Minimization of Inverse Inlet Flow and Consequent Reduction in Specific Fuel Consumption in Gasoline Engines

In this paper possible causes of inverse inlet flow observed in one-to four-cylinder gasoline engines are discussed. One possible cause is the angle between crank throws. This was checked experimentally on a four-cylinder engine operated as a two-cylinder and was found to have little effect. Inlet manifold resonance was then postulated as the most probable cause. Accordingly, an inlet manifold resonance analysis was made for a two-cylinder engine. As a result of this analysis changes were made in the inlet manifold. These changes, plus changes in the venturi, substantially reduced the visible inverse flow as well as reducing the brake specifice fuel consumption from 265 grams/psh to 216 grams/psh at 3000 rpm. In addition, better balance of load between the two cylinders was observed.