الفهرس 
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Abstract
The experiments of this study were conducted on a four-cylinder, four-stroke, gasoline engine to study the effect of torque, catalytic converter position, ignition timing, and engine speed on the unburned hydrocarbon emissions and on other various performance parameters. The range of speed investigated was 1500- 3000rpm for a torque range of 5-63 N.m. Ignition timing was varied from l0 BTDC to TDC. Two positions of catalytic converter were investigated, one meter and two meters downstream of the exhaust manifold.
The present study shows that the hydrocarbon emissions from a spark ignition engine decrease when using a three- way catalytic converter placed two meters downstream of the exhaust pipe, ignition timing retardation, and increasing engine speed. While the hydrocarbon emissions increase as the torque increases and decreases again with a peak at the torque about 30N.m.
The study also shows that the volumetric efficiency increases with ignition timing retardation, and increases of torque, while the volumetnc efficiency decreases with engine speed increases. The specific fuel consumption decreases with increases of torque and increases with ignition time retardation, and when the three-way catalytic converter is located further downstream the exhaust pipe.