CRC Pilot Program to Investigate the Effect on Driveability of Intake Valve Deposits and Variations in Fuel Volatility

During the Coordinating Research Councils CRC program to select an engine to replace the BMW 318i as the industry standard intake valve deposit test engine, an opportunity was identified to compare the driveability performance of the engines evaluated with and without intake valve deposits. A pilot program was thus conducted by the CRC Volatility Group at Southwest Research Institute during late 1 991 and early 1 992 to investigate the relationship between intake valve deposits and cold-start and warmup driveability. Eight vehicles were tested using three fuels with varying T50 levels. Duplicate ratings were made using both the BMW Driveability Test Procedure and a modification of the CRC Cold-Start and Warmup Driveability Procedure. None of the three candidate engines were as good as the BMW 318i reference engine in discriminating valve deposit effects on driveability. Rater differences obscured other possible effects.