Throttle Body Deposits - The CRC Carburetor Cleanliness Test Procedure

A nine-year effort from 1972 to 1981 was undertaken by the Coordinating Research Council Carburetor Test Procedure Panel to develop a laboratory engine test method for evaluating the effects of gasolines on the formation of throttle body deposits. This paper summarizes the test development, discusses effects of engine operating conditions on test severity, gives data on fuel effects, and presents a final test procedure that uses a removable carburetor throttle bore sleeve to permit weighing of deposits. A carburetor visual rating procedure was also developed. The final engine test procedure has proved to be an effective in-house tool for screening fuels and additives. An unresolved problem is poor interlaboratory reproducibility.