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This paper gives a thorough review of the HC/CO emissions challenge and discusses the effects of different diesel oxidation catalyst designs in a pre turbine and post turbine position on steady state and transient turbo charger performance as well as on HC and CO tailpipe emissions, fuel economy and performance of modern Diesel engines. Results from engine dynamometer testing are presented. Both classical diffusive and advanced premixed Diesel combustion modes are investigated to understand the various effects of possible future engine calibration strategies.

Further tightened emission legislation and new engine technologies increase the requirements for the exhaust after-treatment system of modern diesel passenger cars. Especially the increasing raw emissions of HC and CO as well as the low temperature of the exhaust gas for a long period during cold start of the New European Driving Cycle (NEDC) require additional efforts in the design of the oxidation catalyst system [1]. A highly efficient micro catalyst, which is mounted in front of a turbocharger, can help to treat efficiently these high HC and CO emissions. Due to the higher temperature level in front of the turbine and the significantly increased mass and heat transfer by turbulent flow, efficiency especially during cold start is highly increased. However the packaging constraints are more critical in this area due to heat considerations and also to maintain engine performance.