Development of an Injection System for Small Engines with Adaptive Control for Sensorless Lambda Operation 2019-32-0535

With increasing requirements for small engines in terms of functionalities and emission standards, it is essential to be able to offer an integrated full-featured injection system that will meet future requirements. The system described is particularly suitable for small to medium-sized combustion engines, such as power generators, lawnmowers and small motorcycles, and has a corresponding cost structure, compactness and a high degree of integration. The main subject of the development is an electronic fuel injection system, which can provide information about the current air-fuel mixture through model-based software algorithms and also has an integrated ignition coil.

This article describes the procedure and the status of the research results of this development project. The basis of the method as already known from similar approaches of stimulating the running engine by a defined feedforward control of the injection quantity. The engine response is analyzed by the developed algorithm and conclusions about the actual air-fuel ratio are drawn. Thus, without the need for a hardware sensor, an engine operation in the application-specific lambda range can be realized. The studies have been performed with a mechanical and an electronic speed governor, as well as different moment of inertia of the flywheel in terms of function, accuracy and required time on a single-cylinder 4-stroke gasoline engine.