climb_on

decided on my next upgrade on my car to be the exhaust end on my 2001 gsr

i was looking at the a jdm 4-1 header replica like the megan headers, great price and i think everyone here who ACTUALY has them seems to like them.

now here is where it gets complicated for me...

the collector is 2.5in so i need to get a 2.5in inlet and outlet cat. which is fine cause it would be good to upgrade to a high flow anyways.

now past the cat, what size exhaust will it fit? i was thinking about getting a ITR exhaust from a friend for cheap but will it fit.

i really confused as to how these different diamaters are suppose to bolt up. will the headers and cat work with my stock exhaust or the itr exhaust or another 2.5in or 60mm cat back.

Padawan

The flange that bolts to the cat is the same size regardless of whether the piping is 2.25", 60mm, or 2.5". Only the opening in the flange changes along with the piping size. Therefore, any of them will bolt to the 2.5" cat.

climb_on

ok so let me get this straight,

a header NEEDS to have a matching cat?

like a header with a 2.5in collector NEEDS a cat with a 2.5 inlet and outlet to bolt up

but....

on the exhaust end the flange that bolts up to the cat will fit a cat of any size.

so i could run the megan 4-1 headers that have a 2.5in collector like the jdm ones then i HAVE to get a 2.5in cat, but the exhaust can be a ITR or other aftermarket catback, and it will all bolt right up?

Padawan

Correct. You'd just need to make sure that the cat you bought was the correct length.

climb_on

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">Correct. You'd just need to make sure that the cat you bought was the correct length. </TD></TR></TABLE>

and how do i know what lenght to get i guess the better answer is what size is the 2001 gsr, cause that what size i would need right?

Padawan

If you order from a reputable source (I recommend SMSP), you just provide your setup and they'll ship you the proper length. You want the cat to be approximately 17" long.

climb_on

so 17" long is the leght of my stock cat.

so to run a 25in colector header i have to get a 2.5in diameter cat that is 17in long

is there any other companies that will carry these cats or can i just find a high flow replacement for my oem one?

Padawan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by climb_on &raquo;</TD></TR><TR><TD CLASS="quote">so 17" long is the leght of my stock cat.</TD></TR></TABLE>

The stock cat is actually slightly longer, because a "JDM-sized" header is slightly longer than a USDM one.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by climb_on &raquo;</TD></TR><TR><TD CLASS="quote">so to run a 25in colector header i have to get a 2.5in diameter cat that is 17in long</TD></TR></TABLE>

Correct.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by climb_on &raquo;</TD></TR><TR><TD CLASS="quote">is there any other companies that will carry these cats or can i just find a high flow replacement for my oem one?</TD></TR></TABLE>

SMSP is honestly the first company I'd recommend.

climb_on

i saw smps prices and the cat will cost more than my headers since im going with a megan exhaust.

thats whats kind of killing me

what about an adapter flange or is my stock cat too long to be used with the jdm style header.


Modified by climb_on at 2:15 PM 7/20/2007

climb_on

ok started shopping around and got confused all over again.

if i get a 2.5in cat can i only run a certain size exhaust?

can i just get an adapter flange to bolt up the header to my stock set up?

Padawan

Modifying the stock cat is a possibility, but you'll be bottlenecking the new header with the restrictive (and far smaller) stock cat. If that's what you want to do, you'd be better off simply sticking with a header that uses the stock 2.0" collector size.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by climb_on &raquo;</TD></TR><TR><TD CLASS="quote">if i get a 2.5in cat can i only run a certain size exhaust?</TD></TR></TABLE>

I thought we went over this. See my above posts.

climb_on

i found a compromise between moding my stock cat and paying big bucks for a custom cat....

TEST PIPE....way cheaper!

climb_on

padawan just wanna thanks for all the help and patience so to cap this post off this is what the plans are for


megan 4-1 jdm style header with a 2.5in collector
to a
2.5 inlet and outlet obx resonated test pipe or car sound high flow cat
to a
2.25in or 60mm(2.36in) cat back maybe going with the itr, or the ws2 something quiet that will provide a little back pressure.

any comments?


Modified by climb_on at 7:58 PM 7/20/2007

doood

iTrader: (1)

imo, why go with a decent flowing header like the jdm itr or a copy of it and then bottleneck it with a smaller exhaust? why not just stick with a "usdm" sized header?

climb_on

well first off the megan header is very affordable
and i need a bit of bottle neck for some back pressure

plust its cheaper then finding a usdm size header

doood

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by climb_on &raquo;</TD></TR><TR><TD CLASS="quote">
and i need a bit of bottle neck for some back pressure
</TD></TR></TABLE>

why? that's the last thing you want.

climb_on

well considering with an itr exhaust the smallest part of the system will be the exhaust tubing at 60mm or 2.36in its really not much of a bottle neck, but more a funnel from 2.5 to 2.36 lol

plus with stock internals i need some back pressure to properly run.