Freefallin

My stock exhaust is all shot and is in need of replacement. Car is an 04 GTO.

The following are my options:

1) 3" dual straight pipe.

2) 3" dual single muffler

3) 3" dual 2 mufflers

4) 3" x pipe (no muffler/s)

5) 3" x pipe single muffler

6) 3" x pipe 2 mufflers

7) 2.5" dual straight pipe.

8) 2.5" dual single muffler

9) 2.5" dual 2 mufflers

10) 2.5" x pipe (no muffler/s)

11) 2.5" x pipe single muffler

12) 2.5" x pipe 2 mufflers

13) Other (your suggestion)

All of them will cost me the same (very cheap).

Mind you, this will be on a bone stock ls1. Only mode is 1 3/8 LT.

First priority is performance, low end torque being crucial for drag.

Sound/loudness is not an issue as long as it doesn't sound like poop.

I'm not going out of my way to do this. I'm doing it cz I have to replace the exhaust anyway.
So I'm not doing this expecting huge gains. If 1HP is all I will gain after all is said and done...I'm satisfied. This is costing me peanuts so its all good.

Which option should I go for?

HCI2000SS

iTrader: (2)

Duals with x - pipe sounds good to me

Freefallin

4 or 10?

HCI2000SS

iTrader: (2)

I like 4 better

Rise of the Phoenix

iTrader: (27)

4 for sure.

Freefallin

So you guys don't think 3" is a bit too much ( counterproductive) for a stock ls1?

What about what is said that 3" not producing enough back pressure, thus killing torque?

MuhThugga

lol...dual 3" exhaust on a stock LS1 without any mufflers

Is this your daily? Because that will get tiresome before you even make it home from the exhaust shop.

Fry_

I'm hoping this is a typo, I think stock manifolds would be better than 1 3/8's headers.

Also I'd go with #6 with bullet mufflers.

DREAMZ28

iTrader: (1)

Typical misconception is you need back pressure in the exhaust to create low end torque. The opposite is true. The better flowing the better the torque production across the board, from the better scavenging of the cylinder.

Note I said better flowing not bigger.

Also if you're looking at being faster at the track, focus on your torque production at mid and high range not low end. Unless you shift at 3500, low end torque is almost irrelevant at the strip. Mid and high is what you want.

Now if this car is a daily, you're not gonna wanna be rolling around on 3" x pipe with no mufflers. At least put bullets on. Doesn't sound like this is a dedicated drag car, more like a street car you want the most out of.

Pharcyde50

iTrader: (11)

3" duals x pipe and muffler of choice! Bullets are gonna be loud for a daily

CBM Motorsports

iTrader: (2)

Besides for the performance aspect of this, I would consider the rear bumper. Do you have the original rear bumper? If so you only have the exit on one side. Might be hard to fit 2 3" out the spot. If you have the one off the 05-06 it would look funny with just one exhaust pipe. Just something to think about!

BTW I would do 3" single. Sounds great.

Freefallin

So all of you are saying 3", with x pipe... Why x pipe and not straight?

Fry_

Because straight pipes are for redneck farm trucks.

Seriously though a x pipe produced a scavenging effect that improves performance.

Freefallin

Aha. Any brand/model suggestions?

dr_whigham

iTrader: (49)

I vote #6

Freefallin

Alright, just to confirm, you guys don't think a dual 3" x pipe is too big for a stock 5.7 in a sense that it will be counterproductive, correct?

I'm sorry, its just that it seems to contradict what many (other) ppl are saying, including the exhaust shop! Went in yesterday to have them make a 3" x pipe and the guy was like that's going to be too big for your engine. So I dropped it to run it by here, again.

Obviously a lot of you here know way more than I do when it comes to this so honestly, I'm just going to go with whatever is most suggested on this thread.

So yeah...drop some knowledge folks!

S_M_I_D_D_Y

single 3.5 sounds tuff as ****. and will flow more than 2.5 twin but not quite as much as twin 3 which can kill lowdown torque on a stockish size non boosted motor.

Freefallin

See stuff like that is what I keep hearing, and then you got people like DREAMZ28 that say nah! thats just a misconception and that it would actually increase torque!

Fry_

That because people are stubborn and set in there ways or believe things that they have been told about 70's and 80's SBC 350's that only made 200hp. 3" duals aren't to big for a LS1. Lets face it these same people would probably say 1 7/8's or even 1 3/4 headers are to big for a stock 5.7 and that you should run 1 5/8's but we all know that's not true.

thunderstruck507

iTrader: (18)

3" duals is not too big...damn why won't these myths die? And on a GTO going from stock to a y pipe of any sort is ludicrous and a step backward.

Dual 3" with or without an X and a muffler for each side. Done.

If you are really that worried about it, do 2.5" duals but you are leaving power on the table if you do more mods in the future.