Project MILF 2006 Ford Mustang GT Gear Install - Fueling Around - Tech

A wise man once said that when you reflect on your marriage and remember happy times, it's how you handle the rough patches that allows your marriage to stand the test of time. The same can be said for a family project car. Being able to deal with the ups and downs of adding parts on your car for the sake of increased performance is crucial to keeping your sanity.

Case in point is this month's installment featuring our '06 Legend Lime Mustang GT, Project MILF. Let's recharge the batteries for a moment and bring you up speed as to where our beloved Mustang lies. What started out as a bone-stock, automatic transmission-equipped S197 GT has been transformed in a series of stages. We began with the installation of the Ford Racing Performance Parts Handling Pack before lowering a Whipple supercharger and accom-panying FRPP Super Pack parts on top of the Three-Valve mod motor. We then ditched the factory exhaust for a set of Stainless Works long-tube headers and a full-on exhaust system.

This month, we decided to go down what we thought was the easy route and ditch the stock 3.31 gears in the Stang's 8.8-inch rear, replacing them with a more aggressive 4.10 gearset. With a best elapsed time of 12.47 seconds with the highway-friendly 3.31s, we figured by putting in the 4.10s, the car would get out of the hole quicker at the track and we'd drop e.t. in the process. The numerically higher gears allow the car to 60-foot better, as well as climb through the rpm range quicker due to their offering a greater mechanical advantage. Also, the 4.10 gears would let the engine achieve a higher speed going through the traps, thus keeping the motor in the sweet spot of maximum horsepower production.

We once again piloted the retro-Stang to Crazy Horse Racing, where mechanic Glen Knell handled the chore of swapping out the gearset. Before we set upon swapping gears, though, we realized that once the 4.10s replaced the 3.31s, the computer would need to be recalibrated to accommodate the lower gear ratio. If you don't recalibrate the computer for the new gears, you can actually cook the clutches in the transmission. The vehicle speed sensor will operate with the mindset that the car still has 3.31 gears in the rear instead of the 4.10s. The engine may also rev so much more quickly that it will hit the rev limiter before the computer commands it to upshift. With the vehicle speed sensor being off when compared to the actual vehicle speed, upshifts and downshifts of the transmission will also be erratic, and hard driving or extended periods of cruising will cause the clutches in the trans to overheat and eventually fail. With that in mind, we picked up the telephone and had tuning guru Job Spetter Jr. of Turbo People meet us at Crazy Horse to help us with the tuning aspect of the car.

While the actual gear swap itself was fairly straightforward, we ran into a bit of difficulty tuning the car. According to Jesse Kershaw at FRPP, there is a recalibrating service offered where you can easily recalibrate the computer when you swap in the gears. "You fax us information with your new gear ratio and we overnight you a new calibrator," he says. "Once you load the tune in, you mail back the old tuner."

The recalibration service is $75. Added into the cost is the $250 core charge that, once the original tuner is returned to FRPP, is credited to your charge card. The problem is the tuning service isn't available for those who put the FRPP Super Pack on an automatic car like Project MILF. With FRPP not having a way for us to recalibrate Project MILF's computer for the gears (at this time), we were forced to have Spetter create a custom tune for the car.

At first, Spetter tried to load the new tune on top of the FRPP-supplied supercharger tune. When he cranked the key, however, the engine did not fire. The FRPP-supplied tune is a locked program, meaning that for us to load a new one into the car, we had to remove the FRPP tune and return the program to stock. Once we figured that out, we thought that things would work like butter. Think again. After Spetter replaced the FRPP blower tune with the stock tune, he used an SCT XCalibrator2 to remove said stock tune and replace it with a conservative baseline one. The car started, and after we took it around the block easily, making sure there were no unwanted noises coming from the rear end housing, we strapped Project MILF to the dyno. We not only had to recalibrate the computer for the gears, but basically had to start from scratch and create a custom tune to wring the maximum amount of ponies out of the 4.6L engine.

Spetter started with a conservative fuel and timing curves but realized halfway through the first dyno pull that the car was extremely lean, and he pulled the plug. He was looking for the air/fuel ratio to be in the high-11 to low-12 range. "I adjusted the air/fuel ratio by playing with the fuel trims as they are related to the MAF signal," he says. "With the MAF being repositioned and the blower obviously pushing in more air than before, the MAF signal and the fuel were way off. To correct this, I adjusted the fuel trims to try and match them up to the MAF signal."

Therein lay our problem. On the second dyno run, Spetter watched as the air/fuel ratio went to the moon quicker than Apollo 11. Even though Project MILF made 319 rwhp, the car was dangerously lean at high rpm. Equipped with the stock GT pump and the 32-pound injectors supplied with the blower kit, the engine simply wasn't getting enough fuel, nor could he command it to do so. "At 4,900 rpm, the fuel pump was maxed out at 100 percent," Spetter says. "At 5,500, the fuel injectors were at a 100-percent duty cycle. By that time, the fuel system was pumping as much fuel into the engine as it could. The problem is, the engine needed more fuel at higher engine speed than the fuel system could provide." The result was the engine starving for fuel from 5,500 to 6,500 rpm. Spetter kept the engine from hurting itself because he still had a sizeable amount of timing out of the engine.

"The injectors are fine to 500 hp, but the pump is the weak link," Kershaw explains. With the ambient air temperature on this day being 90 degrees Fahrenheit, the engine itself equipped with a non-intercooled supercharger, and the car being dangerously lean at high rpm, it didn't make sense to take Project MILF down the Old Bridge Township Raceway Park quarter-mile, as we would have caused some serious engine damage to a car with a little over 2,300 miles on the odometer.

With a dire need to get the car running so the kids could eat, Jim D'Amore of JDM Engineering took on the task of seeing what we could do to try and rectify the problem. Our original thought, while confusing to us, was that the car needed either an upgraded fuel pump like the one found in the GT500, or a set of Ford GT injectors. In the end, neither a part nor a piece was needed. D'Amore strapped Project MILF to the dyno, uploaded a tune that had as much fuel as possible going into the engine, and cranked up the Three-Valve. Through the scan tool he was using, he noticed during startup that the charging system for the car was pumping out only 12 volts. After running through a few diagnostic checks, it was determined that the alternator was not working. With the alternator not putting out the usual 14 volts, the fuel system-especially the fuel pump-was seeing only the 12 volts produced by the battery. "The alternator wasn't operating at full capacity," D'Amore explains, "so the car is obviously going to run lean. With the system down on voltage, the signals will be weak to the computer, as well as the injectors."

The voltage got below 11.99 volts at one point, causing the battery light to come on. "The ideal setting, since the alternator is computer controlled, is that at 0 degrees ambient air temperature, the charging system will see 14.6 volts," D'Amore says. "At 90 degrees, you will get 14.1 volts, and at 170 degrees, 13.3. With the bad alternator, the car was seeing 12.8 volts at an idle."

We swapped out the bad alternator, and things got better as quickly as a Top Fuel car making it down the 1,320. With the charging system finally registering 14 volts, D'Amore played with the tune, eventually getting the car to rip off 385 rwhp and 368 rwtq. "I still have the tune a bit soft," he says. "I went with a conservative timing curve. If I had a full day with the car, I could get the power closer to 400 rwhp just by getting the timing perfected." If D'Amore is correct, Project MILF should be able to sneak into the 11-second zone with the revised tune. Not bad for a daily-driven grocery-getter.

Even so, with the tune itself, the car picked up 50 rwhp and 60 lb-ft of torque. To say that's a lot would be an understatement. The result at the track was noticeable. After spinning hard on our first few rips with the stock wheels and tires, we borrowed a set of Mickey Thompson 275/40/17 drag radials, which were mounted on a pair of 17x9 Cobra rims. Once we bolted on the drag radials, Project MILF roared to a 12.200 e.t. with a trap speed a tick under 115 mph. Our 60-foot time dropped to a 1.746, which is awesome considering the car weighs 3,650 pounds without a fat-cat MM&FF editor behind the wheel. As a matter of interest, cruising rpm was raised only 500. Before the gear change, the tach registered 1,750 rpm at 60 mph. With the 4.10s, the tach needle moved up to 2,250.

While Project MILF may have had us in the doghouse for a few days, not only did we get out of it, but we decided to stop at a jewelry store along the way and pick up a make-up present in the form on an intercooler. That should bring a smile from the wife for sure.

Still Counting Dollars
We're keeping tabs on how much money we put into Project MILF. After all, we can't blow our whole paycheck on car parts. Keep in mind that this tally includes prices for parts only. The original cost of the car and labor rates are not included as there are variables to both figures.

On the Clock
After our last foray to Old Bridge Township Raceway Park in Englishtown, New Jersey, we were able to discern how much the headers and exhaust were worth on Project MILF. For this installment, it's hard to discern how much the gears alone were worth due to the fact that we could not just recalibrate the computer for the gears with the FRPP-supplied tune. We had to create a custom tune for the car, obviously taking into account the new gears. In the end, though, it was worth it as Project MILF screamed to a new best. In the following chart, the first number is the difference from the previous modification, while the second number is the difference from the baseline. Can you say 11s?