what size exhuast piping?

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what size exhuast piping?

Postby Cormudgen » Mon Oct 18, 2004 7:26 pm

What size exhaust piping do you have going to the rear of the car. When I bought this car it came with a 3" pipe going into a Flowmaster muffler. Occasionaly when you hit a bump the exhuast pipe bumps intto somthin under the chasis right near the rear diff. I though an exhaust hanger may have broken loose or something to that like. So I took it to the an exhaust shop that had a lift and we checked it out underneath. No hangers were broken and he said that none needed to be added, in fact min had one more than was really needed. He said that the 3" was really too big. He recomended I go down to a 2".

I'm considering going down to a 2 or 2.5". Also what mufflers are you using? I don't really like the sound of my current one at all and am considering gettin an Apexi N1.
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Postby RIalltrac » Mon Oct 18, 2004 7:39 pm

I want to say stock pipe size is 2.25, so going down to 2 inch would be pointless, 2.5 inch isnt a bad size but what are your overall goals for the car. There comes a point when that may be a bottleneck and if your like me and dont like buying things twice you might want to stick with the 3 incher. Its also important as to how the pipe is bent, if it isnt mandrel bent its not going to flow as nicely
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Postby Cormudgen » Mon Oct 18, 2004 8:11 pm

RIalltrac wrote:I want to say stock pipe size is 2.25, so going down to 2 inch would be pointless, 2.5 inch isnt a bad size but what are your overall goals for the car. There comes a point when that may be a bottleneck and if your like me and dont like buying things twice you might want to stick with the 3 incher. Its also important as to how the pipe is bent, if it isnt mandrel bent its not going to flow as nicely


I hve no idea of how the piping is bent( as in mandrel). How would I tell. I guess that is good to know that the 3" is a good thing. I dont think I will ever go past the 330 mark at the wheels.

The noise it makes when it hits is extremely annoying. I guess I should try taping some padding to what it is hitting. I cant think of anything that will soften the bumping noise and not be affected by the exhaus pipes heat though. I guess another option is to have another exhaust made with a different route. Anyone have pictures of the way their exhaust is routed? I wish I would have my digital cam so I could have taken pics while I was up under there.

Mark
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Postby alltracman78 » Mon Oct 18, 2004 8:36 pm

Whoever told you 2" on a turbo car is a idiot.
2 1/2 is the min you should go.
As far as routing, it should go straight back, 'til it gets to the rearend, which it goes over, and exits next to the gas tank.

*It actually goes over the pass side rear cv shaft.*
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Postby MrWOT » Mon Oct 18, 2004 9:51 pm

I'm going to use a 2 1/2 inch system, with 3" diameter wherever there are bends, since the radius will decrease when the bend is made, mandrel or not. I've sourced several places and books that all insist that 2 1/2 should be just fine for up to ~400hp. 3" is fine and probly better if you want to raise rev limit to around 8k or higher. I'm sticking with near stock redline. 6500 for me, for reasons of durability and the compressor I'm having fabbed, for higher redline you really need more labor too, like headwork and probly intake manifold and to really take advantage of it. I don't trust high rpm without at least doing the shimless bucket conversion.
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Postby Gary » Mon Oct 18, 2004 10:52 pm

MrWOT wrote:I'm going to use a 2 1/2 inch system, with 3" diameter wherever there are bends, since the radius will decrease when the bend is made, mandrel or not.

I don't get it.
Mandrel bent pipe should have the same diameter along the bend.
Cormudgen wrote:I hve no idea of how the piping is bent( as in mandrel). How would I tell.

Here are a pic of mandrel bend (bottom) and non mandrel bend (top).

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Postby Stubble » Tue Oct 19, 2004 12:00 am

Sweet picture. The one in my manufacturing engineering textbook isn't as good as that.
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Postby MrWOT » Tue Oct 19, 2004 12:31 am

Gary: Even a mandrel bend loses some diameter, I've talked to several shops and checked myself, on a GOOD mandrel bend you will lose about 1/8", I've seen losses of almost 1/2" though on some 'mandrel bent' aftermarket systems (magnaflow, and walker to name 2) :shock: . All mandrel benders are NOT created or used equal.

I'm going with the 3" sections for the large bends, but that's still up in the air since I will pick a final size after I get a mock-up done. Might go with 2 3/4" depending on how the bends come out.
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Postby Cormudgen » Tue Oct 19, 2004 2:33 am

alltracman78 wrote:Whoever told you 2" on a turbo car is a idiot.
2 1/2 is the min you should go.
As far as routing, it should go straight back, 'til it gets to the rearend, which it goes over, and exits next to the gas tank.

*It actually goes over the pass side rear cv shaft.*


that sounds exactly where its going.....and right where its hitting
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Postby alltracman78 » Tue Oct 19, 2004 4:59 am

Over the rear? That seems to be where most people have problems. Try to find someone in your area that has a Aussie ex, and look at it. :shrug:
Aussie muffler sounds good. too. :D
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Postby furpo » Tue Oct 19, 2004 8:20 am

ok i don't know 100% what i am talking about so can someone either say im wrong or right.

a mandrill is a male that a tube is formed around. this is a fixed size. ie 3 inch. if a bend is formed around a male of x diameter it can not be any smaller. i don't understand how it is lossing internal diameter.

roger
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Postby jlcelica » Tue Oct 19, 2004 11:33 am

i had the same problem with my 3inch exhaust , it was rubbing on part of the underbody just past the rear suspension . i figured it could be fixed by adding another exhaust hanger right after it. or you could just wrap that part of the exhaust like 30 times with some exhaust wrap. :shrug:
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the circled area is where mine was hitting the underside of the car.
i recommend magnaflow if you want to something that sounds nice. At 3inches with my magnaflow i think it sounded nice at all rpm ranges. [/img]
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Postby alltracman78 » Tue Oct 19, 2004 11:54 am

Wasn't yours a fwd?
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Postby jlcelica » Tue Oct 19, 2004 1:17 pm

alltracman78 wrote:Wasn't yours a fwd?

and automatic :cry:
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Postby alltracman78 » Tue Oct 19, 2004 1:20 pm

auto's better for draggin', sometimes anyways.
But your exhaust would be different than ours.
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