I still have a stock cat and stock exhaust. Since the DC is 2.5 inch I'm guessing I will need some kind of adaptor to bolt it to the cat? If not, what are my options?

 

Your easiest option is to IM SMSP on this board and purchase a new catalytic converter (~$125-$200) which has 2.5" inlet and 2.0" (?) outlet to make everything line-up correctly. You can just get an adaptor make your stock cat work... your JDM header is longer than stock and you'll need a shorter cat.

 

if you want to keep stock size cat and exhaust piping, then get a regular version dc header, sell the jdm one. It pointless to get the 2.5in collector then just restrict it again. so do like i did. get a custom 2.5in car sound cat and bigger ehxuat, my case an apexi world sport cat-back

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SleepnCiViC &raquo;</TD></TR><TR><TD CLASS="quote">if you want to keep stock size cat and exhaust piping, then get a regular version dc header, sell the jdm one. It pointless to get the 2.5in collector then just restrict it again. so do like i did. get a custom 2.5in car sound cat and bigger ehxuat, my case an apexi world sport cat-back</TD></TR></TABLE>

I don't agree w/ this statement (entirely). I do think you'll feel more of a difference w/ this header and a 2.5" exhaust but I think it's still worth getting even w/ the stock exhaust. I ran the JDM DC 4-1 for a while w/ Carsound cat and stock exhaust and was quite pleased.

 

there will be an increase but he will not be gettin the full potential out of the jdm header, jsut in my opinion its a waiste of money, too each his own though

 

Unless your running bigger cams, you really don't need a 2.5" exhaust piping for stock cams.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EM1b18cR &raquo;</TD></TR><TR><TD CLASS="quote">Unless your running bigger cams, you really don't need a 2.5" exhaust piping for stock cams.</TD></TR></TABLE>

There's nothing wrong with 2.5" for stock cams.

 

Thanks for the info. I want to do it properly so I guess I'll need to pick up another cat.

 

yeah best bet is to replace that, go with a test pipe heehee

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DannyITR &raquo;</TD></TR><TR><TD CLASS="quote">Thanks for the info. I want to do it properly so I guess I'll need to pick up another cat. </TD></TR></TABLE>

Don't forget a 2.5"-&gt;2.25" tapered reducer to eliminate the first bottleneck in the OEM exhaust. You'll want to remove this bottleneck if you'll be keeping the stock exhaust.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EM1b18cR &raquo;</TD></TR><TR><TD CLASS="quote">Unless your running bigger cams, you really don't need a 2.5" exhaust piping for stock cams.</TD></TR></TABLE>

Ahhh, why post if you don't know what you're talking about? The R thrives on a 2.5" exhaust system...look it up man....here's a hint...Hytech and SMSP.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

Don't forget a 2.5"-&gt;2.25" tapered reducer to eliminate the first bottleneck in the OEM exhaust. You'll want to remove this bottleneck if you'll be keeping the stock exhaust. </TD></TR></TABLE>

ANymore about this Bottleneck,..is it a Factory bend/taper in the Piping?
Guess I could just look(1:01am ),..but any before & after pic's?

 

The "bottleneck" being discussed here is the one located at the flange where the OEM exhaust bolts to the cat. This flange has an extremely small opening (~1.75" I believe, but Dave at SMSP will have an exact figure for you) that abrubtly opens to the 2.25" OD piping. Cutting this flange and bottleneck out and replacing it with one that has a 2.5" opening and tapers smoothly to 2.25" is a good idea when running the stock exhaust with a 2.5" header/cat. Here are some pics I borrowed:

MugenFG360's pic:


A good shot by uncleben of the stock flange cut off and still attached to the cat: