# Stock Exhaust Size



## Agenthol302 (May 18, 2011)

doing a muffler swap and res delete so i need to know what size muffler inlet and outlet to get and what size pipe for res delete any help would be awesome

TIA! :cheers


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## GuatoLT1 (Jul 22, 2009)

2 1/2 all the way to the muffler and the outlet is 3 inch


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## Agenthol302 (May 18, 2011)

so 2 1/2" pipe for res delete and a 2 1/2" in 3" out muffler


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## svede1212 (Nov 1, 2005)

Great. another poster that has us guess the year. . .:confused


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## Agenthol302 (May 18, 2011)

svede1212 said:


> Great. another poster that has us guess the year. . .:confused


**** noob mistake hahah 2004 Auto


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## GuatoLT1 (Jul 22, 2009)

Did the 04 have resinators? Cause ive seen a diagram of the exhaust and didnt see any resinator.


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## Agenthol302 (May 18, 2011)

GuatoLT1 said:


> Did the 04 have resinators? Cause ive seen a diagram of the exhaust and didnt see any resinator.


pretty sure there are 2


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## svede1212 (Nov 1, 2005)

Nope. The '04 didn't have anything that made resin. They do have 2 resonators though. The reason it's important to list what you have (or have it in your sig) when you ask any question is that there are differences. The '04s had 2¼" pipes on it. The '05-'06s had 2½" ones


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## danfigg (Sep 27, 2009)

*re*

looks like the 04 exhaust is less restrictive than the 05-06 to bad they didnt just bring it dual out the back from the very begining doesnt look hard to do with the 04 exhaust----danfigg


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## svede1212 (Nov 1, 2005)

I don't see anything wrong with a one sided dual exhaust. It's been a long time since a split dual con noted a muscle car. Every V6 Grand Am, G6 and Toyota it. The whole scoop, split exhaust thing is so over done as to be ridiculous


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## danfigg (Sep 27, 2009)

*re*

dual exhaust is ment to send exhaust to the rear of the car with as little bends as possible and exit in a manner that is most appealing to give any specific car an attractive look. There is nothing attractive about dual exhaust exiting on the same side. Dual exhaust is the path of least resistance i mean restrictions. Judging by the picture of the undercarrage of the 04 GTO you can see where alot of bends could have been eliminated. Also the wrong muffler style was used. The should have used a center inlet /offset outlet style muffler and that would have made the transition easier for the dual exit to the rear. ANYONE that looks at that picture would know what im talking about. Dual exhaust in definately not ridiculous. Its only ridiculous if you dont have it. ---danfigg


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## pocketmaster (Feb 26, 2010)

danfigg said:


> dual exhaust is ment to send exhaust to the rear of the car with as little bends as possible and exit in a manner that is most appealing to give any specific car an attractive look. There is nothing attractive about dual exhaust exiting on the same side. Dual exhaust is the path of least resistance i mean restrictions. Judging by the picture of the undercarrage of the 04 GTO you can see where alot of bends could have been eliminated. Also the wrong muffler style was used. The should have used a center inlet /offset outlet style muffler and that would have made the transition easier for the dual exit to the rear. ANYONE that looks at that picture would know what im talking about. Dual exhaust in definately not ridiculous. Its only ridiculous if you dont have it. ---danfigg


Simmer down pot roast!!! I have an 05, M6 X-pipe w/ muffler delete. I see your point. I assume this is the reason aftermarket headers are more efficient than the stock headers ??


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## svede1212 (Nov 1, 2005)

pocketmaster said:


> Simmer down pot roast!!! I have an 05, M6 X-pipe w/ muffler delete. I see your point. I assume this is the reason aftermarket headers are more efficient than the stock headers ??


The reason headers are more efficient is the length and diameter of the primaries (the single pipe from each cylinder) to the common point of connection. Exhaust is not a continuous flow of gas. It is a series of pulses and pressure waves. When gas travels in a pulse that's suddenly shut off at one end the mass can not stop and thus it creates a partial vacuum behind it. If that vacuum is timed through the pipe length to coincide with the pressure wave of an adjacent pipe it helps to pull or "scavenge" the gases out. An X-pipe helps to do the same thing. Because of that the displacement of the engine, primary diameter as well as the length have a specific RPM that it's most efficient at just like tuning a bass speaker. That's a simple explanation as pressure waves are traveling both up and down the exhaust and for that matter the intake. Remember that sound is pressure waves and you can hear the engine out the TB so you know that pressure travels out as well as into the engine in both intake and exhaust. Exhaust in general is one of the least understood in that it seems so simple yet some of it is counter intuitive. 

I have a Grand Prix and a G6 GTP both with split exhaust out a common muffler. They both don't stand a chance against the "plain" goat. Here in the U.S. the split dual is venerated yet in most of the world it isn't seen as such a big deal. Holden, BMW and a lot of other makers use same side exhaust. When this car came over they didn't understand we want our split exhausts and hood scoops or we didn't have performance car! FWIW the '04 uses 2 different muffler types to deliver the most authentic 60's muscle car sound of any modern car. GM spent more time of that than almost anything on the car to bring it over here. They shipped an old school GTO to Oz and spent countless hours computer analyzing the sound to match it.

Here we also have the ricer mentality of large exhaust tips. They are actually counter to a good exhaust design. The tips should be of the same size or smaller than the rest of the the system. As the gases travel the length of the pipe it cools considerably. As gases cool they shrink in volume. If the pipe remains the same size the gases slow down due to that shrinkage. A perfectly designed system would have a pipe size that gave the highest velocity with lowest back pressure. The largest pipe size would be at the beginning and taper back so that at the exhaust it was the smallest. That way the gases would maintain the same high velocity from beginning to end. Big tips do the opposite.:willy:


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## Agenthol302 (May 18, 2011)

svede1212 said:


> Nope. The '04 didn't have anything that made resin. They do have 2 resonators though. The reason it's important to list what you have (or have it in your sig) when you ask any question is that there are differences. The '04s had 2¼" pipes on it. The '05-'06s had 2½" ones


yea i know i have a camaro so i dont put a sig in the gto is my dads i just forgot haha i usually have all the info in the sig...but thanks for the info i will post up pics and what not when we start making the exhaust arty:


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## danfigg (Sep 27, 2009)

*re*

Old school glass packs spintech X-pipe and study this picture to figure out how you would route it. I think it would sound good and not to expensive if you have a good mechanic that can bend the pipes for you---danfigg


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