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                          CHEVROLET CROSS-FIRE INJECTION 1982-1984

                                                           Model 400 TBI

The Cross Fire Injection albeit as short lived as it was, was considered to be "cutting edge" when it was introduced in the fall of 1981 for the 1982 model years.  Although Camaro owners could opted out and get a higher output 5.0L with a 4 bbl carburetor, it itself was a late introduction (1983) so most did not know about it. Vast majority who checked off the V8 engine got the CFI system.  The 1982  Corvette owners did not have an option, they got the cross fire system though it was the 5.7L engine.  The 1982  5.0L engine was rated at 165 bhp, while the 5.7L came in at 200 bhp. In 1983 the 5.0L CFI was rated at 175 bhp, while the 5.0 4bbl  H.O. was rated at 195 hp. There were no Corvettes produced for 1983. However, while the Camaro dropped the CFI option for 1984, the new generation C5 Corvette had the 5.7L CFI for one more year, it was rated at 205 bhp. 

Funny, when you think about it and look at the performance figures, they are lame by today's standards. 

The engineering on this began in the late 1970's, when it was obvious that current emission standards were going to be tighten even more in the 1980's.  The goal was to develop a better fuel delivery that needed to be  less expensive than the  high pressure electronic fuel injection currently used on the Cadillac. The first TBI units developed strangely enough debuted on the 1980 Caddy as "Digital Fuel Injection" or DFI for short. These featured a low pressure pump, around 13 psi for the fuel delivery, and designed so that the vapor bubbles rose to the top of the injector, while fuel  was delivered to the bottom of the injector and sprayed in a fine mist. 

All the proceeding  throttle body injections systems for GM would be built around this designed until 1996, being replaced by the multiport injection Vortec system. These became a proven design for reliability and ease of maintenance.

The manifold itself, was a part of previous history.  The original Z28 that Roger Penske raced in 1968, featured dual Holley  4 bbl carburetors that sat over the valve covers. That manifold, with some minor mods, was adapted to accommodate the twin throttle bodies and the EGR valve. GM already had the money spent and the dies to cast the pieces. 

The ports on the intake were extremely small, about 2/3's the size of the port on the cylinder head. GM engineers said this was done to create more torque on the bottom end were the engine spends most of its life, but as  performance was factored in, they ran out of breath very quickly above 4K rpm.  There is a lot of stories of conspiracy to hold back the  performance potential purposely to make the newer TPI system more powerful.  You can make your own judgment.

The swirl vanes in each throttle body bore was to designed to evenly distributed the fuel.

Another area of concern was the cowl induction, which was prone to leakage if ever subjected to heavy water pressure. Though this was never completely solved, the  factory quick fix was to have several  5/16" diameter holes in the bottom lid to let the excess water escape.

They ran best for short bursts and as far as the reliability of the throttle bodies themselves, as long as no one tinkered with the very touchy linkage adjustments, were pretty good for the day. Regular maintenance was the key, keeping the air and fuel filters changed when due. One troublesome spot would be the Idle Air Control motors (IAC). If one got weak, it would surely cause a idle control problem, thus many inexperienced owners and  mechanics would try to adjust the throttle blade angles via the linkage and that's when the headaches would start. When one IAC went bad, it was best to replace them in pairs.

The ecm's for the day, were  only capable of 60 calculations per second and ran on a eprom chip containing the engine calibration data on 1K memory. Today's GM vehicles ecm (PCM)  exceed over 1 meg of code and capable of several thousands of calculations per second. 

But these little unassuming units filled the gap until the more sophisticated TPI (Tuned Port Injection) debuted in the fall of 1984 for the 1985 model years and ushered in the new era of the fuel injection performance.

                                              This unit is beautified. They never looked this good from the factory. The factory air cleaner was painted to be close to the original "wrinkle" paint design as possible.

Fuel Injector Replacement Numbers:

 GP=GP-Sorensen part numbers

The fuel injectors are specifically calibrated for each unit and must be installed in its respective throttle body unit. Due to the slight difference in fuel pressure drop across injectors. The fuel enters the left hand (drivers side) unit and then is delivered to the right side before being returned to the tank.  The right hand (front) unit contains the actually fuel pressure regulator, while the rear unit has an dampener-accumulator spring.

For clarification, the front unit is the right (passenger) side throttle body.

The engine control module or ECM was a simple design with a lot of discrete components (individual resistors and capacitors) on board.  As primitive as it looks today, the connectors were actually plugged into the side of the board, much like the home computer PCI connected components.

Some enthusiasts have gotten away from the earlier original ecms, and have supplanted them with the 1227746 ecm used on the 1988-92 TBI equipped V8's.  This requires mating in the later ecm connectors to the original harness.

ECM Service Numbers

1982-1984 5.0 and 5.7L Cross Fire Injection Vacuum Diagrams (NOTE: The Camaro's used a single inlet air cleaner).

1982-1983 Camaro 5.0L Cross Fire Injection ecm diagram

1984 Corvette 5.7L Cross Fire Injection ecm diagram. 1982 similar.

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