E-Prom Hot; How to get yourself in the chips

Simple installation-easier than changing a spark plug-produces dramatic results immediately. Tests for this article, performed with a 1991 305cid Camaro, showed quarter-mile e.t.s drop by as much as 0.6 second- with nothing more than the chip swap

On the surface the plastic computer chip seems no more complex than poker chips you might pick up in Las Vegas. Looks are deceiving, though.

Encoded into silicon circuits inside the unit, the chip carries instructions-drag strip DNA, if you will-that govern fuel delivery, spark parameters, and a host of other engine functions.

The chip is made in layers. Lasers and micro-machining operations create the circuits and install minute transistors. Next, the chips are programmed with units of information, each unit called a “byte.”

Chips for the Buick Grand National and ’85 Corvette contain some 32,000 bytes, while ’86-and-later GM TPI engines use chips programmed with 156,000 bytes of data.

The programming allows the chip to serve as a reference point for the car’s computer, juggling the variables of throttle position, manifold pressure, engine rpm, coolant temperature, and more. The chip tells the computer how much juice the fuel injectors should deliver, where ignition timing should be, whether to turn off the EGR, and even more specific combinations of variables.

BURNERS

To program a chip, technicians use a device called an E-Prom burner. Using a pair of contacts, the burner zaps a tiny amount of voltage to a specific area of the chip, called an address, to create one byte in the chip’s memory. The burner also reads and prints out information on a chip that has been programmed previously. The burner also will copy information from a programmed chip onto a blank chip, much like dubbing an audio cassette.

Obviously, how well a chip performs depends on how well it has been programmed. Programming is what separates the hot from the not-so-hot. E-Prom programming is an art, a science, and a bit of black magic. The fine line is to program for aggressive performance without compromising other factors.

While the E-Prom burner can show you how a chip has been programmed (although you’ll need factory calibration tables to make any sense out of the printout), it also exposes one of the scams in the chip business, the practice of selling blank chips.

Installing a chip that contains no programming causes the computer to go into the “limp-home” mode, which allows the car to run in the event of chip failure.

Limp-home relies on engine parameters that are hard-wired into the computer’s circuitry. This mode puts the engine into full rich, full advance. Certainly the engine will run stronger in limp home mode, but it becomes subject to potentially damaging spark knock and other problems. A few get-rich-quick companies also offer chips as part of various performance packages that require fuel and intake modifications, possibly a cam swap and a less restrictive exhaust system. In most cases, the greater the scope of modification, the higher the performance. However, the gains come with a price tag. It’s difficult to determine just how much performance gain can be attributed to the chip itself.

To determine what kind of performance boost results from a basic chip swap, a bone-stock 1991 305cid/automatic-transmission Z28 Camaro and a fistful of E-Prom chips were taken to Old Bridge Raceway Park in Englishtown New Jersey.

Launch technique involved powerbraking the car to just haze the tires to the tree, then nailing it. For consistency, the shifter remained in Drive on every pass. A baseline was established with a consistent string of 15.20s at 92.0 mph. Three runs were made with each chip, and the best number was recorded. The engine was allowed to cool between runs.