My first upgrade

For my first upgrade on my new 98 gp gt I ordered a pair of mufflers with 4 inch in diameter. I've heard it and it sounds nice but how much power will I gain??

For my first upgrade on my new 98 gp gt I ordered a pair of mufflers with 4 inch in diameter. I've heard it and it sounds nice but how much power will I gain??

4" wow. What diameter is the pipe going in and out of the mufflers?

I have heard that if you do not have that much air flowing out of the combustion chamber(a.k.a. your engine producing a heck of exausht pressure) the engine will deflate too quickly even on intake and instead of making more power you might loose some. I have not seen a GP with 4" exhaust before so tell me how your behaves...

:screwy: :screwy: 4" exhaust? i got that on my 41ft boat with twin 455s. something does not sound right, maybe i should put some coffee can exhaust(the big fat muffs out the back) on my boat. the boys and girls at the marina would love that.... :screwy: :screwy:

Maybe he means 4" tip'd mufflers.

He said Mufflers not the entire exhaust was that big

If he is talking about the muffler tips, then he won't be gaining a bit. just a little growl...

Tips are for nothing but looks and mufflers are just for sound. Doubt there are any gains by just replacing the mufflers.

Well first of all its 4 inches in diameter and also Its not a tip its a muffler with a tip and here it is:
http://www.mps-shop.com/PickupSuvs/product.asp?mscssid=DUMMY397LFT48ME6QXWVD5GDLGK78T X1&pf%5Fid=453&dept%5Fid=4280

tell me what you think. I'm hopping for something like 5hp.

Tip doesnt look to bad at all. Should fillthe bumper cutout good.

It says 4" Tip but doesnt say what the inlet size of the muffler is.

Ripn12s, you are correct.
Behvah78, since it only changes the exhaust tip with the muffler the same turbulance you had before reaching the muffler on the whole exhaust system from the exhaust manifold will stay basically the same. If you gain something would not be close even to a 1hp, but should sound nice.

Shoot I should have bought the cut-out then. Too bad it is illegal.

Shoot I should have bought the cut-out then. Too bad it is illegal.

I got a cutout right before the Ypipe and it sounds like butt. It also did not give me better times after MANY tests.

I gained .2 w/ a cutout placed in the same spot.

Gaining a few more hp on my gt seems impossible then! If cut-out doesn't do it then what does?? How about these guyz:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33597&item=2458142011
22hp is definetly bullshit but howabout 5 or somethin

I'd stay away from that ebay crap.

Just stick with either a DHP PCM or CYA Racing PCM

CYA seems to have a good price for what they have. Have you tried it? is it hard to install??

I have both PCM's and have been very happy w/ both.

Cya is the newer pcm and is not as widely used or proven as the DHP.

Install takes maybe 15minutes

Is there a programer for GPGT?? Would the dealership reprogram my ECU if I tell them that I don't want to warranty??

I have heard that if you do not have that much air flowing out of the combustion chamber(a.k.a. your engine producing a heck of exausht pressure) the engine will deflate too quickly even on intake and instead of making more power you might loose some.

If there's not enough back-preasure the end result can be a loss in low-end torque. This may or may not be offset by a relatively equal increase in horsepower throughout the higher RPM range. Thats why some people with stock setups in their V8 trucks or even Camaro's feel they lose a bit off the line after switching to a 4" or even 3" exhaust.

This seems to be the engineering behind the 80 series Flowmaster - aparently it has been proven to provide the most HP gains to stock or lightly modified F-Bodies. Both the 2.5" & 3" inlet models have dual 2.5" outlets. Sounds like peanuts compared to the stock 2.5" (I think) inlet to dual 2.25" outlet but there's actually some decent HP gains to be had.

Both DHP and CYA have PCM versions for the GP GT's