The 98+ JDM 2.5" header collector. Thats 2.5" outside diameter inside is more like 2.25 it seems? Anyways there is that donut thing around it made out of woven steel or something IDK. But it tapers from like a 3" or so to a 2.6"? Rough estimates here but what size opening for a cat do I get then? Do I get one to fit over that donut thing or one that fits up against it? Thanks

 

U will need a 2.5 donut gasket and a 2.5 cat or test pipe (2.5 opening that is). The Donut gasket kinda sits against the opening of the cat or test pipe, doesnt really go all the way inside, and forms the seal.

 

what is the woven steel or w/e donut on the header collector? So i need to find a rubber one too?

 

Basically you have the header, the gasket, and the cat or test pipe. The gasket is sort of like metal or graphite material. The gasket will slip over the tip of the header collector, and the tapered part will form the seal up against the cat or test pipe opening.

I used a OEM Honda S2000 gasket on my JDM header. There is no "rubber one" that I know of, just one metal gasket shaped like a tapered donut. You could also get these at any auto parts store, just as for a header collector donut gasket for an S2000 or 2.5 inch gasket.

 

Oh well I already have that so all i need I guess is a 2.5" cat. Now what on to use, test pipes are a little too raspy IMO.

 

Make sure you check the length of cat or test pipe you need before you buy one, the JDM header has a longer collector that the USDM one and if you are using a USDM lenght exhasut system, you will need a cat or test pipe that is shorter than the USDM length.

 

good bit of info, thanks. I will have to see how much of a gap is there with the JDM header and USDM piping. Worst case scenario is I have to get the exhaust piping cut and the flange welded back on to fit the cat. I want to go with a new high flow catalytic.

 

i am in the same exact situation, except its on a ej8.

Can you guys recommend a good/cheap 2.5 inch high-flow cat? and where to buy from?

Another question... ive read great things about the Apexi ws2 exhaust, but there is no 2.5 inch im all about having a nice quiet exhaust, and it seems the ws2 is the best.

What is better performance wise? Getting a custom 2.5 inch exhaust made to a Universal 3 inch WS2 or a 2.25 inch Ws2?

Thanks.

 

bump. anyone?

 

Well I believe the WS2 is a chambered muffler, like OEM, so in my opnion is its somewhat pointless using this muffler with a large diameter exahust piping and a test pipe or high flow cat.

If you are going to use a 2.5 collector header, test pipe or high flow cat, and a 2.5 or 3 inch exhaust pipe, I would also use a high flow unchambered muffler.

 

i see, so is there anything that compares in quietness to the ws2?

 

Alright so i'm going with a 2.5" Carsound/Magnaflow Cat (unsure of size an whether to get round or oval), I found 2.5" B piping on EBAY but its not crappy stuff its actually T-304 Stainless and it will be bolting onto my Spoon N1 axle back. Should sound pretty darn good. I'm always getting compliments on the Spoon exhaust note. I also have the quiet tip to put in. I'll probably post up a video.