The Effects of Venezuelan Engines on Two Fuel Injection Technologies 942411

In 1986 the fuel injection systems began to appear on the Venezuelan vehicle market. Many foreign papers reported driveability problems when the injectors reached 10 % of flow restriction because of deposit formation in some vehicles equipped with electronic fuel injection systems. In fact, numerous Venezuelan drivers have complained about some engine problems that they have linked to injector plugging. Many of them have associated the plugging to Venezuelan gasolines. A fleet test was conducted in order to evaluate the effects of using Venezuelan gasolines on injection technologies representative of the country vehicle population. Six vehicles, divided in two groups, according to the injection technology, were tested in field and with dynamometer. Two different technologies were evaluated, a continuous fuel injection system and an electronic multi-port fuel injection system. The vehicles equipped with the electronic system had six-cylinder 3.1 1 engine, and the vehicles equipped with continuous fuel injection system had four-cylinder 1.6 1 engine. The dynamometer test included 300 short trip/hot soak (15/45) driving cycles. The first field test consisted in a programmed accumulation of 20,000 Km. A controlled commercial gasoline of the Venezuelan market was used because it was considered critical by its olefin content. A second field tests was performed to evaluate the effects of the gasolines purchased in service stations. This test consisted in programmed accumulation of 10.000 Km on the three vehicles which had electronic fuel injection system.

A laboratory bench injector tester was constructed for determining the fuel flow restriction during the tests. This tester allows the evaluation of both electronic and continuous injectors. Test precision was about 1%. Two types of flow tests were made on electronic fuel injectors. The first one, called static test, had the injector valve open during 8 seconds. The second one, called dynamic test, had the valve open and close during 10 seconds with a 50 Hz frequency. Continuous injectors were tested allowing to flow the injector during 10 seconds. Injector's fuel flow was measured every 2,500 Km (during the field tests) and every 50 cycles in the chassis test. Fifteen replicas of fuel flow measurements were made for each injector. The fail criteria for electronic fuel injectors was 10 % of fuel flow restriction.

Exhaust emissions (grams/kilometer of HC, CO, CO₂, and NOx ) and fuel economy (kilometer/liter) were also measured in the 20,000 Km test. The exhaust emissions were determined every 2,500 Km for vehicles equipped with continuous fuel injection systems taking seven replicas and every 5,000 Km taking only four replicas for those equipped with electronic fuel injection system. The exhaust emission were determined in a Clayton dynamometer chassis using a constant volume sampler (C.V.S) to take the samples. The EPA urban driving cycle was used as driving schedule.

None of the evaluated injectors presented plugging during these tests. Neither driveability nor any other kind of problems related to fuel injection systems were found; neither increase in the emission levels nor decrease in fuel economy were observed. Only one electronic injector presented flow restriction greater than 5%. In all those electronic injectors where flow restriction was found in both flow tests (static and dynamic), the flow restrictions in dynamic tests were always greater than those found in the other tests.