Study of Impact of Spark Timing and Compression Ratio on Performance of SI Engine

Abstract — The improvement of performance characteristics of gasoline engine study is needed as automobile series of development has been changing rapidly. This work enhanced the importance of design variables of I.C. engine for better performance with fewer emissions. The spark timing and compression ratio are the two important design variables to deal with for effective performance of engine. This paper presents the effects of spark timing and compression ratio on the performance of a four stroke single-cylinder spark ignition engine. The study evaluated results of research in the area of spark ignition engine and is assessed by studying its performance characteristics relative to find the optimum. Experiments were conducted at different ST of 200 to 300 BTDC and CR of 3.5 to 9. The results have shown that performance parameters: brake thermal efficiency and volumetric efficiency increased for advanced timing. Specific fuel consumption and exhaust gas temperature decreased with earlier timing before top dead centre. The peak pressure increases with increasing spark advance. The increased compression ratio results increased BTE and EGT increased and then decreased. BSFC decreased with increased compression ratio. The engine for tests used was variable compression ratio engine with adjustable dome head with wheel. The setup is running at constant speed of 3000rpm with water cooling system. The purpose of spark advance mechanism is to assure that under every condition of engine operation, ignition takes place at the most favourable instant in time. Increasing the compression ratio below detonating values to improve on the performance is another choice of variable