**Abstract**

Use of detailed chemistry augments the combustion model of a three-dimensional unsteady compressible turbulent Navier–Stokes solver with liquid spray injection when coupled with fluid mechanics solution with detailed kinetic reactions. Reduced chemical reaction mechanisms help in the reducing the simulations time to study of the engine performance parameters, such as, in-cylinder pressure in spark ignition engines. Sensitivity analysis must be performed to reduce the reaction mechanism for the compression and power strokes utilizing computational singular perturbation (CSP) method. To study a suitable well-established surrogate fuel, an interface between fluid dynamics and chemical kinetics codes must be used. A mesh independent study must be followed to validate results obtained from numerical simulations against the experimental data. To obtain comprehensive results, a detailed study should be performed for all ranges of equivalence ratios as well as stoichiometric condition. This gives rise to the development of a reduced mechanism that has the capability to validate engine performance parameters from stoichiometric to rich mixtures in a spark ignition engine. The above-mentioned detailed methodology was developed and implemented in the present study for premixed and direct injection spark ignition engines which resulted in a single reduced reaction mechanism that validated the engine performance parameters for both engine configurations.

**Keywords:** direct injection spark ignition (DISI) engines, premixed, CHEMKIN-KIVA, in-cylinder pressure, heat release rate (HRR), emissions
