Future exhaust emission legislation for small engines, used on motorcycles and leisure products, will make it necessary for small engine manufacturers to follow the same path in engine development as car manufacturers have done. Using the approach of converting an automotive system to a one-cylinder motorcycle engine application will result in severe disadvantages due to the large differences in physical behaviour between the engine types.
In the paper here presented, an Engine Management System, SEM Direct, was developed with the demands of extreme applications like motocross, enduro, and off-road in the forefront.
A solution to the pressure detection problem has been developed, and has been shown to accurately predict engine load.
An adaptive function of the throttle position signal was developed to keep the throttle signal correct at small opening areas.
Immediate response control has been achieved by a combination of throttle detection, fast inlet pressure up date, and an advanced fuel injection strategy.
A one cylinder engine's sensitivity to wall wetting effects problem is solved by using a dual injection strategy together with an advanced fuel film compensation algorithm.
The results is an engine control system for one and two cylinder engines used in high demanding applications, that is able to combine response, low emissions and driveability.
The max engine performance can be improved by a higher freedom in inlet tuning design.