Development of PZEV Exhaust Emission Control System 2003-01-0817
A new exhaust emission control system has been developed which complies with the world's most severe emission standard: CARB PZEV. Leaner combustion in cold condition was enabled and rapid warm-up of a close-coupled catalyst was realized by utilizing a newly developed Intake Air Control Valve (IACV) system and hyper-atomization fuel injector. In addition, the newly developed HC adsorbing type 3-way catalyst realized cold HC reduction at lower cost.
For further reduction of the exhaust emission, the Variable Valve Timing-Intelligent (VVT-i) system was positively operated immediately after the cold start. By the suitable operation of Variable Valve Timing (VVT), the blow-back from the cylinder enhanced the fuel atomization and re-burning of remaining unburned hydrocarbons (HCs), and increased in-cylinder residual gas reduces NOx. In addition, to pursue a better catalyst conversion rate after warm-up, the oxygen (O2) sensor downstream of the close-coupled catalyst was improved to a new type. We have thus developed an exhaust emission control system with less emission variability to comply with the 15 years or 150k miles warranty.
TOYOTA Motor Corporation, DENSO Corporation
SAE 2003 World Congress & Exhibition
Advanced Catalysts for Emission Controls-SP-1756, Advanced Three-way Catalysts-PT-123, Advanced Developments in Ultra-Clean Gasoline-Powered Vehicles-PT-104, Emission Control and Fuel Economy for Port and Direct Injected SI Engines-PT-91, SAE 2003 Transactions Journal of Fuels and Lubricants-V112-4