Considering that the GT500 will be getting an engine very similar to the GT, I would like to discuss the differences between the two engines and how those differences will affect the horsepower of the production GT500.

The GT is rated at 550hp, but articles such as this one, Enzo v. GT v. Porsche , suggest that the engine is making closer to 650hp, which is also confirmed by doing the math.
3458 lbs + driver ran 11.2 @ 131 = 650 hp.

So, what horsepower will the production GT500 actually have? Let's consider the following:

What is the same?

1) Displacement (330 c.i.d)
2) Compression Ratio
3) Heads and possibly cams
4) Forged rotating assembly
5) Intake?
6) Intercooler?

What are the differences between the GT engine and the GT500?

1) Supercharger: the production GT500 will possibly have an eaton at 8 psi v. 12 psi twin screw.
2) Block: GT500 will have a wet sump iron block v. dry sump aluminum block on the GT.
3) Injectors: GT500 will have one injector per cylinder vs. the two injectors per cylinder on the GT
4) Exhaust: The GT500 will be different, at least by geometry.

I’m sure there are some other minor differences.

Assuming approximately (23.5 hp per psi of boost) we loose 94 hp from the GT engine just from lowering the boost.

Wet sump vs. dry sump, I'm guessing we loose another 30 hp.

Total HP loss = 124 HP

This would indicate the GT500 engine could produce 526 hp.

Am I missing anything? Please feel free to criticize my guesstimates, and I will adjust the numbers based on the most logical approach to the problem.

I believe that the GT has a higher redline (6500 vs 6000).

So if torque is perfectly flat at 475 ft-lbs:
hp = tq * rpm / 5252

hp@6500 = 587
hp@6000 = 542 (-45)

This is a very poor estimate since I have no clue what the torque curve looks like for the 5.4L but it gives us an idea of the losses.

Come on now, someone has had to dyno the car by now. I don't know how much faith I take in a Motor Trend article.

svtperformance.com has a thread where a couple of GTs have dyno'd 530-560 rwhp.

This looks like a good breakdown, but Car and Driver said the blower would have a peak of 10 psi. With a Roots type blower, I'm guessing 10 psi at 4000 rpm and 8 or so around 6000 rpm. Considering peak torque will come in around 4000 rpm, I'm guessing 550-575 lbs of torque at the crank. Peak horsepower around 5500 rpm with 530 HP at the crank. The twin injectors won't add power, only limit it. I'm curious why they lowered the rpm limit on the GT500. The guts are the same and the iron block should be stronger than the GT40.

I realize these are rough estimates, but don't forget that a twin screw will typically make more hp with the same psi relative to a rootes, so any correction needs to be slightly biased to take this into account. I will be surprised if the GT500 isn;t at least knocking on 500hp's door.

Here's how I want the math to work out...

My '03 made 415 rwhp with a K&N and cat-back. The 5.4L is about 17% bigger, so all else being equal I'd like 17% more power -- 487 rwhp. Plus the extra 2 psi of boost, figure another 20 horsepower or so. Say ~500 rwhp with just the filter & a cat-back, I could be very happy... that's getting near the 600 bhp mark.

And then the pulley gets swapped... :) :) :)

Dave

SVT learned their lesson a few years ago when they overstated hp once.Everybody howled ,so they might understate things a bit.Also if you come out and say over 500hp the insurance co.s start to bust our chops(they will anyway). The dyno stories will be great.

05 Mustangs and Super Fords just mailed the August 05 edition magazine, and in it they tested an 05 Mustang GT with a Kenne Bell with different boost levels. At 9 psi the Mustang made 478hp at the rear wheels. The author made the comparison to what a 5.4L engine would make at the rear wheels given the same boost level and engine efficiency. He concluded that the "lightly stressed" 5.4L would make 561 RWHP! (assuming the same 103 HP per liter) I have a feeling we will be see some big numbers from the Shelby in 2006.

Too bad its coming from the factory with a roots. =/