Jack D. Benson

The Effects of Fuel Composition and Additives on Multiport Fuel Injector Deposits

A vehicle test program has been conducted to determine the effects of certain aspects of fuel composition and detergent additives on the for mation of deposits in multiport fuel injectors (UPFI). Eight identical vehicles were tested on programmed mileage accumulation dynamometers using a repetitive short-trip/hot-soak driving cycle and a base fuel with which deposits were produced. As part of the program, the base fuel composition was changed, and a variety of deter gent additives were tested in the base fuel. UPFI deposits increased with increasing olefin (particularly diolefin) content of the fuel, were unaffected by aromatic content of the fuel, and were not appreciably affected by the addition of alcohol. Also, several commercial detergent additives now available delayed or prevented deposit formation in port fuel injec tors. Oil companies have been strongly encour aged to use these or similarly effective addi tives to improve the quality of all grades of gasoline and ensure compatibility with present and future fuel metering systems.

COLD WEATHER FUEL REQUIREMENTS OF OLDSMOBILE DIESELS

Two Oldsmobiles with 5.7 L diesel engines and one with a 4.3 L diesel engine were tested to determine the effect of the low temperature properties of diesel fuel on operability (cold-start and warm-up driverability). Startability limits ranged from -18 degrees C to -24 degrees C and were unaffected by cetane quality of the fuel within the range of 39 to 50 cetane numbers. With untreated fuels, the cars would not operate when the fuel temperature fell below the cloud point of the fuel because wax crystals precipitated from the fuel and plugged the fuel tank filter. Low temperature operability was extended as much as 10 degrees C by the use of fuel flow improver additives and a modified vehicle fuel systems.

A Vehicle Test Technique for Studying Port Fuel Injector Deposits - A Coordinating Research Council Program

In late 1984 and early 1985, car owners in the Denver, Colorado area begain complaining about driveability. All affected cars had port fuel injection systems. With time, complaints with certain makes of engines spread to other geographical areas. A test method was needed to study the factors causing flow-restricting deposits in the injectors. The Coordinating Research Council Automotive Fuel Injector Deposit Group was organized in March 1986. A Test Procedures Subgroup was assigned the task of selecting a vehicle test procedure that related to field experience. This paper describes the CRC program to explore repeatability and reproducibility of the method.

Simultaneous Measurements of Driveability and Emissions at Cool Ambient Temperatures

Simultaneous measurements of cold-start/warm-up driveability and tailpipe emissions on a chassis dynamometer were made at 5{degree}C using four late-model vehicles. Two fuels were used: a low driveability index (DI) fuel containing 11% MTBE and 29% aromatics, and a high DI fuel with no MTBE and 43% aromatics. Tailpipe hydrocarbon emissions and total weighted driveability demerits (TWDs) both correlated with the fuel used; both increased significantly when high-DI/no-MTBE fuel was used. A strong linear relation exists between TWDs and simultaneously measured tailpipe hydrocarbon emissions. CO and NOx emissions did not correlate with fuel composition. 10 refs., 10 figs., 4 tabs.