Extensive efforts are being made to improve emissions from 2-stroke diesel engines. These improvements are primarily directed towards older model year engines with relatively high emissions compared with modern diesel engines. While most researchers focus their attention on engine design changes that promise substantial emission improvements, this work dealt with the turbocharger characteristics, especially as related to using internal coatings on both the compressor and turbine housings.Two identical turbochargers were tested on a Detroit Diesel 6V-92TA engine. One of the two turbochargers was left in its production configuration while the other was coated with a clearance control coating on the inside of the compressor and turbine housings. This coating led to a significant reduction in the tip clearance of both the compressor and turbine wheels. Testing was conducted at steady-state as well as transient conditions, to evaluate the effect of this coating on performance and emission characteristics of the test engine. An oxidation catalyst was also tested in conjunction with both turbochargers. Results of this work are presented in this paper, and show the superior performance of the coated turbocharger.