Exhaust sizing.

[Mopar318]

Im going to be building a down pipe and side exit exhaust. Im stuck between using 2.5" or 3". Im using 409 mandrel bent, and dumping it behind the drivers door. Running no cat, using a dynomax ultra flow.

Car is a 89 daytona 2.2 TII. 12psi, ported TB, and exhaust manifold. Will be running 20psi in the future. I have a 2.5" swinge valve. and 3" is adequate on my turbo Dakota, so im thinking about staying down to 2.5".

Next questions is does anyone know where to get the flange that attached to the swing valve. I may just take off the SV and weld on a V-band assembly depending on if its cast steel or cast iron.

[Captain Chaos]

2.5 is sufficient for a moderate build. However it won't hinder you to use the 3" if you have it readily available though.

[Mopar318]

2.5 is sufficient for a moderate build. However it won't hinder you to use the 3" if you have it readily available though.

I need to order the bends. I get them cheap though and 2.5 and 3 are pretty much the same price. You know if you can get the flange for the SV. I think its a ball/flange type but I havnt really looked at it.

[89daytonacs]

you don't mean the donut do you

[turbovanman²]

I would go 3 inch.

[Mopar318]

you don't mean the donut do you

What ever is used to attach the down pipe to the SV. I have not had a chance to really look at it.

[Captain Chaos]

What ever is used to attach the down pipe to the SV. I have not had a chance to really look at it.

I got mine from TU for the 3". If you have a good NAPA guy you can take your 2.5 up there and go through the catalog and find th eproper 3".

[contraption22]

I would go 3". There will be no detrimental effects going larger on mild build, but it will allow room to grow if you decide to upgrade later.

[Mopar318]

I got mine from TU for the 3". If you have a good NAPA guy you can take your 2.5 up there and go through the catalog and find th eproper 3".

So you got a donut with a 3" pipe to to fit the stock swing valve correct? How much was that? I could weld on a reducer but I like the idea of everything being new when im fabbing something, and i hate welding on old metal, especially with a tig.

Can some one post a picture of the factory SW I looked around but couldnt find any pictures, and Im pretty busy with work right now so i dont get much play time. It will help me decide if I wanna weld on a V-band flang or not.

[moparzrule]

3'' will spool the turbo faster, even on a stock setup.

[Mopar318]

3'' will spool the turbo faster, even on a stock setup.

It already spools damn quick. Im gonna order the pipe tonight. Should start on this within the next few weeks when i get the weekend off for work. Then I can put a bung in for my wideband, and get some more boost to the bastard.

[Captain Chaos]

Yes, 3" pipe with the 3" donut in 2 1/2" swingvalve fit fine on my Horizon.

[johnl]

I've got 3" but always wondered if it was overboard. Any evidence of clear necessity of 3" to make big power?

[moparzrule]

I've got 3" but always wondered if it was overboard. Any evidence of clear necessity of 3" to make big power?

A 3'' system has been dyno proven to gain power over a 2.5'' on even less than 300 WHP setups.

[mario03SRT]

The LESS restriction the better. Remember you are driving a glorified air pump that will operated much better with NO backpressure on the turbine.

Weight, fit, and expense do play a part in the decision.

[Mopar318]

I love having my own bussiness, acounts with suppliers are nice. Just got all the materials to do the downpipe, and exhaust, in mandrel bent 304 stainless tubing for 65 bucks.