exhaust... again

[gunnervirus]

Sorry to keep bugging everyone, but I have yet another question. A full 3 inch exhaust is going to cost a bit more than a 2.5 inch. If I have a 2.5" downpipe, will it make a difference if the piping behind it is 3"? A 3" cat costs a lot more than a 2.5" cat. I'm trying to figure everything out before I take the car down to the exhaust shop.

Thanks again,

Ben

 

[Ttype83]

go with the 3" single shot..it's alittle more($225).
Now the down pipe is very important, to get the most out of it it needs to be mandrel bent. It doesn't get smaller in the bents.
It will feed into the 3", but the 3" will drop to 2 1/2" at the bents.

Are you going to use dynomax(sp?) mufflers?

 

[gunnervirus]

Jim,

Yeah, I'm going to go with the Dynomax muffler. There aren't any shops nearby that have a mandrel pipe bender so I'm stuck with the old crush bent pipes. Engine conpartment size has limited me to a 2.5" downpipe, and a crossover that snakes all over the place

At least I'll have a little more low-end torque...

Ben

 

[b4black]

First, will a 3" DP even connect to the turbo's elbow? The stock DP's are 2" or 2.25" with plenty of kinks and tight spots.

I think if you look at the SFI/IC cars, a 2.5" DP will take a car pretty far. I'm not sure a carb/turbo could take advantage of a 3" over a 2.5". If the DP is 2.5", then I don't think it would help to run a 3" cat and cat-back.



I would have a port or bung made into the DP so you could hook up a gauge and measure backpressure. Put another one on the up-pipe and measure the pre-turbo back pressure as well.


I bought a Terry Houston DP a couple of weeks ago. Of course it won't fit our cars, but it was only $25 and in like new condition (they go for $400+ new). 3" stainless, mandral bent, intergal elbow and internal (stock style) wastegate. That's what we need.

Actually a 2.5" mandral bent DP that could be welded to the stock elbow and then port the elbow would be great.

 

[Scott Adcock]

I'm not sure that a 3" DP will help that much either. I had a custom 2.5" DP made for my car, all madrel bent, and with all the other mods, tube headers, cam, cold air intake, 2.5" cat and dual exhaust, etc, etc,. The car did run better but I don't think that increasing the DP to 3"would net any more positive gains.

 

[Ttype83]

Originally posted by Scott Adcock
The car did run better but I don't think that increasing the DP to 3"would net any more positive gains.

You & Rich are right, our cars will not take advantage of the 3" DP, Only cars running 10's or faster need a 3" DP. A 2 1/2" is all we will need with a good cross over.
Jim