Honda ULEV and ZLEV systems

Its LEV (Low Emission Vehicles) requirement, roughly equals to Euro 2000, has been effective since 2000.

After 3 years, ULEV (Ultra Low Emission Vehicles) requirement restricted the pollution level to 30% of today's standard, that is similar to the Euro 5.

At the focus of attention is the so-called non-methane organic gases (NMOG). Organic hydrocarbon compounds such as aldehydes, alcohols, alkanes, aromatic compounds and esters found in car exhaust, and which experts consider to be responsible for the increase in the concentration of ozone in the atmosphere.

All car makers are required to ensure that the passenger cars which they sell in California do not exceed a certain annual NMOG fleet average.
Honda is currently leading LEV and ULEV technology.

Back in 1995, it created the first ULEV engine in the world and installed to Accord. Today, while other car makers are working hard on their ULEV engines, Honda once again lead this field by introducing an even cleaner ZLEV ( Zero Low Emission Vehicles ) engine.
Basically, ZLEV based on ULEV but improves the catalytic converter arrangement.

During start up, its VTEC system lifts one of the intake valves higher than the other Because of unbalance pressure, swirl will be created in the air, thus leads to better mixing of fuel and air. As a result, leaner fuel/air ratio (16 : 1, compare with conventional 14 : 1) can be achieved.
As usual, when the engine has started, the catalytic converter are still too cold to be effective.

Therefore a close-coupled high efficiency converter, locating just at the exhaust port, is employed for the benefit of faster heat up. Therefore a newly developed hydrocabonate-asbsorbing catalyst is used to absorb the HC temporarily. At the same time, another converter is pre-heating for later use.


Author: AL
Source: Autolatest & AZ