-fuelled passenger vehicles was estimated for each FY directly from the database.

Case B: The actual FC of gasoline-fuelled passenger vehicles was estimated from the results of the regression analysis between vehicle weight and actual FC (Table 7, Equation 6) and the estimated number of vehicles owned, by vehicle weight (by 10 kg increments), for each FY.

Case C: The actual FC of gasoline-fuelled passenger vehicles was estimated from national statistics (MLIT, 2003–2005).

For Case B, the number of vehicles owned by vehicle weight was estimated from the vehicle specification database and various published statistics (AIRIA1, 2003–2005; AIRIA2, 2003– 2005; AIRIA3, 2003–2005). Figure 8 shows the ownership rate (OR) relative to the total number of vehicles owned, by Japanese inertia weight class, for passenger vehicles from FY2002 (March 2003) to FY2004 (March 2005). The sampling rate (SR) — the number of vehicles actually included in the estimates of Case A as a ratio of the total number of vehicles owned — is also shown in the figure. The vehicle weight distribution of the database (SR) does not reflect the real-world distribution (OR); OR has a normal distribution, whereas SR is higher for both light (< 702 [kg]) and heavy (1,766+ [kg]) vehicles. Therefore, actual FC values compiled directly from the database in Case A might have been biased as a result of the vehicle weight distribution.

230 Internal Combustion Engines

population mean, and *σ* is standard deviation.

P-GV P-HV *n μ σ n μ σ*

2001 970 1,330.92 268.04 5 1,196.00 415.73 2002 1,073 1,342.16 275.34 4 1,290.00 414.17 2003 1,091 1,353.79 272.29 7 1,378.57 410.15 2004 1,089 1,362.95 269.70 7 1,378.57 410.15 All 4,223 1,347.94 271.70 23 1,323.48 390.39

**Table 5.** Descriptive statistics of vehicle weight [kg]. *n* is the number of vehicle types, *μ* is the

**6. Validity of actual FC obtained from the actual FC database** 

gasoline-fuelled passenger vehicles (P-GVs and P-HVs):

directly from the database.

statistics (MLIT, 2003–2005).

[L/100km] FY2002 FY2003 FY2004 FY2001 0.190\* 0.403\* 0.441\* FY2002 0.213\* 0.251\* FY2003 0.038 **Table 6.** Results of post-hoc multiple comparisons using the Sidak adjustment for the mean actual FC of P-GVs. The value in each cell shows the differential in the population mean *μr* in rowwise group *r* and *μc* in columnwise group *c*. For example, *μFY2001* – *μFY2002* = 0.190. Asterisk denotes significance at 5%

To check the validity of the actual FC values calculated from the database, two cases from the database were compared with a third that was calculated from published statistics for

Case A: The actual FC of gasoline-fuelled passenger vehicles was estimated for each FY

Case B: The actual FC of gasoline-fuelled passenger vehicles was estimated from the results of the regression analysis between vehicle weight and actual FC (Table 7, Equation 6) and the estimated number of vehicles owned, by vehicle weight (by 10 kg increments), for each

Case C: The actual FC of gasoline-fuelled passenger vehicles was estimated from national

For Case B, the number of vehicles owned by vehicle weight was estimated from the vehicle specification database and various published statistics (AIRIA1, 2003–2005; AIRIA2, 2003– 2005; AIRIA3, 2003–2005). Figure 8 shows the ownership rate (OR) relative to the total number of vehicles owned, by Japanese inertia weight class, for passenger vehicles from FY2002 (March 2003) to FY2004 (March 2005). The sampling rate (SR) — the number of vehicles actually included in the estimates of Case A as a ratio of the total number of

FY

level.

FY.

**Figure 8.** Ownership rates of gasoline-fuelled passenger vehicles and sampling rates of vehicles included in the database.

As described in Section 4, the mean actual FC adjusted by vehicle weight improved each year in the study period. Therefore, Case B was designed to reflect improvements in actual FC adjusted for the vehicle weight bias that might have been included in the database (Case A). Because no significant improvement in actual FC was observed for P-HVs from FY2002 to FY2004, the results of the regression analysis shown in Table 3 were used for P-HVs; the results from Table 7 were used for P-GVs.

Table 8 shows the estimates of actual FC of gasoline-fuelled passenger vehicles for the three cases from FY2002 to FY2004. The actual FC steadily improved from FY2002 to FY2004 in Cases A and C, but the actual FC did not improve from FY2003 and FY2004 in Case B, similar to the results in the same time period shown in Table 6. Although there are small differences in each FY, the estimates of actual FC of gasoline-fuelled passenger vehicles in Cases A and B were within 4% of the Case C estimates in all instances. Therefore, the actual FC values derived from the database appear to be compatible with the estimates from published statistics.


**Table 7.** Estimates of parameters by Equation 4 for P-GVs for FY2002–2004. *n* is sample number, *B* is partial regression coefficient and *t* is t statistics, respectively.


**Table 8.** Comparison of actual FC [L/100km] of gasoline-fuelled passenger vehicles for Cases A–C.

## **7. Conclusion**

In order to quantify the relationship between vehicle specifications and actual FC with statistical reliability, an actual FC database was developed by using vehicle specification data and voluntarily reported data collected from an internet-connected mobile phone system throughout Japan. The database was used to conduct statistical analyses to evaluate the effects of various vehicle specifications on the FC/FE of passenger vehicles. The actual FC adjusted by vehicle weight was shown to have significantly improved from FY2001 to FY 2004. Moreover, estimates of the actual FC of gasoline-fuelled passenger vehicles obtained from the database were consistent with estimates calculated from national statistics.

With the revision of the Energy-Saving Law in July 2007, Japan changed from using the 10- 15 mode to the JC08 mode (UNEP, 2012); the new 2015 FE standards for passenger vehicles are based on the Top Runners Approach provided in the JC08 mode. Japanese vehicle makers have already started to sell new passenger vehicles that have achieved the 2015 FE standard, so the effects of equipping vehicles with various types of new and more fuel efficient technologies may influence the actual FC of these vehicles as well. The author's group plans to extend the data collection period presented in this paper and to update the actual FC database to reflect state-of-the-art vehicle technologies in the real world.

Finally, the World Forum for Harmonization of Vehicle Regulations, which is a working party (WP.29) of the United Nations Economic Commission for Europe, has decided to set up an informal group under its Working Party on Pollution and Energy to develop a worldwide harmonized light duty test cycle (the Worldwide Harmonized Light Duty Vehicle Test Procedures, WLTP) by 2013. This cycle will represent typical driving conditions around the world (UNECE, 2012). Because the actual FC/FE of vehicles might show different trends if the WLTP is adopted and applied to meet new FC/FE standards, the movement towards the endorsement of the WLTP could influence future studies as well.

## **Author details**

232 Internal Combustion Engines

*B*  (95 CI)

> Case B (95CI)

Case B / Case C (95 CI)

**7. Conclusion** 

*b*

8.57 (8.25 – 8.88)

*10-3 c b*

partial regression coefficient and *t* is t statistics, respectively.

0.338 (-0.0910 – 0.767)

11.36 (11.24 – 11.48)

0.974 (0.964 – 0.984)

 FY2002 FY2003 FY2004 *n* 1,073 1,091 1,089 *R2* 0.729 0.704 0.684

8.38 (8.06 – 8.70)

*t* 53.7 1.55 50.9 1.66 48.5 1.71

**Table 7.** Estimates of parameters by Equation 4 for P-GVs for FY2002–2004. *n* is sample number, *B* is

Case or comparison FY2002 FY2003 FY2004 Case A 11.81 11.62 11.59

Case C 11.66 11.49 11.13 Case A / Case C 1.01 1.01 1.04

**Table 8.** Comparison of actual FC [L/100km] of gasoline-fuelled passenger vehicles for Cases A–C.

from the database were consistent with estimates calculated from national statistics.

actual FC database to reflect state-of-the-art vehicle technologies in the real world.

With the revision of the Energy-Saving Law in July 2007, Japan changed from using the 10- 15 mode to the JC08 mode (UNEP, 2012); the new 2015 FE standards for passenger vehicles are based on the Top Runners Approach provided in the JC08 mode. Japanese vehicle makers have already started to sell new passenger vehicles that have achieved the 2015 FE standard, so the effects of equipping vehicles with various types of new and more fuel efficient technologies may influence the actual FC of these vehicles as well. The author's group plans to extend the data collection period presented in this paper and to update the

In order to quantify the relationship between vehicle specifications and actual FC with statistical reliability, an actual FC database was developed by using vehicle specification data and voluntarily reported data collected from an internet-connected mobile phone system throughout Japan. The database was used to conduct statistical analyses to evaluate the effects of various vehicle specifications on the FC/FE of passenger vehicles. The actual FC adjusted by vehicle weight was shown to have significantly improved from FY2001 to FY 2004. Moreover, estimates of the actual FC of gasoline-fuelled passenger vehicles obtained

*10-3 c b*

11.23 (11.10 – 11.36)

0.977 (0.966 – 0.988)

0.377 (0.0692 – 0.822)

8.33 (7.99 – 8.67)

*10-3 c* 

11.24 (11.11 – 11.37)

1.01 (0.998 – 1.02)

0.408 (0.0599 – 0.876)

> Yuki Kudoh *Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology, Japan*

## **8. References**

An F., Earley, R. & Green-Weiskel, L. (May 2011). Global Overview on Fuel Efficiency and Motor Vehicle Emission Standards: Policy Options and Perspectives for International Cooperation, United Nations Commission of Sustainable Development, Background Document CSD19/2011/BP3. Retrieved from

<http://www.un.org/esa/dsd/resources/res\_pdfs/csd-19/Background-paper3-transport.pdf> Automobile Inspection & Registration Information Association (AIRIA1) (2003–2005).

*Number of Vehicles Owned by Vehicle Weight as of March Each Year*, (in Japanese)


<http://www.epa.gov/otaq/cert/mpg/fetrends/420r10023.pdf>

Wang, H., Fu, L, Zhou, Y. & Li, H. (2008). Modelling of the fuel consumption for passenger cars regarding driving characteristics, *Transportation Research Part D: Transport and Environment*, Vol. 13, Issue 7, (October 2008), pp.479-482, ISSN 1361-9209

Kudoh, Y., Kondo, Y., Matsuhashi, K., Kobayashi, S. & Moriguchi, Y. (2004). Current status of actual fuel-consumptions of petrol-fuelled passenger vehicles in Japan, *Applied* 

Kudoh, Y., Matsuhashi, K., Kondo, Y., Kobayashi, S. Moriguchi, Y. & Yagita, H. (2007). Statistical Analysis of Fuel Consumption of Hybrid Electric Vehicles in Japan, *The World* 

Kudoh, Y., Matsuhashi, K., Kondo, Y., Kobayashi, S. Moriguchi, Y. & Yagita, H. (2008). Statistical Analysis on the Transition of Actual Fuel Consumption by Improvement of Japanese 10•15 Mode Fuel Consumption, *Journal of the Japan Institute of Energy*, Vol. 87,

Ministry of Land, Transport and Infrastructures (MLIT) (2003–2005). *Annual Statistics of* 

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## *Edited by Kazimierz Lejda and Pawel Wos*

This book on internal combustion engines brings out few chapters on the research activities through the wide range of current engine issues. The first section groups combustion-related papers including all research areas from fuel delivery to exhaust emission phenomena. The second one deals with various problems on engine design, modeling, manufacturing, control and testing. Such structure should improve legibility of the book and helps to integrate all singular chapters as a logical whole.

Internal Combustion Engines

Internal Combustion Engines

*Edited by Kazimierz Lejda and Pawel Wos*

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