Volume IX, Issue 11, Page 66


Racing With The Black Box

You can check out Part 1 of this series here.

Peel open the hood of any new built-by-Detroit car, take one look at the labyrinth of wires, sensors and foreign objects, and for most racers, it's time to beat a path back to a simple double pumper. Unfortunately, that could prove to be a big blunder. Buried beneath all of the electronic chaos are engine combinations that beg to be flogged on the drag strip.

That's the story behind the fuel injected LT1 Firebirds which have tearing up Stock Eliminator. So what's their secret? That's easy. It's all inside the "black boxes" built by ACCEL, FAST and most recently, the folks from MSD. Since the 1993 model year, factory engine management computers or "ECUs" no longer incorporate removable "chips" or proms. Because of EPA mandates, the latest Detroit ECUs incorporate "flash proms" which cannot be reprogrammed, or at least, reprogrammed easily (Detroit is bound not to reveal computer hierarchy or electronic addresses). This is no problem for the racing aftermarket. Since these cars are "off road" applications, they simply replaced the factory ECUs with their own spark/fuel management systems.

The 1994 model year saw General Motors switch from a relatively simple batch fire fuel injection process to sequential fuel delivery. Under the batch fire method, fuel is injected into the engine through eight injectors simultaneously (two times per crank revolution). The more exotic sequential system injects fuel into each cylinder based upon the position of the crankshaft. Sequential fuel injection is obviously superior, but most of the inherent advantages occur during warm up as well as part throttle operation, and have little to do with maximum horsepower. In a drag race application, the engine operates primarily at wide open throttle. Because of this, most of the ECUs used in Stock Eliminator are designed to operate under the simpler batch fire process. Overall driveability and part-throttle response is still excellent, and can easily be adjusted to suit the needs of both the combination and the driver. That's not to say, however that a sharp racer couldn't exploit the advantages of sequential injection. There may be engine acceleration issues that only a sequential system can address.

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