ABSTRACT
The need to improve the performance characteristics of the gasoline engine has necessitated the present research. Increasing the compression ratio below detonating values to improve on the performance is an option. The compression ratio is a factor that influences the performance characteristics of internal combustion engines. This work is a an experimental and theoretical investigation of the influence of the compression ratio on the brake power, brake thermal efficiency, brake mean effective pressure and specific fuel consumption of aRicardo variable compression ratio spark ignition engine. A range of compression ratios of 5, 6, 7, 8 and 9, and engine speeds of1100 to 1600rpm, in increments of 100rpm, were utilised. The results showsthat as the compression ratio increases, the actual fuel consumption decreasesaveragely by 7.75%, brake thermal efficiency improves by 8.49 % and brake power also improves by 1.34%. The optimum compression ratio corresponding to maximum brake power, brake thermal efficiency, brake mean effective pressure and lowest specific fuel consumption is 9.The theoretical values were compared with experimental values. The grand averages of the percentage errorsbetween the theoretical and experimental valuesfor all the parameters were evaluated. The small values of the percentage errors between the theoretical and experimental values show that there is agreement between the theoretical and experimental performance characteristics of the engine.