Effects of Combustion Chamber Deposits on Tailpipe Emissions

An initial investigation into the effects of combustion chamber deposits (CCD) on tailpipe exhaust emissions has been completed. Four different model vehicles were evaluated for tailpipe emissions at four different deposit conditions. The deposit levels included a baseline clean level, a condition after deposit accumulation, a condition after CCD removal and finally a reevaluation after disassembly and mechanical clean up of the entire intake system. A special rig was developed using a walnut shell blasting device to allow cleaning of CCD without disturbing other engine deposits and without disassembly of the engine. This approach was taken to eliminate numerous time related variables and focus on the effects of CCD removal. The results of this investigation confirm that directionally HC, CO, and Nox all increased after the deposit accumulation period and decreased with the removal of CCD. However, statistically only Nox emissions increased significantly at the 90% confidence level.