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This paper presents a model-based design approach to feedback air-fuel ratio control for SI engines during fuel injection path changing. For the SI engines, emission performance during transient mode is remarkably influenced by air-fuel control, and to improve the efficiency of combustion engines, the fuel injection path is frequently changed from port-injection to direct injection or reverse. Therefore, how to describe the dynamics during the fuel path changes and to compensate the fuel injection are important issues to achieve good transient performance of air-fuel ratio. In this paper, a feedback control scheme with a mode changing command triggered feedforward compensation is proposed, and experimental validation on a six cylinders engine will be demonstrated.

1 Many environmental problems, such as global warming, drain of fuel and so on, are apprehended in all over the world today, and down-sizing is one of the wise ways to deal with these problems. It is significant that a decrease of the engine power must not be produced by using a small displacement engine, so more efficient engine system should be designed to increase the torque with a little fuel. This study achieves an improvement of efficiency for mounting the super charging system on the small displacement engine. As a result, comparing a super charged engine and a naturally aspirated one to drive the same course and laps, fuel consumptions are 2547 [cc] and 3880 [cc], respectively, and an improvement of fuel consumption is 52%. Designing points to mount super charging system is introduced below. 1 It can be forecasted that intake air blow-by gas at the combustion chamber is increased in low engine speed because engine for motor cycle is used.