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The wall-wetting dynamics represent a very important subsystem of the air/fuel path of an SI engine. The precise feedforward control of the air/fuel ratio requires a valid model of the wall-wetting dynamics over the whole operating region of the engine. A global wall-wetting model has been developed for a production SPFI gasoline engine. This model is capable of describing the wall-wetting dynamics not only in a fixed operating point, but also for radical changes of the operating point. Its structure specifically allows for model-based compensator design and on-line parameter identification. Earlier, related publications discussed linear model structures. Those models described the dynamics around a fixed operating point only. This paper shows how one global model for the whole operating range can be constructed from a linear model and its parameter range.

The need for a stoichiometric air-to-fuel ratio in an SI engine with a catalytic converter makes the accurate knowledge of the air and fuel paths indispensable. This investigation is focused on the prediction of the air mass flow into the cylinder without the use of an air mass flow meter. A dynamical mean value engine model of the intake manifold has been derived. Combining a gain-scheduling and a self-tuning algorithm has been found to be a good strategy for the persistent adaptation of the intake manifold model to the changing ambient conditions and actuator parameters such as aging or malfunctions. The adaptation algorithm is based on the direct identification of the air mass flows entering and leaving the intake manifold, thus the identified parameters can be interpreted as the throttle and the filling characteristics. The recursive least squares algorithm has been used for parameter identification.

In this paper the fuel path of a sequentially injected gasoline engine is discussed. Since a fraction of the injected fuel suffers a delay due to the wall-wetting phenomenon, in transient phases a significant deviation of the air-to-fuel ratio from its setpoint can arise. The amount of fuel on the manifold wall and its rate of evaporation cannot be measured directly. Therefore, the effects of the wall-wetting on exhaust lambda and engine torque have to be considered for the identification of the dynamics. The dynamics of the exhaust-gas-oxygen (EGO) sensor is not negligible for the interpretation of the lambda measurement. Since both the dynamics and the statics of a ZrO2 Sensor are very nonlinear, a normal EGO-sensor is not suitable for these investigations. On the other hand, the engine torque is a good measure for the cylinder lambda when all other effects which lead to torque changes can be eliminated.