THE IMPROVEMENT OF COMBUSTION PROCESS AND REDUCTION OF UNBURNED HYDROCARBON EMISSION IN A TWO-STROKE MOTORCYCLE*

Abstract

In desert areas in which there are few asphalt roads, heavy vehicles can not commute easily. Two-stroke motorcycles are lighter and have higher output power in comparison with similar four-stroke ones. In the present project, a two-stroke motorcycle that is used in Iran and is the most powerful has been improved. Its engine is cooled with air and its average fuel (premixed petrol and oil or pet-oil) consumption is 5 liters per hour. The timing ignition in the base engine is constant for all conditions. Then, the effect of the improvement parameter of ignition timing is carefully examined and automatically tuned in terms of engine speed. This modification has been achieved by using a mechanical tuning system based on the governor timing method. Finally, the major emission pollutants' parameters in modified and base engines are compared according to ECE regulation No.40. In this effort the following useful results are achieved: a) The fuel consumption has been reduced to 3.5 liters per hour. b) The UHC emission is reduced by 30 percent with the base engine. c) The movement acceleration from rest condition to 60 kilometers per hour has been remarkably ,m, increased in comparison with the base engine.