Exhaust sizes GT

[opelnut_1]

I am trying to figure out what size exhaust will fit in the Gt. Bob has recommended 2.5 for my application.

Is there anybody running this size in their Gt? I am wondering about clearance over the axle. and Ground clearance, my application has the sport spring up front an the progressive lenk springs in the rear.

The other idea I had was to run square or oval exhaust to help with the ground clearance.


anybody????

[namba209]

Rick, I'm running true dual 2.5" exhaust on Willit? You can check out the pics of it in Phase V of the "Project and Articles" forum, accesed from the box on the left side of the home page. A couple of things to note, I didn't use the cavity in the floor pan to locate the muffler on the pax side of the car. You could with yours and gain additional ground clearance. I have to be careful going over speed bumps because mine is down lower than a stock setup and the down tubes need to be shortened a bit yet. HTH.

[Lindsay]

Stock GT:
2" all the way back, and 2.5" over the axle.

But, you may have more than a stock engine?

[opelnut_1]

What if instead of running a single 2.5 pipe from the y in the downpipe. You cut out the y and ran the two 1 7/8 pipe all the way back? It could exit where the resonator tips did. this would allow pleanty of room over axle and could be spaced further away from body with out effecting ground clearence.


Rally Bob would this effect performance? would probably run it through 2 in 2 out muffler. and maybe an h pipe config to balance out the tone.

http://www.opelgt.com/photos//data/500/P1030974.JPG

[RallyBob]

Originally Posted by opelnut_1 What if instead of running a single 2.5 pipe from the y in the downpipe. You cut out the y and ran the two 1 7/8 pipe all the way back? It could exit where the resinator tips did. this would allow pleanty of room over axle and could be spaced further away from body with out effecting ground clearence. Rally Bob would this effect performance? would probably run it through 2 in 2 out muffler.

This will absolutely kill performance. Gotta merge the two downpipes into one pipe for an inline 4-cylinder, or you effectively kill the scavenging.

A better idea would be to 'crush' the 2.5" tubing into an oval shape if you want ground clearance.

Bob

[opelnut_1]

Originally Posted by RallyBob A better idea would be to 'crush' the 2.5" tubing into an oval shape if you want ground clearance. Bob

what about running retangular say 1.5 by 3.5 exhaust?

[RallyBob]

Originally Posted by opelnut_1 what about running retangular say 1.5 by 3.5 exhaust?

Sure, that's within 5% of the area of a 2.5" round tube.

Bob

[Paul]

Originally Posted by opelnut_1 what about running retangular say 1.5 by 3.5 exhaust?

Wouldn't this be kinda hard to bend at typical muffler shop?

[RallyBob]

Originally Posted by Paul Wouldn't this be kinda hard to bend at typical muffler shop?

You think that's tough, try finding a muffler to fit that size tubing!

[jtb]

Hey, where is Captain Spell-check? Nobody has corrected the spelling of exhaust yet (exaust).

Well, I'm running 2.25" exhaust front to back, but nothing is stock so I'm not sure how much this will help you.

In the picture you can (kind of) see that I built a recess behind the passenger's seat to accommodate the resonator. This is hidden under the rear platform of the interior. Then the pipe goes up over the moustache bar (again, not Opel). I was considering 'ovalizing' the pipe, but as it turned out, it fit (barely). I would think you should have enough room in a stock application to go over the axle.
I used stainless, but I didn't make any bends, I just bought a couple of pre-bent pieces, chopped them up and welded them back together to form the shape. These pre-bent things are available in regular exhaust tube, too.

HTH,

jtb

[kent]

Originally Posted by RallyBob This will absolutely kill performance. Gotta merge the two downpipes into one pipe for an inline 4-cylinder, or you effectively kill the scavenging. A better idea would be to 'crush' the 2.5" tubing into an oval shape if you want ground clearance. Bob

Exactly what will this do? This is what was done to my gt by the PO I'm finally getting around to changing it after 3+ years and wondering what to expect? Hmm I tried to copy the whole post but only got Bob's quote how do you get both? see post #5

[GTJIM]

Originally Posted by kent Exactly what will this do?

Keeping the pipes divided after the exhaust manifold prevents the 'tuning' effect of a correctly connected system. Mainly it reduces the torque in the mid-range and 'clips' the top out of the horsepower curve.

So the car will both accelerate slower and reach a lower top speed.

The sound of the exhaust note becomes 'flatter' and more like a pair of twin cylinder motors; rather than a purring four!