ESC, ETC and WHTC cycle emission tests were carried out on the engine test bench. The ammonia emissions of 10 heavyduty engines at the exit of catalyst were measured through the tunable diode laser gas analyzer. The results show that the gas engines running with the theoretical airfuel ratio produce the ammonia emissions in WHTC cycle when the lightoff temperature of threeway catalytic converter is available. The suburb condition marked with high speed and rich fuel characteristics is helpful to the formation of ammonia emissions.For diesel engine with SCR, the ammonia and NOx emissions are mutually inverse and the ammonia emissions are far lower than NOx emissions. The ammonia emission from diesel engine in cold WHTC cycle is lower than that in hot conditions. The peak of ammonia emission appears in the suburb conditions.
