PI: Ron Matthews, University of Texas.
The downsized, turbocharged, direct DISI engine is the most fuel efficient gasoline engine in production. Although not as efficient as a diesel engine, it is much less expensive and has superior performance. Thus, it is a very attractive option for consumers. LEVIII/Tier 3 emissions regulations will require automotive OEM fleet averages to be at SULEV30/Tier3Bin30 by 2025. That means emissions equivalent to the cleanest engines in production today regardless of displacement. Assuming the engine exhaust system is designed such that the catalyst is operational by 20 seconds into the emissions test cycle, the engine start and catalyst warming period become the prime contributors to cycle tailpipe emissions. Excessive hydrocarbon emissions are the main obstacle but meeting NMHC+NOx<30 mg/mi and PM<1 mg/mi are also challenging. Previously, Cheng et al. (1993) summarized the in-cylinder hydrocarbon emissions mechanisms with associated weightings for a warm, port fuel injected SI engine. Increased understanding of the mechanism weighting for a cold, modern, direct-injection SI engine is needed.