抄録
The present study has been performed to elucidate the effect of engine operating conditions such as engine speed, charging efficiency, air-fuel ratio and ignition timing on the heat loss to the coolant in 4-cycle S. I. engine. It has been shown that the ratio of the heat loss through the cylinder head to the total heat loss is 65% and is independent of the operating conditions. The ratio of the total heat loss to the coolant to the heat supplied by fuel decreases as the engine speed increases or the charging efficiency increases. It is minimum when the ignition timing is MBT.
