…Technologies for reducing evaporative emissions generated from gasoline vapors have been developed. To reduce evaporative emissions, both permeation from fuel and vapor lines and breakthrough from the evaporative canister need to be diminished. Fewer fuel line connections are used and hose and valve materials have been modified to reduce permeation. Component test results confirm that permeation is substantially reduced from the level of previous parts. A new type of activated charcoal, which has a high specific heat characteristic and improves adsorption and desorption performance, has been applied to reduce canister breakthrough. Additionally, the amount of purge air has been increased by applying purge control using an air-fuel ratio sensor. The problem of canister breakthrough has thus been resolved by the new evaporative canister combined with increased purge flow to the engine.
Endurance mode tests equivalent to 15 years/150,000 miles of driving were conducted on the fuel evaporative system parts and the results confirmed that this level of emission durability could be assured. The new system has been developed for the Sentra CA sold in the U.S. market. This vehicle satisfies the zero evaporative emission regulations as a result of adopting this combination of new technologies.