Introduction: Ignition timing, in a spark ignition engine, is the process of setting the time that an ignition will occur in the combustion chamber (during the compression stroke) relative to piston position and crankshaft angular velocity. Setting the correct ignition timing is crucial in the performance and exhaust emissions of an engine.The objective of the present work is to evaluate whether variable ignition timing can be effect on exhaust emission and engine performance of an SI engine. Method: For achieving this goal, at a speed of 3400 rpm, the ignition timing has been changed in the range of 41° BTDC to 10° ATDC and for optimize operation, ignition timing has been designed at wide-open throttle and at last, the performance characteristics such as power, torque, BMEP, volumetric efficiency and emissions are obtained and discussed. Results: The results show optimal power and torque is achieved at 31°CA before top dead centre and volumetric efficiency, BMEP have increased with rising ignition timing. O2, CO2, CO has been almost constant, but HC with advance of ignition timing increased and the lowest amount NOx is obtained at 10 BTDC. Conclusions: In conclusion, it obtained that ignition timing can be used as an alternative way for predicting the performance of internal combustion engines. Also engine speed and throttle position were all found to significantly influence performance in this engine.

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