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Fox Body Computer Chips - Facts & Fundamentals

Written By: Connor MC

Shop Fox Body Chips & Tuning

The overall performance of your Mustang depends on a quality tune, whether you are building a track monster or restoring a stock Fox back to its original glory. Ensure your car is running at peak performance with a custom chip and Bama tune.

Shop ECU Chips

A Fox Body's computer restricts the amount of power your engine can push. An aftermarket chip and tune will go a long way lifting the stock computer's limitations.

American Muscle

Facts About Fox Body Computer Chips 

  • The Engine Control Unit is designed and programmed to run the car under all conditions
  • Aftermarket chips and tunes are keys to achieving maximum performance from your Mustang
  • Chips and tunes are specifically designed for your engine combination
  • Chips and tunes become necessary when you modify your Mustang’s engine through heads, intake, and cam swap

What is a Mustang's ECU, and What Does it do?

Quick and dirty, ECU is short for ‘engine control unit’ (also called ECM, and PCM – short for engine control module and powertrain control module). Essentially, it is a computer module designed and programmed to run the car under all conditions, at maximum efficiency. Some tasks of the computer are, among many others:

1. control fuel delivery (right amount at right time)
2. control spark timing
3. exhaust gas circulation and oxygen content

All of these parameters are monitored by 22 different sensors placed throughout the engine. Disregarding all of this technical jargon, a car’s computer is really like a central brain. It will control how the car operates at idle, under load, and at wide open throttle. The reason cars are so reliable under all conditions nowadays is because of the use of these engine control units.

Your Fox Body Mustang's Computer

The specific unit Ford developed and used in their Fox Body Mustang was the EEC-IV computer. Composed of a 16-bit microprocessor running at 15 mHz and 16 kilobytes of read-only memory (ROM), the EEC-IV was still capable of processing over 1 million calculations per second!

The EEC-IV computer debuted in the Ford Mustang in 1983. Running all the way until 1993, the stock EEC-IV ECU is actually a very versatile and competent system. The stocker actually does a very good job at adjusting for many different modifications. However, the stock EEC-IV does leave a little power on the table – it is, after all a factory piece and therefore optimized for greater efficiency, reliability and emissions control (basically it is conservative).

Tuning Your Mustang for Maximum Performance

The fix for this is to go with an aftermarket chip and tune. The benefit of running an aftermarket chip and tune is that they are designed specifically for your engine combination, optimizing all the parameters necessary to run the engine at its best for its intended use (be it strictly street, track or a combination of both – small changes here and there can produce an entirely different monster). Before dwelling deeper, let us first examine the stock computer. As stated, it is a pretty stout system and changes are unnecessary until a certain point.

Mustang Speed Density Systems vs. Mass Air Systems

Fox Body Mass Air Flow Meter By BBK
Mass Air Meter

The EEC-IV computer works in conjunction with another type of engine control system, depending on the year of the car. 1987-1988 Mustang (excluding 1988 Mustangs sold in California) came equipped with a speed density system. Mustangs 1989 and on came installed with a mass air system (still used today). The difference between these systems is simply the way they measure incoming air. The speed density system is actually a ‘dumb’ system – it does not actually measure the air. Rather, it uses a formula and a premade lookup table of values. A mass air system does measure the incoming airflow, and the EEC-IV makes the corresponding adjustments based on the live measurements. In terms of performance, a speed density car is said to be quicker when both are stock. However, speed density systems are not as modification friendly (particularly with camshaft changes!). For this reason, it is highly recommended you convert to a mass air system when you begin modifications.

When to Consider Getting a Chip and Tune

As already said many times, the stock ECU is quite good at adapting to basic mods. However, from the factory Ford intended their vehicles for the emissions conscious states and individuals. Installing a chip and custom tune will show horsepower and torque gains on even a stock Fox Body. Basic changes like exhaust, throttle body, or addition of a cold air intake, for example, will be better accounted for by the computer and work more efficiently together as a system. A chip really becomes useful when the engine is revamped via heads, intake and cam swap. That is where you will notice the greatest power, efficiency and overall driveability gains. Some of these engine mods cannot successfully be completed without a chip and tune!

What Performance Mustang Chip Will Get the Job Done?

Fox Body Computer Tuning Chip
SCT 4-Bank Eliminator Chip

Now, a very popular (and actually economical) chip to tie your top-end mods together is the SCT 4-bank Eliminator chip. This chip plugs right into the J3 port of the stock EEC-IV ECU (located underneath the passenger side kick panel) and comes with free tunes for life from Bama Performance. Perhaps the best feature about a chip setup like this is you can switch tunes instantly, simply using a switch. The chip will store several tunes and any can be accessed and run instantly via flipping a switch rather than having to connect a laptop computer each time and transfer over a different tune.

How Do I Get My Tunes?

Bama Mustang Performance Free Tunes For Life

You simply send in exactly what parts and specifications are used in your car. Bama has dialed in nearly every combination of mods and will create three custom tunes specifically for your car. A service just as good as strapping the car to a dyno and at a fraction of the cost over the life of the vehicle makes Bama the top tuning service for Mustangs worldwide.

No doubt about it, if you are seeking to really tie your engine combination together, perfect power and torque, better efficiency and ultimate driveability, consider using a 4-bank SCT Eliminator chip. Install is fast and painless (plugs right in to the stock EEC-IV J3 port). With the accompanying Bama Performance tunes, at the flip of a switch you can have a tame street driver or an all out performance machine. For many, a chip and tune is the best bang-for-your-buck purchase you can make.