**4.1. Characteristics of the research objects and testing methods**

Two vehicles were selected for the evaluation of the start-stop system. Vehicle A was fitted with a turbocharged gasoline engine of the displacement of 0.9 dm3 , fitted with a three-way catalytic converter (**Table 2** and **Figure 7**). The engine was characterized with a volumetric power output index of 70.8 kW/dm3 . Vehicle B was fitted with a diesel engine of the displacement of 3.0 dm3 . In this case, the volumetric power output index amounted to 58.7 kW/dm3 and was lower by 17% than the index of vehicle A. The engine of this vehicle was fitted with a diesel oxidation catalyst (DOC) and a diesel particulate filter.

## **4.2. Testing methods**

Exhaust emission tests (CO2 , NOx , CO, and THC) were performed under real operating conditions of the vehicle in traffic in the Poznań city. The vehicle route during the tests has been shown in **Figure 8**.

The length of the route was 12.71 km. It was diversified and included a typical urban portion and an extra-urban portion where it was possible to drive at highway speeds (with a maximum speed of 120 km/h). The extra-urban portion was 5.5 km long. As shown in **Figure 8**, the length of the vehicle route during the road test was similar to that of the NEDC test [3]. The driving time in the road tests of approximately 1200 s was similar to that of the NEDC test.


**Table 2.** Characteristics of the tested objects.

**Figure 6.** Engine parameters in different emission tests [22].

**Table 1.** Characteristics of the NEDC and WLTC emission tests [20, 21].

of constant accelerations (**Table 1**).

106 Improvement Trends for Internal Combustion Engines

Maximum acceleration [m/s2

For the Class 1 vehicles, the worldwide harmonized light-duty test cycle (WLTC) test is composed of three parts representing the driving conditions with two low and medium speed (**Figure 5a**). Its maximum value is 49.1 and 64.4 km/h, respectively. The average speed in the entire cycle is 33.3 km/h (counted without vehicle stationary) or 26.8 km/h including the vehicle stops that total 21.1% of the entire test duration. The test designed for Class 2 vehicles has an additional phase representing high speeds (**Figure 5b**). Its total time amounts to 1800 s and the vehicle covers a distance of 22.649 km. The values of the maximum and average speeds are different than those of the Class 1 vehicles. The most complex is the WLTC test for Class 3 vehicles (**Figure 5c**). It is composed of four phases. In the final part of the test, the vehicle develops a speed of 131.3 km/h [22]. In relation to the NEDC test, it is a 10% increase. The total WLTC test time for this class of vehicles is 1800 s. Comparing the WLTC test with the NEDC one, we can see a fundamental difference related to the velocity curve—the NEDC test is composed of repeated segments, while the WLTC tests have different velocity profiles that are a representation of the actual driving cycle. High variability of acceleration is a characteristic of these tests compared to the NEDC test

Time [s] 1180 1611 1800 1800 Distance [m] 11,023 11,428 22,649 23,262 Share of vehicle stationary [%] 33 21.1 15.8 13.4 Maximum speed [km/h] 120 64.4 123.1 131.4 Average speed [km/h] 33.6 26.8 50.4 51.8

**NEDC WLTC Class 1 WLTC Class 2 WLTC Class 3**

] 1 0.76 0.96 1.58

**Figure 7.** The tested objects ready for the on-road exhaust emissions tests.

## **4.3. Analysis of the exhaust emissions from LDV vehicles**

In order to determine the efficiency of the start-stop system, the exhaust emission measurements were performed for the system in the enabled and disabled mode. Average speed was selected as a criterion decisive of the possibility of comparison of both vehicle drives. Its maximum relative difference was assumed on the level of 5%. For vehicle A, the relative speed difference was 3.5% and for vehicle B—5%.

Based on the data recorded from the OBD system of the vehicles, the operating time share characteristics of the vehicle engines were made depending on the engine speed and torque (**Figure 9**). In the case of vehicle A, due to the start-stop system, as much as 11% of the driving

**Figure 9.** Characteristics of the operating time share referred to the engine (a) of vehicle A and (b) of vehicle B.

**Figure 10** presents the changes in the exhaust emissions measured with the second-by-

during a drive with the start-stop system enabled. Having analyzed the obtained courses, we have observed that the system switched off the engine seven times. The effect of this

, CO, THC) and the engine speed on the example of vehicle B

Measurement of Exhaust Emissions under Actual Operating Conditions with the Use of PEMS...

http://dx.doi.org/10.5772/intechopen.70442

109

at that time. It has also been observed that in the first

, CO, and THC measured with the second-by-second resolution and

time, the engine was off and for vehicle B it was 6%.

, NOx

second resolution (CO2

was obviously zero emission of CO2

**Figure 10.** The courses of the emissions of CO2

, NOx

engine speed of vehicle B during a drive with the start-stop system enabled.

**Figure 8.** The road used for the exhaust emission testing (marked with red line) [created by GPSVisualizer.com].

**Figure 9.** Characteristics of the operating time share referred to the engine (a) of vehicle A and (b) of vehicle B.

**4.3. Analysis of the exhaust emissions from LDV vehicles**

**Figure 7.** The tested objects ready for the on-road exhaust emissions tests.

difference was 3.5% and for vehicle B—5%.

108 Improvement Trends for Internal Combustion Engines

In order to determine the efficiency of the start-stop system, the exhaust emission measurements were performed for the system in the enabled and disabled mode. Average speed was selected as a criterion decisive of the possibility of comparison of both vehicle drives. Its maximum relative difference was assumed on the level of 5%. For vehicle A, the relative speed

**Figure 8.** The road used for the exhaust emission testing (marked with red line) [created by GPSVisualizer.com].

Based on the data recorded from the OBD system of the vehicles, the operating time share characteristics of the vehicle engines were made depending on the engine speed and torque (**Figure 9**). In the case of vehicle A, due to the start-stop system, as much as 11% of the driving time, the engine was off and for vehicle B it was 6%.

**Figure 10** presents the changes in the exhaust emissions measured with the second-bysecond resolution (CO2 , NOx , CO, THC) and the engine speed on the example of vehicle B during a drive with the start-stop system enabled. Having analyzed the obtained courses, we have observed that the system switched off the engine seven times. The effect of this was obviously zero emission of CO2 at that time. It has also been observed that in the first

**Figure 10.** The courses of the emissions of CO2 , NOx , CO, and THC measured with the second-by-second resolution and engine speed of vehicle B during a drive with the start-stop system enabled.

half of the test (0–600 s), the maximum values of the emission of CO2 were lower than in the second part of the test. This depended on the characteristics of the test route—the second part of the test was a drive close to the extra-urban traffic conditions (a road portion of the entrance to the city). On this road portion, higher speeds were developed, which resulted in an increased energy demand of the engine, hence a growth in the emission of CO2 . In the case of the emission of NOx and CO, a similar situation has been observed. The highest level of the emission of THC occurred in the first phase of the test. This most likely resulted from a cold engine start—lower temperature of the catalytic converter. We can deduct that the DOC catalyst in the beginning of the test did not reach the light-off temperature.

For vehicle B, a reduction has been recorded of:

by 11%;

by 10%;

that are not always considered during laboratory tests.

dynamic operating parameters (**Figure 13**).

additional division into regular standards and EEV.

by 10%; and

**5. Exhaust emissions legislation for engines of HDV vehicles**

unit emissions of individual exhaust components was: CO—67%, HC—88%, NOx

The obtained results confirm the efficiency of the application of the start-stop system. It is worth emphasizing that the presented results reflect the actual benefits from the application of this system as the tests were performed in actual traffic; hence, certain operating factors having impact on the exhaust emissions and fuel consumption were taken into account—factors

Measurement of Exhaust Emissions under Actual Operating Conditions with the Use of PEMS...

http://dx.doi.org/10.5772/intechopen.70442

111

For the HDV group of vehicles, due to their specific design characterized by significant size and power outputs, homologation in terms of unit emissions is performed for the engine alone on engine test beds. For all Euro standards, performing tests at preset points of work in stationary tests is necessary. Since 2000, the Euro III standard is applicable for the homologated vehicles. It is based on: European transient cycle (ETC), European stationary cycle (ESC), and European load response (ELR). The same procedures are applicable for the Euro IV, V, and EEV standards, but the exhaust opacity test for heavy-duty vehicles is performed in the ELR test. The boundary values of the exhaust emissions for diesel engines have been reduced with the introduction of further directives and regulations (**Figure 12**). A relative reduction of the

particulate mass—98%, respectively. For exhaust opacity, limits were applicable throughout the Euro III–V standards. Following the technological advancement of combustion engines and aftertreatment systems, an introduction of boundary values [particle number (PN)] in the Euro VI became necessary. Along with the introduction of the Euro III standard, an European transient cycle (ETC) became applicable in which the combustion engine was tested for

In the Euro VI standard, in relation to the previous regulations, requirements related to the diesel engine have been more extensively defined. The latest regulations do not allow for the

During the development of the transient *World harmonized transient cycle* (WHTC) and stationary *World harmonized stationary cycle* (WHSC), road test results performed in selected EU member states, Japan and USA were taken into account. This aimed at approximating the test bed measurement cycles to the actual conditions of operation worldwide. The

—95%, and

• the emission of CO2

• the emission of NOx

• gas mileage by 12%.

• the emission of CO by 13%;

• the emission of HC + NOx

Based on the performed measurements, the on-road emissions of CO2 , NOx , CO, THC, HC + NOx as well as gas mileage were determined. The obtained values were compared to the limits set forth in the Euro 5 standard (**Figure 11**). The authors also determined the efficiency of the applied start-stop system. For vehicle A, the enabling of the system resulted in a reduction of:


**Figure 11.** The obtained on-road emissions of NOx , CO, THC, and HC + NOx referred to the limits determined in the Euro 5 standard.

For vehicle B, a reduction has been recorded of:


**Figure 11.** The obtained on-road emissions of NOx

Euro 5 standard.

CO2

temperature.

• the emission of CO2

• the emission of NOx

• gas mileage by 9%.

• the emission of CO by 12%;

• the emission of THC by 15%; and

, CO, THC, and HC + NOx

half of the test (0–600 s), the maximum values of the emission of CO2

Based on the performed measurements, the on-road emissions of CO2

. In the case of the emission of NOx

110 Improvement Trends for Internal Combustion Engines

by 7%;

by 13%;

the second part of the test. This depended on the characteristics of the test route—the second part of the test was a drive close to the extra-urban traffic conditions (a road portion of the entrance to the city). On this road portion, higher speeds were developed, which resulted in an increased energy demand of the engine, hence a growth in the emission of

The highest level of the emission of THC occurred in the first phase of the test. This most likely resulted from a cold engine start—lower temperature of the catalytic converter. We can deduct that the DOC catalyst in the beginning of the test did not reach the light-off

as well as gas mileage were determined. The obtained values were compared to the limits set forth in the Euro 5 standard (**Figure 11**). The authors also determined the efficiency of the applied

start-stop system. For vehicle A, the enabling of the system resulted in a reduction of:

referred to the limits determined in the

were lower than in

, CO, THC, HC + NOx

and CO, a similar situation has been observed.

, NOx

The obtained results confirm the efficiency of the application of the start-stop system. It is worth emphasizing that the presented results reflect the actual benefits from the application of this system as the tests were performed in actual traffic; hence, certain operating factors having impact on the exhaust emissions and fuel consumption were taken into account—factors that are not always considered during laboratory tests.
