I have jdm 4-1 + carsound + stock catback. How much difference would i get for that particular mod?
What other bottleneck is in the stock catback?

SMSP, can you IM me the price for that single piece?

 

I've heard that if you're only going to MILDLY mod your car then this setup is good. But eventually your car would want to fart more and you'll need to change out the stock catback to a full 2.5" one.

The stock exhaust is good for intake/headers and maybe cams.

 

bottlenecks are in the b-pipe at the cat flange and another right near the muffler.

 

Price in Sept 2001 was $40 for mild steel or $55 for stainless.

Bill

 

holy...that's pretty steep for that small piece of metal....
is it custom weld by smsp
or do you think i can get some generic one at a muffler shop?

 

The mild steel one is mig welded while the stainless one is tig welded. I never dyno'd the the before and after on a stock ITR exhaust. I installed one of the mild steel 2-1/2" ID x 2-3/8" OD adapters on Jason's (Vader, or who knows what name he's using today) ITR with a Toda header, 2-1/2" cat and Tanabe RM which has a bottle neck with an ID of 1-7/8" (Stock ITR is 1-3/4") and a CAI. He picked up 4 whp from 6000-8500 and got a really nice bump from 3800-4800. Since he tested it for me I didn't charge him anything but $40 + labor for 4 whp over 2500 rpm is about as good as you are going to get.

Here's the 2-1/2" ID x 2-3/8" OD stainless adapter

Here's the before and after of Jason's Tanabe, notice the exhaust deposits on the Tanabe B pipe flange, this was after 2 weeks of driving I believe.

This is what you'll have if you leave the stock B pipe alone



[Modified by SMSP, 11:15 PM 5/17/2002]

 

Mabe I am tired of just stupid but is this flange to adapt a 2.5 cat to a 2.25 cat back system more efficently I mean it lets the exaust gases go from big to small with out causing so mutch back pressure witch improves flow?

 

It's not ideal but it's better than not removing the bottleneck. Ideal setup is a full 65 mm OD (not 2.5") system. The JDM ITR 4-1 has a 65mm OD flange. I don't know why the DC JDM has a 2.5" (63mm) flange.
I assume all the other JDM headers (like spoon, mugen, Toda) have 65 mm OD flange....

 

I believe the DC JDM has a 65mm collector. I say this because I used to send 2-1/2" donuts to folks with these headers and they told me it wouldn't go on so now I always send them the JDM donut and it fits fine.

 

Yeah on the DC JDM the pipe that the donut fits over is 65mm, but the collector where the 4 pipes meet and the O2 sensor is very slightly narrower (possibly 63mm didn't measure).


[Modified by HardHead42, 11:53 PM 8/1/2002]

 

I've measured that, it's 60 mm...

 

you can get those reducers from summitracing.com for like $20 ish