Development of PZEV Exhaust Emission Control System

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 (WT-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 (O 2 ) 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.