Today Jerry and myself got the opportunity to work on a gentleman's brand new GT500. With just over 1000 miles on the odometer the car still smelled like new.
All runs were done on an industry standard Dynojet 224x, you can't fudge these #s like other dynos. 93 octane pump fuel was in the tank.
We ran the car 3 times stock to get the drivetrain up to temp and get a good average HP #. The car made 421/438, then 424/427, and 419/22. I would say the blower and engine are very sensitive to heat soak.
On every run we monitored air/fuel with two widebands, boost after the blower/intercooler, and restriction before the throttle body. We also datalogged a myriad of parameters with the SCT X-Cal2 and Live Link datalogging software.
The stock tune has no timing in it at all, it's really quite disgusting. With the stock tune the air/fuel came in a little lean below 2000rpms, ran 11.5 through the mid range, and hit high 10s past 5000rpm. The car makes about 9psi of boost in stock form, just like the guage on the dash says. With the stock airbox the MAF is almost pegged, reading 4.95v.
Now that we had some good data on a stock car we started playing with the tune. When it was all said and done we arrived at
482RWHP and 477RWTQ, no you're not reading that wrong, that is approximately a 60RWHP gain. This was not a money shot either, the car was ran 11 minutes before and made 481RWHP/476RWTQ on the previous run. This was no ragged edge tune either, the Air/Fuel was 11.5:1. I was not about to blow up a brand new and very expensive car just to be an internet hero. We did not have time to let the car cool for a money shot. I was so excited that I started on the intake install right away.
I whipped up a prototype intake the night before with parts I had laying around. I took a piece of 4.5" aluminum tubing, a 4.5" cone filter, and a little CNCed aluminum flange that I had made a while back. The flange allows you to mount a slot style mass air sensor into a tube. It wasn't much, but it would give us something to play with. We had to retain the stock tube that passes between the Strut Tower Brace and valve cover. The tube is rubber with a plastic insert to keep it from collapsing, I'm sure it's restrictive, just like the stock airbox and panel filter. An aftermarket tube with thinner walls would flow a lot more air and still fit between the valve cover and STB.
The air intake required some tuning because the mass air sensor was installed in a new tube. This totally throws off the air/fuel and requires that the maf transfer function be redone, however an experienced tuner can do this in a few pulls. With the prototype intake the car made
505 RWHP/487RWTQ. Simply amazing, with the new intake the car picked up a slight amount of boost past 3500rpm, about 1psi peak at 6000rpm. The sensors were still measuring a little bit of intake restriction though, so the rubber tube between the maf housing and throttle body definitely has to go. I ordered a piece of 4.75" silicone hose, but it did not arrive until after the dyno testing was done today.
Tune with stock airbox vs tune with air intake, shown with boost.
Stock vs tuned vs tune+intake shown with air/fuel.
This car has a supercharger inlet pressure sensor between the blower inlet and throttle body, this will be handy for measuring various inlet restrictions. In the next few weeks I should have a throttle body to test.
The best part is the car feels just like stock until you romp on it. A quick 1-2 shift can now get you in trouble, even with TCS on.
We disconnected the exhaust after the X pipe, it was only worth a few HP.
I've debated whether or not to post this pic of the intake I made. Namely because its very simple and easy to duplicate. However, since I'm mainly in the tuning business I've decided it does not really matter.
A word of warning to all Shelby GT 500 owners out there. This car has a totally unique electronic control system, not seen on any other Ford (not even the Ford GT). The drive by wire system will take power away if you pulley the car, and then add it back in slowly. The car could be given what is thought to be a *safe* tune on the dyno, but then blow up a few days later.
I am still looking for several more of these cars to work on. If you are in the Central Florida area contact me.
