A Series of tests were performed to decide the relationship between the air-fuel ratio and the composition of exhaust gases with a domestically made 1415cc SI engine and as a result a curve correlation A/F ratio with carbon mole percent of exhaust gas was obtained.
Using the relation, fuel distribution aspect of the 4-cylinder engine was investigated by means of the gas analysis for each cylinder together with a performance characteristics on powers and fuel economy.
Three kinds of mechanical devices designed for the improvement of fuel distribution were installed in the intake manifold and the resulting changes of fuel distributions as well as the engine performance were investigated.
It was found that the degree of maldistribution in terms of A/F ratio among 4 cylinders was deteriorated noticeably during WOT conditions and this could be improved considerably by extended riser and/or a strong turbulent flow induced by another device at engine speeds above 3500rpm.
However, it was observed that improvement in fuel distribution was accompanied with the reduction in maximum power to some extent in all cases. The reduction in output was caused by the decrease in intake air. It was also found that even the balanced distribution of A/F ratio did not improve the BSFC at rich mixture ratio, however, always resulted in the better BSFC at lean mixture ratio.
Based on these data, it was conceivable that in order to achieve a good power and fuel economy at the same time the air flow passage in intake manifold should be enlarged so that intake mixture might have less flow restriction while adding longer riser and/or other devices to induce more turbulence in flow.