Technical Paper
Small Engine Combustion Chamber Optimization Using an Ionization Probe Head Gasket
1994-09-01
941805
Small utility engines have been targeted with new exhaust emissions regulations by both the United States Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). CARB emissions standards are already in place, as shown in Table 1, while EPA is still considering legislation. Overhead valve (OHV) engines and those near the upper end of the power limit for small engines, 18.6 kW (25 horsepower), will be able to meet these new regulations much easier than the lower power engines and those of side valve design. Side valve, or L-head engines, have relatively higher emissions levels and will require a greater effort to meet regulations. One of the reasons that L-head engines produce higher levels of exhaust emissions is due to relatively high combustion chamber surface-to-volume ratios compared to OHV engine combustion chambers.