The diesel engine can be an effective solution to meet future greenhouse gas and fuel economy standards, especially for larger segment vehicles. However, a key challenge facing the diesel is the upcoming LEV III and Tier 3 emission standards which will require significant reductions in hydrocarbon (HC) and oxides of nitrogen (NOx) emissions. The challenge stems from the fact that diesel exhaust temperatures are much lower than gasoline engines, so the time required to achieve effective emissions control after a cold-start with typical aftertreatment devices is considerably longer.
To address this challenge, a novel diesel cold-start emission control strategy was investigated on a 2L class diesel engine. This strategy combines several technologies to reduce tailpipe HC and NOx emissions before the start of the second hill of the FTP75. The technologies include both engine tuning and aftertreatment changes. The benefits of the engine tuning changes were presented in detail in a previous publication. This paper expands the discussion to include test results obtained with the modified aftertreatment device: namely, a close-coupled LNT with a low-temperature formulation.
Using this strategy, effective NOx and HC control was achieved within 50 seconds after the start of the FTP75. Compared to a production Tier 2 Bin 5 diesel vehicle, a 57% reduction in cumulative tailpipe NOx + HC emissions was obtained after the first hill of the FTP75. This level of cold-start emission reduction along with modern NOx aftertreatment performance during hot operation confirms that this strategy is a viable LEV III option.
