Cost reduction of engine management systems (EMS) for two-wheeler applications is the key to utilize their potentials compared to carburetor bikes regarding emissions, fuel economy and system robustness. In order to reduce the costs of a system with port fuel injection (PFI) Bosch is developing an EMS without a manifold air pressure (MAP) sensor. The pressure sensor is usually used to compensate for different influences on the air mass, which cannot be detected via the throttle position sensor (TPS) and mean engine speed. Such influences are different leakage rates of the throttle body and changing ambient conditions like air pressure.
Bosch has shown in the past that a virtual sensor relying on model based evaluation of engine speed can be used for a detection of leakage air mass in idling to improve the pre-control of the air-fuel ratio. This provides a functionality which so far was only possible with an intake pressure sensor. In this paper the air mass calculated from the model based engine speed evaluation is used to adapt the influence of ambient pressure changes e.g. because of different altitudes.
Furthermore, the usability of the engine speed based air mass for the realization of a limp home mode in case of a malfunction of the throttle position sensor is evaluated. Therefore, a demonstrator bike is equipped with an additional switch to bring in certain TPS errors which will be detected by the EMS.
