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A discriminating dynamometer-based test was developed for evaluating cold start and warmup engine performance based on in-cylinder pressure measurements. The dynamometer test offers advantages in time required, flexibility and reduced variability over the vehicle procedure on which it was based. A parametric study on fuel driveability index (DI), ethanol content and intake valve deposit (IVD) rating demonstrated that each of these parameters had a statistically significant impact on engine cold start performance. Simple numerical offsets to fitted models based on oxygen content of the fuel did not account for the difference in engine performance of hydrocarbon-only versus ethanol-containing fuels. The effect of IVD on engine performance did not appear to depend on the DI of the fuel. The benefits of cleaner valves are seen even in fuels of very low DI.

This work presents a follow-up to previous efforts by the authors to investigate the susceptibility of gasoline direct injection (g-di) engines to deposit formation and the effect of those deposits on vehicle performance. A series of injector keep clean and clean up tests in base and additized fuels utilizing the ASTM D 5598 cycle provided a range of injector fouling levels. It is found that the g-di engine employed here is more susceptible to injector deposits than even the sensitive port fuel injected (PFI) engine used as industry reference in the D 5598 procedure. Injector keep clean and clean up performance of several representative deposit control chemistries are evaluated. In order to determine the effect of injector fouling on performance, emissions and driveability tests are performed on the vehicles at varying levels of injector fouling. Regulated emissions, particulates, fuel consumption and driveability are all shown statistically to be linked to injector fouling.