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.

In other cases where programming software has been provided to tuners, that software has, according to Pro-M, apparently not always decoded enough of the switch, scalar, and lookup-table locations of the factory calibrations, especially on newer cars. This can create a situation where a tuner may think he has successfully modified wide-open A/F ratio tables, only to find those changes are being overridden by some undiscovered switch or function buried deep in the OEM calibration code.This incomplete descrambling of the EEPROM code-translating into a lack of complete control-has frustrated some tuners to the point where they take the rather drastic step of tossing out the EEC processor altogether and substituting a more easily tuned, aftermarket, stand-alone EFI system for their heavily modified subjects.

To us, this seems like throwing out the baby with the bathwater, since the factory focuses a whole lot of engineering expertise on developing each engine's particular calibration strategies for maximum all-around efficiency. Instead, if a tuner can retain those basic, well-researched strategies and algorithms, and simply tweak them as necessary to compensate for a particular car's modifications, he should theo-retically be able to tune for both ultimate performance and impeccable driveability.

Which brings us to our point. The folks at Pro-M Racing figured that what tuners really want and need is user-friendly software that translates just about all the EEC's hexadecimal ROM gobbledygook into plain language. It is presented in a form that is easily understood and edited using a simple Microsoft Windows interface that permits the tuner quick-and surgically precise-manipulation of engine operation from cold-start right through to full-throttle, even on the devilishly tough '02-and-newer cars. They call this powerful tuning tool the Pro-M PCM Editor [Finally, an editor with some power.-Ed], and what follows is merely a surface-scratching look at what it can do. Interested tuners should contact Pro-M Racing for a more detailed and intelligent discussion of its capabilities. As we understand it, when teamed with Pro-M's accompanying hardware that allows reading EEC EEPROM and burning chips, it seems a tuner can have a near-factory level of tuning control right in his laptop. This is good news for both tuners and tunees. Read the captions to find out what this stuff can do for your Mustang.

Putting It To The Test
To get a feel for what the PCM Editor software is capable of, we rolled our Paxton-blown '95 GT into the Pro-M Racing shop, not because we were dissatisfied with the way it was running, but because Pro-M's tune-meister Scott Beer said he could make it run even better.

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The previous strategy to tune the car had been as follows.

• SPOUT connector removed and timing locked at 29 degrees (base and total)
• Idle set somewhere around 900 rpm (to eliminate a previous hot-idle stalling problem and smooth out the idle-enrichening effects of our 40-lb/hr injectors)
• An MSD 6-BTM box for boost retard

Frankly, the car ran fine with this tune, but we were a little troubled about the fixed timing, knowing that the factory programming radically alters timing advance based on load and a myriad of other operating con-ditions. It does this for good reasons, such as power, economy, and driveability.

Even the demise of our 6-BTM box a couple days previously didn't discourage Scott, who said he could retard timing through one of the various EEC timing tables. So we replaced the dead ignition with a simple 6-AL box and forged ahead.

After pulling the previous chip, Scott's first step was to reinstall the SPOUT connector (so that the EEC once more had control of spark advance) and set base timing back to a factory 10 degrees. Using the PCM Editor software with the definition file for our particular T4M0 calibration code, he then adjusted the various factory timing tables so as to be conservative under our Novi's 10 psi of boost, but otherwise aggressive for crisp response.

Scott then entered the specific flow data from our existing Pro-M 80mm meter (calibrated for our 40-lb/hr injectors) into the MAF transfer function data screen. With an NGS scan-tool connected, he also monitored the short- and long-term fuel trim read-out, and then made the appropriate corrections on yet another PCM Editor screen, leaving idle rpm at factory normal. Wide-open-throttle air/fuel mixtures under boost were set and verified at 11.8:1. All this took little time, compared to more traditional methods.

Unfortunately, we couldn't dyno test the GT in "before" condition because of the lack of boost retard with the new 6-AL ignition, so our pre- and post-operative comments have to be subjective, without objective backup. That said, the car now feels decidedly crisper under part throttle, and its cold- and hot-start manners are, if anything, better than stock. Perhaps the best way to describe its flawless overall driveability is to say that, other than the giveaway whine, there's no way to tell there's a supercharger on the car until your eyeballs start to flatten under boost. And that's a high compliment.

Seat-of-the-pants feel under full boost is currently tempered by the fact that our (stock, original) clutch is now slipping. But we can confirm that the GT now gets at least 2 mpg better on the highway than it did before-no doubt a benefit of reverting to the factory timing strategies under cruise conditions.

Scott is no doubt an excellent tuner, but the PCM Editor software has provided him the tools to tune better than ever. And it can do the same for other tuners out there.