The feasibility of igniting lean air-fuel mixture with a torch formed by injecting a stoichiometric mixture over a hot surface near the end of the compression stroke is explored and proved.Several variables affecting the performance of the mixture injected surface-ignition engine were identified, and their effects on the engine operation were examined.Lean misfire limits for engine speeds between 2000 and 3000 RPM were found to vary between air-fuel ratios 19.7:1 and 21.6 for regular blend gasoline in a 4-cylinder configuration. Fuel consumption comparisons with a standard spark-ignited engine of equal displacement and compression ratio showed improvements for the MISI engine.Specific exhaust emissions of CO. HC. and NOx from both engines were compared. The MISI engine had generally the same levels of CO and HC. and higher levels of NOx emissions than the spark-ignited engine.