Application of an Electronic Fuel Injection System to a Single Cylinder, Four Stroke Engine

Abstract

One of the primary goals for any racing engine builder is to extract the maximum amount of power possible from a given engine size. Achieving this goal is as valuable for multiple cylinder, 500 or more cubic inch displacement automobile racing engines as it is for single cylinder, small displacement go-cart racing engines. Fuel injection systems have been manufactured that substantially increase the torque and power output of multiple cylinder engines. An electronic fuel injection system was developed for a Briggs & Stratton single cylinder gasoline engine that is similar to the type of engine used in most go-cart racing divisions. The engine was mounted to a dynamometer and the maximum wide open throttle torque and power values were measured for the engine in the original carbureted configuration. A different style carburetor with a variable air/fuel ratio was also tested. The engine was then tested for maximum wide open throttle torque and power values with the electronic fuel injection system installed. The first fuel injection tests were with a fixed injector pulse width and an open loop control strategy. A closed loop strategy was then developed and tested under a variety of fuel injection timing settings and lambda sensor target values. Fuel injection resulted in torque and horsepower improvements at all engine speeds, with approximately 20% torque and horsepower increase at top engine test speed.