JDM downpipe.

[JonLGT]

So I was on grupp-s looking for a catback and I noticed the exhaust i want says that it needs a JDM downpipe to mate up to it. Does anybody know where I can purchase a JDM downpipe and what the difference is between the USDM and JDM pipes, thanks.

[StiGuy]

Even though the overall length of the tbe is the same, the individual parts (i.e. dp and cbe) are different lengths. I can't remember which one is which but I think the jdm dp is longer than the Usdm and the cbe is shorter than the Usdm one.

[Frankie Figs]

I'm pretty sure you're right, the JDM DP is longer. Just make sure you dont get a Ver 8-up DP cuz they are twinscroll :)

[Alizarin]

Even though the overall length of the tbe is the same, the individual parts (i.e. dp and cbe) are different lengths. I can't remember which one is which but I think the jdm dp is longer than the Usdm and the cbe is shorter than the Usdm one.

I found this info on NASIOC in the conversions forum, maybe it can help answer. Seems to be related to putting an EJ20 into an RS (GC8). The GG/GD chassis is the bugeye model.
Q: "I'm doing an EJ20 swap, which exhaust should I use?"
A: Until proven otherwise, the exhaust from a standard WRX from 1993-2004 has remained relatively unchanged. This means that if you are performing a swap from an Impreza chassis to an Impreza chassis, you can use any complete WRX exhaust. If you are swapping from an Impreza chassis to a Legacy chassis, then the exhaust must be lengthened to accomodate the longer chassis.

If you are doing a piece-meal exhaust, there are four types of downpipes available from any of the EJ20 equipped cars: the twin-turbo downpipe, a la GTB; the twin-scroll downpipe, a la STi Ver. VIII; the IHI flanged downpipe from a pre-MY01 JDM vehicle or post-MY01 non-JDM vehicle, a la USDM WRX or STi Ver. VI; or finally the IHI flanged downpipe from a post-MY01 JDM vehicle; a la STi Ver VII. The twin-turbo downpipe is only going to work in a RHD car, so this will almost never be used. The twin-scroll downpipe can only be used with an IHI twin-scroll turbo, so this will only be used with some STi Ver. VIII vehicles. The pre-MY01 JDM downpipe is the most common downpipe used with EJ20 vehicles. The post-MY01 JDM downpipe was introduced with the GG/GD chassis and is a few inches shorter than the pre-MY01 downpipe.

If you choose the pre-MY01, then you must mate it with a similar system. It can be mix-matched as long as it is not matched with a post-MY01 JDM system; this includes using cat-backs designed to work with the EJ25 engines. If you choose the post-MY01, then you must mate it with what is commonly referred to as a "JDM cat-back". The flange at the axle was rotated on the GG/GD chassis so the mid-pipe and the axle-back must be from the same chassis generation.

I also found this related to a Zerosports exhaust (is this the one you're considering?)

the zero sports DP will only work with a jdm exhaust. i ordered a fujitsubo super ti exhaust. it should be in on monday.
it has something to do with the length of the pipes. i think the jdm dp is 4" shorted (perhaps since it has no catless) and the jdm exhaust is 4" longer as compared to the usdm one. or it could be the other way around. hehe

so basically u need a jdm dp tp go with a jdm cat back and u need a usdm dp to go with a usdm cat back.

[smooth_ej20]

jdm dp's are longer and cat backs shorter. I have the Cusco which is JDM, i think the JIC and the Invidia also come in JDM flavor but double check with the supplier. BTW which exhaust are you gonna run? as far as places try www.hopupracing.com (http://www.hopupracing.com) www.z1auto.com (http://www.z1auto.com) or www.fizzautosports.com (http://www.fizzautosports.com) one of those 3 should have what you need.