Abstract
The reduction of hydrocarbon (HC) emissions at fast idle is important to improve emission performance of the Gasoline Engines. HC emissions are caused by the deposition of fuel on the combustion chamber walls. In order to decrease fuel deposition, in-cylinder air flow is enhanced by causing high intake air velocity. High intake air velocity is achieved by using intake valves with variable valve system. Intake valve lift is set low and intake valve open timing is set after of the top dead center. Incorporating this technique is found to decrease HC emissions of Direct Fuel Injection Engines thereby improving combustion stability.
