Steve Baur
Former Editor, Modified Mustangs & Fords
October 13, 2010

"If your car made more power, you would lean out," notes Turnpaugh. "You were literally just following an exact amount of preprogrammed fuel. With the wide-band meter that the EZ-EFI uses, you can adjust your air/fuel ratio targets, idle speeds, and acceleration pump fuel tables with the handheld.Also, it is self-tuning. You can change cubic inches, the camshaft, or the heads and just drive on. It will relearn the perfect tune on its own." The EZ-EFI will also adapt to changing fuel octane, but it isn't designed for use with ethanol or methanol fuels.

FAST has run the EZ-EFI on modular engines as well, using its XIM standalone ignition controller to run the coil packs-they've even had it running the new 5.0L Coyote engine. The XIM gives the EZ-EFI the correct tach signal it wants, while reading the stock encoder wheel on the motor.

If there is a drawback to the EZ-EFI system, it's that it isn't recommended for use with power adders. The included MAP sensor is only a 1-bar sensor and can't read the higher pressure, and while that is easy enough to change out for a 2- or 3-bar sensor, the second part of the equation resides in the computer's firmware, which doesn't support that range.

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"The engine can go into boost in many different ways depending on whether it's turbocharged or supercharged," say Turnpaugh. "Boost can be almost immediate on a Roots supercharger, and the system would have absolutely no time to tune before it would go lean. So it was decided it wasn't safe to try to do a self-tuning system for that application."

The EZ-EFI also doesn't control ignition timing, so you couldn't pull timing out when the motor came up on boost either. Nitrous oxide is a different story.

"The reason we [don't advise it] with nitrous oxide is because this system is always in closed loop. If you go to wide-open throttle, it tunes to your WOT air/fuel ratio target that you have set. If you spray nitrous, it doesn't know this, and it will try to keep the air/fuel ratio at the target you have selected for normally aspirated. This is normally too lean for nitrous; it would lean the mixture out to an undesirable point. There are guys running nitrous with it, but they're setting their WOT air/fuel ratio to what they want when the nitrous is on," says Turnpaugh. This will obviously work for the track, and conceivably you could change the tune before you drive home-so it's possible, just not recommended.

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Beyond the EZ-EFI, there is the XFI system. This step is usually chosen if the user wants to have complete control over his tuning, or he wants timing control. Also, it offers the user the safe ability to run power adders. The other situation that would require the XFI upgrade would be if the motor offers too little engine vacuum at idle. FAST has only see one situation like this so far, but when you get down to 9 inches or less, you really need to hand-tune the idle area, and possibly even run in Alpha N mode instead of Speed Density.

To see exactly how the EZ-EFI system works with the multi-port retrofit kit, we summoned up our Street Smart Windsor Mustang project, as it offers a non-stock application that utilizes the factory computer system. The '89 GT in question put down a respectable 300 rwhp and 360 lb-ft of torque when we baselined the car on the TunersInc Dynojet dynamometer. From there, we moved SSW over to the Hurricane Performance shop, where Jason Combs handled the EZ-EFI installation while we took the snaps.

We've used both of these shops on numerous occasions in the past, and they always deliver top quality work in addition to going the distance to satisfy our ridiculous magazine requests. Combs knocked out the install with ease-the most difficult modification was locating the right wire to trigger the fuel pump.

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