Impact of Exhaust Valve Leakage on Engine-Out Hydrocarbons

This study evaluated the contribution of exhaust valve leakage to exhaust hydrocarbon (HC) emissions. A simple procedure was instituted to measure exhaust valve leakage rates under static, prescribed conditions. This standardized leakage rate was experimentally related to the actual increase in exhaust HC emissions. An analytical model of exhaust valve leakage was developed to complement the experimental effort.