This guy apparently has already dynoed his car, both with a baseline then again after changing the mufflers and gears.....

http://www.stangsunleashed.com/forum...opic=2230&st=0

 

wow.... an extra 33.6 rwhp from an axle back...looks like a lot of promise

 

Or a lot of incorrect numbers. How can you gain that much from exhuast swap. We need to see #'s from additional people. And even more important, let's see 1/4 mile #'s.

 

this all doesnt make sense, 412rwhp....no no no...something must be wrong

 

Maybe he is in the exhaust business, and is telling everyone how much of a "gain" you can get from his...

 

its just a Flowmaster axleback, which makes me believe one of the set of runs is way off, that would be roughly 34rwhp gain for swapping out a muffler,

pic: http://www.stangsunleashed.com/forum...e=post&id=2025

I would lean more towards the first set of runs being a bit off, especially since the car only has 250miles on it, the comp isnt even done learning the engine and the revs, fuel/air ratios, ect.

if anything the second set of numbers are promising, even if the axlebacks gained almost 35rwhp, but probably more realistically Ford underrated it a bit and the mufflers gained at best 5hp and the car is actually closer to 520-525 HP at the crank

one person on that thread reported a Ford GT500 tech saying that it is actually closer to this 525HP at the crank, the extreme humidity and the heat could also damage the numbers a bit, but I think that the reason he finally saw the true numbers of this car is because of the 4.10s he put on, pulling that power into a more noticeable lower range of the power band since the darn computers on these cars limit everything as we all know by now, including limiting the revs before reaching peak power. On the Shelbies the rev limiter is suppose to kick in around 6250 RPMs and, as this was all discussed on the original thread already for those that read it, on the first set of runs the peak HP probably wouldve occured between 7000-7500 RPMs. So like the original poster of the thread stated it is very likely that the car comes stock around 525HP at the crank, you just cant see it until you at least reflash the comp and get rid of the limiter or raise it. And if thats the case this is a bad **** car, especially since all you need is a tuner to change the limiter, and since youre doing that you might as well increase the throttle response and lean it out a bit to get even more HP while you are at it. And if it holds true to what the 05-06GTs did with a retune, it could possibly get to 550 at the crank for a $300 tuner, NICE!!!

 

If you read the story...
The guy drove it there, and then baselined...
...then it sat for 2 hours while they installed the gears and mufflers....
Cooling off....

What he shoulda done was drove the car there, waited 2 hours....baselined....
Then put the other parts on....and see the difference.
It would not have been such a huge jump.

Who know how hard he was on the car before getting there.
I know if I had a Shelby brand new, I'd be flogging it a bit ...
Heck...even my 05 GT heats up like a ****

No way he got THAT much horsepower from a set of blowmasters.
Let alone ANY other axle back. It cannot be corked that much.

 

WHERE'S THE TORQUE??? Those numbers seem low for a supercharged 5.4.

 

he posted the torque:

RWHP: 446.5 RWTRQ: 421.9

given a 15% loss

BHP: 525.29 BTRQ: 496.35

 

the initial numbers are obviously way off; we need to wait and see what others post. Also, gears should NOT cause you to have a higher peak HP, that physically makes no sense. The exhaust is already a 2.5in system, and the headers appear better flowing than the 3v 4.6. I bet that flowmaster system gained nothing, and it all had to do with the car and temp. I know I lose a ton of power after driving hard in teh 100 degree heat for 20 minutes.

 

he wasnt claiming the gears added HP, simply shifted the HP to the left in the power band so that the stock HP peak would be hit sooner than it would without the gears and thus the reason for the difference in the numbers, if the stock peak power is after the rev limiter hits then the base run would never show the peak power because the car is being shut down, but with the gears you will reach the peak HP at a lower RPM and could very well see those numbers before the rev limiter kicks in and this could be the reason for the huge difference in numbers, there is no doubt the heat and humidity also played a factor here. Id like to see more dynoed so we can compare, it looks promising and I think we will all be happy when the numbers finally come in.

 

Well, at least this guy is experimenting (if not exactly following the scientific method...) while people with self-control are following proper break-in procedure.

 

I hessitate to get into this but . . . . here goes. rrobello, that statement is simply not true. With lower gears (ie numerically higher), you will reach the peak HP at a lower MPH. The RPM that the engine reaches peak torque and hp remains the same.

The Boss Hog

 

I saw the numbers, it seems that those are very low torque numbers for a 5.4L supercharged motor. I have an 03 Cobra that only has a pulley, catback, and cai and my car made 475 lbs torque at the rear wheels and 448 rwhp.

 

ok well then I dont completely understand how they work. I do know that it will get to the peak HP at a lower MPH and also keep you from reaching higher speeds because the RPMs will be too high, is this only because you are going through the RPMs faster?

 

rrobello,
It is no crime to be a little confused. We all are from time to time. But I really don't know where to start because I don't know exactly where you are confused. Try this:

The rear end gear is a speed reduction gear. It trades speed for actual torque applied to the road. For any given tranny gear, the lower the rear end gear, the higher the acceleration and the lower the mph. Other than contributing to the parasitic losses of the drive line, the gears do not effect the actual output of the engine, but they do effect the performance of the car as stated above.

I sincerly hope that helps at least a little.

The Boss Hog

 

ok but here is the (stupid) question, does it make the car faster by simply going through the RPMs faster or does it actually shift where the car is reaching its peak power and torque to a lower RPM. I was looking at some dyno charts of runs with just changing the gears and it seemed that the lower gears hit the peak power sooner in the RPM range than the higher gears, not by much in most cases but it did move from what I could tell in the charts.

That wasnt so painful was it? I dont know why you thought it was gonna be such a hassel mentioning this....lol!!!

 

It (lower rear end gears) makes the car accelerate faster by providing more torque multiplication between the flywheel and the road. This is the same reason why the car accelerates faster in 1st gear than it does in 4th gear.

I really don’t know what charts you were looking at, but if it is an apples-to-apples comparison, the torque and hp peaks will remain at the same rpm.

I stand corrected.

The Boss Hog

 

Are there any pics of the GT500 exhaust manifolds? I was looking at them on the car Ford had here a few weeks back and from the top they look worse than what's on the S197 GT. At least our's appear to be a semi-shorty header, the GT500's look like logs - reminded me of what came on the 96GT I had. Just curious. As usual, I'm probably way off base but wanted to be sure.

 

Or, maybe he was on the grassy knoll, and HE SHOT KENNEDY!

Come on, this guy is good enough to modify his new GT500 and take the time to share the results, and we're accusing him and/or criticizing him already? These are the first non-magazine numbers we have seen, and I am grateful that he took the time.