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A new simple ULEV system has been developed, using only an underfloor catalytic converter. The new system features a VTEC (variable valve timing and lift mechanism) engine with a newly developed catalyst, a precise air-fuel ratio control for maximizing the catalyst performance and the newly developed low heat capacity exhaust system with the air-gap. These technology have contributed to a reduction in the feed gas, the quick activation of the catalyst and an improvement in the maximum conversion ratio of the catalyst, making it possible to pass the ULEV standard without sacrificing vehicle output power.

ZLEV was accomplished by applying the Three-Stage Emission Management System, utilizing ultra-precise combustion and exhaust gas conversion control technology, and dividing the operation into three-stages of just after engine start, the warm-up stage, and normal running. These individual component technologies include improving engine combustion (high swirl combustion by variable valve timing and lift) and performing fuel control optimization during engine startup to reduce unburned HC emission, quick catalyst activation (engine control and catalyst improvements), HC adsorption of a hybrid catalyst (catalyst improvement and desorption conversion control), and high precision air-fuel ratio feed back control (catalyst condition predictive control, and others).