1987-11-01

Intake Valve Deposits — Fuel Detergency Requirements Revisited 872117

BMW has undertaken a comprehensive program including laboratory simulation rig tests, engine dynamometer and fleet evaluations to evaluate the influence of mechanical and fuel variables on induction system deposits in modern port fuel injected (PFI) spark ignition engines. The primary focus of the program has been the deposit buildup on intake valves (IVD) and associated driveability impacts. Initial investigations of engine modifications yielded only marginal improvements relative to deposit build-up and, therefore this led to investigations of the effect of gasolines and additives.Fuel quality, type, quantity of additives and alcohol content have all been found to be major contributing factors to intake valve deposition. In addition, intake valve deposit weight has been directly related to warm-up phase driveability concerns using a newly developed driveability procedure. Unlike the CRC driveability of a broad spectrum of driving conditions, the BMW procedure specifically evaluates the driveability during the critical early warm-up phase.Using the previous information as a basis, further efforts were conducted to evaluate 6 commercial gasolines advertised as having various detergent additives. This was done to determine what, if any, influence these fuel/additive combinations had on intake valve deposition. Some of these combinations controlled intake valve deposits well, while others appear to contribute to intake valve deposits.

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