Study on manifold injection of LPG in two stroke SI engine

Gasoline and liquefied petroleum gas (LPG) were injected into the manifold of a 145 cc two stroke engine using a specially developed electronic circuit to have a close control over the air fuel ratio. Experiments were carried out at 3000 rev min-1 and fixed throttle positions of 10, 15, 25, 40, 50 and 100% of full opening. The amount of fuel injected (air fuel ratio), injection timing and injection pressure were varied. The maximum brake thermal efficiency with LPG was 25% and that with gasoline was 23%. The engine could generally operate with much leaner mixtures with LPG due to its good mixture formation capability. HC levels and exhaust gas temperature were slightly higher with LPG while NO levels were comparable. It was found that the injection pressure had to be reduced at part throttle conditions in order to get better engine stability and performance. The maximum power output with LPG was lesser than that with gasoline. © 2007 Energy Institute.