A Test Procedure for Identifying the Gasoline's Deposit Formation Tendency on Intake Valves

Deposit formation on the intake valve of spark-ignition engines is a well known and old problem. The intake valve deposits work like a sponge and absorb the injected fuel during the acceleration, which leads to a leaner air/fuel ratio. Non-uniform running may occur during engine warm-up and acceleration periods. The poorer running behavior of the engine increases the emissions and shortens the life of catalytic-converter. An increase of fuel consumption would be followed.

A laboratory test procedure was developed and used to evaluate the liquid fuels tendencies to build deposits on the intake valves. This test method has shown a great accuracy and is very reliable. It can help accelerate development of additives. It can also be used as a pretest method for gasoline quality control. Chemical analysis and comparison between the results achieved by this method and the deposits from the intake valves show a great similarity of the substances found in the deposits.