Brief History of Fuel Injection
Although Chevrolet fuel injection had been around as early as 1957, the progress leading up to it began as early as 1883 with Edward Butler, Duetz and other pioneers. It wasn't until World War II when Germany pursued it further by bringing the Robert Bosch company into developing fuel injection for the aviation field. During that time, however, Great Britain and the United States combined efforts to build a system to use in the Patton tank.
Electronic fuel injection had its beginnings in Italy by a engineer named Ottavio Fuscaldo incorporated an electrical solenoid as a means to control fuel flow, this was a modern electronic fuel injection development.
After the war, most aircraft industries turned away from further development and towards jet engines, fuel injection was basically put on the back burner. Even the automotive manufacturers were content to make minor progressive developments to the inexpensive carburetor.
Then in 1949 an Indy race featured a fuel injected Offenhauser. The system was developed by Stuart Hillborn and featured an indirect injection system.
Later Chevrolet introduced the Rochester Ramjet in 1957. It was also used in the 1957 Pontiac Bonneville, it used a lot of systems designed by Hillborn. The system was not popular with the general public and it was dropped after 1959, except for the Corvette which used it as an option until 1965. Across in Europe, some manufacturers, including Bosch pursued fuel injection on Volkswagen, Mercedes Benz in the 60's and 70's.
GM then in 1975 introduced the first mass produced domestic fuel injection system on the 1976 model Cadillac Seville. It was a system consisting of a throttle body, 8 fuel injectors mounted on a fuel rail directing fuel into the intake, a crude analog computer and various sensors. It had been developed between Bendix, Bosch and General Motors. It was at that time that it was necessary for the industry to developed specialized troubleshooting techniques and flow charts which are now taken for granted.
A ecm from a 1978 Cadillac Seville, this was a rudimentary analog computer at best. Note the baro "MAP" sensor with vacuum line on the circuit board (center picture). Last picture shows close up of the early integrated chips (IC's).
Later in 1980 the first digital computerized control was introduced for Cadillac called Digital Fuel injection (DFI), originally conceptualized as a multipoint injection, cost constraints again limited it as a throttle body system with two fuel injectors. The introduction of a digitally controlled system made it possible for a finer refinement of fuel control via various sensors, and to make minor adjustments on the fly and to be able to store trouble codes indicating malfunctions that can be recalled by a technician in troubleshooting.
In 1982, Pontiac introduced the single injector throttle body system on its 2.5L 4 cylinder "iron duke" engine. Chevrolet and other divisions introduced it on it's "A" and "X" body designs including Citation, Celebrity, Skylark, Omega, Phoenix and even on the Camaro.
1983 saw the introduction of the cross fire injection on the 5.0L Camaro/Firebird and the 5.7L Corvette. This system had two single throttle bodies mounted on opposite ends of a special manifold and allowed for better fuel atomization and velocity. It was good for a 20 hp gain over a carbureted 5.0L Camaro. The system was not perfect, and suffered from some of the same problems as its carbureted cousin such as manifold wetting and poor fuel distribution, and special problems such as icing of the throttle body bores under certain conditions, and a leaky air intake seal. Fortunately, the system was short lived as GM's engineers worked overtime on their next project and they would be greatly rewarded for.
A technological milestone was reached in 1985 with the introduction of the Multiport Fuel Injection on its 2.8L V6 used in the Celebrity, Camaro, Cavalier, Citation and a multitude of other GM division vehicles. Also in the same year Chevrolet introduced the Tuned Port Fuel Injection on the 5.0L Camaro and the 5.7L Corvette. Compared to the cross fire, with various valve train improvements was good for a 40 hp gain on the 5.7L engine! The system with its specially designed intake, elegant long runners and tightly controlled fuel management was good for powerful low end torque and mid range power.
Why is it called Tuned Port: The term "tuned port" has to do with taking advantage of the engines particular volumetric efficiency. By sizing the length and diameter of the intake runners to the resonance or "pulse" of intake valve opening, the flow can move uninterrupted with little or no interference, this helps fill the cylinders more efficiently. Long runners are good for tremendous low end torque and mid-range power, while short runners, like those on LT1 and LT4 power plants, promote higher overall power, but lose some torque at lower rpm's. Unlike the carburetor or tbi manifold which must handle wet mixture, the tpi manifold only has to handle air, thus allowing for a more flexible design in the manifold. The carburetor/tbi manifold has uneven runners, allowing for uneven distribution of the fuel charge, the tpi manifold is designed with all runners being of equal length and the fuel being injected just ahead of the intake valve, it is no wonder the tpi system is powerful, yet fuel efficient.
There has been minor changes over the years. The 1985 system is a one year only, as it has a separate "piggyback" mass air flow (MAF) control module on the ecm, and a one year only ecm, #1226870. It will not electrically interchange with the 1986-89 harness. In 1989, however the cold start injector was eliminated. In 1990, The mass air flow was eliminated and speed density control was introduced. It required a different harness and computer. This system was used all the way up 1992, where it was replaced by the shorter runner designed LT1 and LT4 power plants.
Although these later engines produce more stock horsepower, the 85-92 TPI system is superior in low end power and torque.
So don't give up your TPI plans, the aftermarket is loaded with performance parts that will make your tpi equal or better than the LT1 and LT4 based engines. Lets get started!
My 1978 Camaro 350 TPI Aug.2000.
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