header-cat-exhaust sizing

[00dc2]

I am thinking about getting a new set of headers for my dc2r. The stock headers are not JDM length.

so when replacing the headers i need to replace the cat and the exhaust due to the lengths. i get that.

now the question i have is about pipe fatness.

i have read that its good to make sure the piping doesnt get narrower as you go from header to cat to exh. So i hear that the toda header like the mbit maximworks header i want to get has a 2.5" collector. what does that actually mean? 2.5" = 6.3cm. is that the internal diameter? external diameter? something else?

so this needs to connect to a cat. are the performance metal cats that toda au use 2.5" is size? what about JDM DC2R cats, are they 2.5" fat?

then comes the exhaust. i see that the thicker exhausts for dc2 are 60.5mm
http://www.team-integra.net/sections...?ArticleID=451

with the extreme ones being 63.5 and up.

So my question: is a set of headers with a 2.5" collector with a performance metal cat (~$550 from toda going by last group buy) and a RM01A (apparently flows well and not too loud) going to be a good combination interms of the sizing matching?

and what other flanges and gaskets do you need and why?

[ryuhou]

mm amusing how u get anal about all the mm/inch stuff just like i did
2.5 inch isnt an accurate measurement its just wat evry1 seems to say...
if u get a bolt on cat ie jdm or jdm aftermarket itll fit str8 onto header with the donut ring gasket which basicali takes care of fitment issues
or u can get any cat and a suitable test pipe (same brand as header?) - cut off the flanges and weld them on - ur exhuast shop should b able to sort it out for u easily
im allergic to welding so i got a jdm aftermarket cat - but thats just me
most jdm cats are 60/60.5mm and will bolt str8 onto any of the above options. gaskets will come with ur parts as u buy them.
open to mass corrections as i got 1 hr sleep....
yawn

[tinkerbell]

So my question: is a set of headers with a 2.5" collector with a performance metal cat and a RM01A going to be a good combination interms of the sizing matching?

yes it is.

[00dc2]

mm amusing how u get anal about all the mm/inch stuff just like i did
2.5 inch isnt an accurate measurement its just wat evry1 seems to say...
if u get a bolt on cat ie jdm or jdm aftermarket itll fit str8 onto header with the donut ring gasket which basicali takes care of fitment issues
or u can get any cat and a suitable test pipe (same brand as header?) - cut off the flanges and weld them on - ur exhuast shop should b able to sort it out for u easily
im allergic to welding so i got a jdm aftermarket cat - but thats just me
most jdm cats are 60/60.5mm and will bolt str8 onto any of the above options. gaskets will come with ur parts as u buy them.
open to mass corrections as i got 1 hr sleep....
yawn

hey, what aftermarket jdm cat did you get, where from and what was the damage?

i am anal about this cos if your going to spend 3k on some steel piping then it better be damn good piping!

[ryuhou]

theres alot of brands
i got a metalit cat from knightsports
used brown but not damaged
cost me like 450 to get in
=\

but yeah it did the job
alt u can get in just 96 spec jdm itr cats that are bolt on for less
but they wont flow as well
theres alot u can choose from