1997-10-01

A Laboratory-Scale Test to Predict Intake Valve Deposits 972838

The performance of modern spark ignition engines with electronically controlled fuel injection systems may be adversely affected by formation of deposits around the intake valve. The rate of deposit formation is sensitive to fuel composition and boiling point distribution, as well as engine design and operating conditions. Deposit control additives are available, and full-scale engine and vehicle tests have been developed to rate fuel deposition characteristics. However, the expense associated with full-scale testing, combined with the many variables affecting repeatability, create a need for a well controlled laboratory-scale bench test. This paper describes the development of both the test apparatus and methodology to accurately reproduce the conditions present at the intake valve of an operating engine. Procedures were developed to simulate both a “keep clean” sequence, with neat or additized fuel, and also a “clean-up” sequence, using fuel that contains a deposit control additive. The results indicate that significant differences exist in the deposit forming characteristics of commercially available gasolines. The Intake Valve Deposit Apparatus (IVDA) provides good repeatability with a minimum of fuel. Most importantly, good correlation is obtained among the IVDA and both the BMW and Ford 2.3L IVD tests.

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