Real World Operation of a Standard Lawn Mower Engine from a Scientific Perspective

This paper introduces a research project on a spark ignition engine used in non-road applications. The aim is to illustrate the present situation as basis for comparison and to identify possible improvement potential in terms of performance, efficiency or exhaust and noise emissions.

The study is carried out in two steps. First a standard walk-behind lawn mower is equipped with measuring instrumentation for recording the cutting forces and the engine variables during real world operation. The tests are carried out on three different lawn types and two different blade types are investigated. Consequently, in a second step the engine is analysed on the engine test bench in stationary and transient operating mode. A complete engine mapping is done regarding all relevant variables. Additionally to the outdoor tests, fuel consumption and engine out emissions are measured on the engine dynamometer. The recorded data enables a detailed analysis of the engine behaviour. Furthermore the load spectrum during real world operation is diagrammed and the most frequent load and speed points of the engine on the different lawn types are identified. Moreover the flyweight governor system and, closely connected with it, the carburettor behaviour of the engine is observed under transient conditions.