Dale Amy
February 1, 2004

Horse Sense:
Tuners having fits getting '02-and-newer Mustangs to run well after modification should take a close look at PCM Editor. This software program provides access to new factory programming schemes-such as torque and exhaust modeling-that usually defeat traditional methods of electronic tuning.

Tuners, listen up. How'd you like to tune more efficiently and thoroughly? From what we've recently seen and experienced, Pro-M Racing just may be able to help you out with some powerful new software. But let's bring the rest of the readership on board first.

Ask any tuner what tops his wish list to help in the task of tuning for major Mustang modifications, and a likely answer would be "more precise control." The more precise control a knowledgeable tuner can exercise over the computer processor that so rigidly dictates a modern engine's operating characteristics, the better he can make that engine perform. This is true not only from a pure power perspective, but also from the equally important aspect of driveability, and even emissions cleanliness. When it comes to tuning, a scalpel is a better approach than a broad sword.

By now, you probably realize that fuel-injected Mustang engines do only what their EEC IV or V processors tell them to. Without this computer-and specifically, the calibration programming found in its Read-Only Memory-the engine simply wouldn't run. The ROM (or, more correctly, the Electrically Erasable Programmable Read-Only Memory) is chock-full of programming code, including the critically important air/fuel mixture and spark-timing strategies, designed to deal with the wide variety of conditions an engine encounters. The tuner's unenviable job is to reprogram this EEPROM (by way of a chip attached to the EEC's J3 port, or edge connector) to take advantage of, or compensate for, the engine modifications we love to spend our paychecks on-especially the ones that really throw factory calibrations out of whack, such as power adders, big cams, or higher-flowing injectors.

The basic problem for Mustang tuners is that all you get when you try to read the factory EEPROM programming is a bunch of hexadecimal gibberish. Like an encrypted message, all the calibration information is there-all the switches, functions, scalars, and tables that the factory programming utilizes-but in indecipherable form. For instance, the tuner may know that he wants to richen air/fuel ratios by a certain amount at full throttle, but how does he know where to go in the program to do it? Traditionally, tuners have relied on aftermarket performance chip manufacturers, who have deciphered key portions of this factory programming code-so that they know, for instance, where to find and alter some of the air/fuel or ignition timing lookup tables. But most of these manufacturers have kept that knowledge in-house and out of the hands of the actual tuners themselves.

In this scenario, a tuner working on a car must communicate by phone to the chip manufacturer what he'd like to see in terms of-say-timing or air/fuel ratios under given conditions, but the actual programming changes are done by the manufacturer's staff. The new program is then transmitted by modem back to the tuner to be burned onto a chip. This process is repeated as necessary until a satisfactory tune is arrived at, eating up valuable time-and time is money.