The intake system of a 2-Valve TJ376QE gasoline engine was modified so that its intake swirl and tumble motions were considerably intensified. The stronger air motions are helpful to organize air and fuel mixture strength distribution. The previous port electronic fuel injection system was modified and the technique of TEFI (Twice Electronic Fuel Injection per cycle) is employed. Through regulations of the two injection timings and proportions, an adequate air and fuel mixture stratification–quasi-homogenous mixture was produced and the lean burn can be realized in a product 2-valve S.I. engine. The experimental results show that the scope of bsfc reduction can be >10 % at quite wide load range by ether 1 injection or by 2 injections. Comparing to the conventional single injection, a leaner mixture can be used by TEFI and an even more reduced fuel consumption of 5% was reached by 2 injections. The optimized values of A/F ratio can be higher by 2–3 units of A/F than that of the single injection method. The TEFI can reduce NOx emission by 35–50% than that of single injection at engine load (bmep) range of 0.20–0.75 (MPa).

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