Characteristics of 2-Stroke Motorcycle Exhaust HC Emission and Effects of Air-Fuel Ratio and Ignition Timing

This paper discusses the results of studies of the exhaust HC emission of 2-stroke engines for motorcycles.

The major factor producing HC emissions from 2-stroke engines is the short circuiting of fresh charge. Therefore, we made a study of the relation between the delivery ratio and the trapping efficiency by comparing the test results and the theoretical values of perfect mixing. We then verified the effects of engine speeds and irregular combustion to the trapping efficiency.

Tests were conducted to clarify the relationship between the air/fuel ratio and HC concentration and mass HC emission, and the test results were compared with the theoretical values. In addition, a study was made on how to reduce the mass HC emission by optimizing air/fuel ratio.

Next, we launched tests to study the effects of ignition timing on HC emissions as well as the ignition timing characteristics and throttle opening and engine speed.