This study presents the engine performance, fuel economy and exhaust emissions at variations of air intake pressure. In a carburetor system, the air intake pressure is influenced by the degree of opening throttle plate and the Venturi effect which draws the fuel to the combustion chamber. The experimental work was carried out on variations of engine speed and load using a single cylinder four stroke gasoline engine attached to a dynamometer. The measured exhaust emission compositions are used to determine the mode of combustion. The results show that the standard air intake system resulted in rich combustion which then led to incomplete combustion, which was caused by less availability of air for the combustion process. Eliminating the air filter reduces the air flow restriction in the air intake system resulting in better combustion and less unburned components due to higher air availability. Higher air intake pressure is better at increasing the efficiency of combustion within a limited time to improve fuel economy, power output and exhaust emissions. Better combustion also leads to reduced unburned components such as carbon (C), hydrogen (H 2 ), carbon monoxide (CO) and hydroxide (OH), which results in cleaner emissions.

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