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Air-fuel ratio (AFR) is a crucial parameter for combustion controls in internal combustion engines. An incorrect AFR metering for reciprocating internal combustion engine causes high toxic gases emissions formulation, serious fuel consumption problems and unbearable combustion noise and combustion deterioration. Traditionally, the AFR is obtained by direct measurement of intake air and the fuel either injected into the combustion chamber or pre-mixed at the carburetor. However, the accurate AFR obtained from direct measurement is difficult due to measuring equipments resolution prone to errors. This paper describes a method for accurate determination of air-fuel ratio based on exhaust emission gas analysis as an additional tool used to be validated the conventional direct air fuel flow rates measurement.

This research work focuses on the unsteady heat transfer and temperature distribution over the engine cooling jackets. The efforts are gestated to generate the time-dependent effects of heat transfer from the combustion chamber to the cooling jacket of a 4-cylinder 1.6-L cam-profile switching system SI engine. The characteristic behavior of heat transfer to the coolant at lower speed (idle speed/traffic signal) or when the engine is shut down after driving the vehicle for a significant period manifests unstable temperature rise with respect to time. It has been observed that the temperature of the coolant inside the jacket rises up within a very short period of time. It can be a case due to the shut off of the actuators (coolant pump, fan) which helps the cooling system to take effect according to the demand of the thermal efficiency of the engine.