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.
To keep the ring gear from...
To keep the ring gear from trying to exit the back end of the housing, we installed Ford Racing Performance Parts' new rearend girdle (PN M-4033-62). The good-looking girdle has two adjustment bolts that keep pressure on the main caps, thus keeping the ring gear in the proper position. Thanks to the decreased distance between the Panhard bar and the rear cover in the S197 cars as compared to that of the SN-95 cars, FRPP had to develop a rearend girdle that was thinner than previous models. While this part was designed to fit the S197 cars, it will fit all year 8.8-inch housings.
With Project MILF rolling...
With Project MILF rolling off the assembly line with a set of 3.31 gears, we knew that switching to a set of 4.10s would greatly improve application of the now-supercharged Three-Valve's power. The gearset we got from FRPP came with an install kit that included all seals and shims needed to set the backlash at the correct amount.
Glen Knell at Crazy Horse...
Glen Knell at Crazy Horse Racing performed the gear swap. After getting the car up on the lift and removing the rear wheels, Knell disconnected the sway bar and moved it out of the way as it would greatly impede his ability to remove the ring-gear assembly. He also loosened and moved the Panhard bar.
Knell removed the bottom four...
Knell removed the bottom four bolts on the stock rear cover and drained the rear fluid. Once the housing was emptied of gear lube, he took out the remaining bolts and removed the cover.
With the ring gear and differential...
With the ring gear and differential now exposed, the next item on the to-do list was to remove the C-clips and center pin from the differential. Knell took out the C-clips with a magnet.
Knell removed the brake calipers...
Knell removed the brake calipers and rotors. He then pulled the axles out of the differential.
At the front of the rearend...
At the front of the rearend housing, Knell removed the driveshaft from the yoke bolted to the pinion. He then took off the yoke from the front of the pinion gear so he could remove the gear later.
With everything undone, it...
With everything undone, it was time to take out the ring gear and differential. The two came out as an assembly, requiring a few tugs.
Once the ring-gear/diff assembly...
Once the ring-gear/diff assembly was out of the housing, Knell separated the 3.31s' ring gear from the stock differential. Since Project MILF is daily-driven with only 2,300 miles on it, we left the differential alone.
Knell took the 4.10s out of...
Knell took the 4.10s out of the box and ran them through the parts washer to get off any impurities and left-over Styrofoam packing. Once the ring gear was cleaned and dried, he mated it to the differential.