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ABSTRACTAs the LPG vehicles have lower emissions than the
gasoline vehicles, the LPG vehicles have the potential to
improve the metropolitan air pollution. In Taiwan, the
pollution problem of motorbikes is more serious than that of
automobiles. However, applications of LPG just are concentrated
on automobiles only. The research of LPG motorbikes has not
begun yet.This is a preliminary study on the LPG motorbike
engine. Two studies were conducted in this project. The first
one is to study the influence of engine design parameters and
the fuel system design parameters on the power and exhaust
emission of LPG motorbike engines. The LPG vaporizer
temperature, the air-fuel ratio, the spark ignition timing, and
the compression ratio were considered in this study. In the
second part of study, the performance as well as the emission
characteristics were compared with thResults of experiments show
that increasing the compression ratio can improve the engine
performance. However, the spark timing did not have significant
effect on engine performance. In changing the A/F, the engine
performance as well as the engine emissions were affected. As
for the effect of vaporizer temperature, no conclusive results
can be obtained.Results of measured data showed that the
unburned hydrocarbon is still very high for the LPG engine.
This is because the unburned HC is caused by the fuel short
circuit, which can not be eliminated by changing fuel to LPG.
Besides, the LPG engine output torque is 20-30﹪lower than that
of gasoline engine. There are two reasons for the deficiency of
engine torque. One is that the gaseous fuel would replace some
of the volume of air such that in inlet air flow rate is
reduced. The other reason is that the
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