I tried to search alittle bit but had little luck, but I am trying to find a 65mm catback exhaust with no bottlenecks to put on my R. Which ones have these specs? I just need as many as you can think of so I can investigate each one. The more choices the better. I am planning on mounting it with a carsound cat and a Toda header. Thanx for the info.

 

SMSP.........

 

SMSP and HyTech are both 2.5" with no bottlenecks. Type One is also 2.5" but I believe has or used to have bottlenecks, I heard they came out with a newer version that doesn't though. They would go perfect with a 2.5" header.

 

FYI. 2.5" = 2.5 * 25.4 = 63.5 mm
I believe a 2.5" OD header is actually 65 mm OD not 63.5 mm OD

 

My DC JDM was 2.5" OD. I think the Toda header is 2.5" (63.5mm) OD also, since it is 60mm ID collector and figuring it uses the standard 16-gauge steel it would about about a 1.5mm wall thickness.

 

Hmmm, strange. Because the OEM JDM 4-1 has a 65mm OD collector. Not 63.5 mm.....

 

Wouldn't it need a bigger doughnut gasket then? The S2000 doughnut that I used for my DC JDM header was 2.5" ID. But I don't know that was so long ago and I don't even have the header anymore so I can't go check to be sure.

 

If the Toda and most other JDM ITR header are 63mm OD (60mm ID), then why would ppl need a 65mm OD exhaust to go with it? Won't the 60mm ID that 99% of the JDM exhaust company offered will make it a perfect match already?

 

Those exhausts are 60mm OD. The actual ID is about 2.25"

 

I believe all JDM headers have a collector of 65 mm OD, because they use the metric system in Japan. In the US everyone call it 2.5" because it's approx. 2.5", but it is actually 2.559"

SMSP, can you confirm this?

And don't forget that this only applies for the part of the collector where the donut sits. The collector is usually 60 mm OD at the spot where the O2 bung is...




[Modified by DutchITR1689, 9:25 PM 3/9/2003]

 

Some JDM exhausts has 60.5mm OD and only 1mm piping thickness, so the ID is around 58.5 mm, I guess that isn't too bad.