Exhaust Purification With Small 2-Stroke Engines - A Challenge for Catalytic Systems

Two-stroke engines used in many different applications show comparatively high exhaust emissions, especially in hydrocarbons. In some countries they contribute considerably to the total HC emissions. Test methods and regulations to reduce these emissions have been discussed by European institutions for two-wheeled vehicles with small engines. They are shortly outlined.

Systematic investigations of emission patterns for HC, CO, NO_x and O₂, and temperature distributions over families of torque curves for a 50 cc. engine are presented.

The use of small, low cost catalytic systems to reduce these emissions is tested on stationary engines (conversions as function of engine modes) and on the roller dynamometer (emissions during the applicable ECE cycle) using commercial fuel (0.15 g Pb/l). The overall efficiency is mainly determined by oxygen concentrations and temperature.