Whats up guys, I have an 01 GS with mismatched piping that makes the check engine light pop up, making a noise when I stop (missing bolts with springs on the cat i think) and robs power. It came with a non-brand highflow cat from mr. motorsports that's 2.5" that I want to replace with a more suitable and affordable cat. Since its non-vtec, bonestock, I figure 2.5" is way too big for my needs, maybe even 2.25". and cheap headers from option racing that I cant find the diameter/outlet size anywhere. So I'm not even sure if the headers are 2.5" also.

My question is, I want to know whats the integras factory exhaust piping diameter ? The stock cat from Honda is way too expensive, around 600-800, way out of my affordability range. I was looking at a Magnaflow carb compliant cat for $236 with good reviews, passes emissions, and has the 02 bung for OBD2 02 sensor. Has to be welded on but not a problem for me. It's 2" in diameter, and not sure if mismatching piping would cause any problems or rob power... ?? I want to have a setup that passes emissions, sounds decent, adds a little power, and is affordable.

Is 2.25" right for stock non-vtec motors??? or too big? If so, can anybody recommend a good affordable cat..

oh and do you normally need bolts with screws when installing a cat? 'cause I thought I saw on the OEM car blueprint, there's some bolts with screws. I heard the exhaust needs to move with the motor and I think that's what may be causing this knocking sound when I let off the gas or press gas or stop hard..not sure if its the cat and headers being compressed together or the headers hitting something..idk

Thanks

 

for adding power, and staying stock, keeping a good cat and everything bolt up i would go with a USDM ITR exhaust system. its stock a 2.25"

LS-GS-GSR are 2"
JDM ITR are 2.5"

 

just do 2.25... I wouldnt think your miss matched pipes would throw up a code... there are other problems there

 

any suggestions on what specific aftermarket exhaust thats 2.25? type r exhaust must be hard to find and pricey.

 

Mismatch piping is not the cause of your Cel

 

right now im running a dc header, usdm itr cat, and apexi n1 catback. its all 2.25.

i want to upgrade to 2.5" but i also want to turbo my integra, thats probably they only reason why i havent gone to 2.5" yet

 

i believe the factory piping size is around 1.8-1.9". do you have a stock engine? if so, then the proper size to get for an aftermarket exhaust is 2.25". it's suppose to be about 1 square inch of cross sectional area per 60hp to the flywheel. 2.25" handles up to 210HP @ the flywheel (about 180-185 whp).

as far as the bolts and screws, i believe there are 3-4 bolts on each side of the flange that hold up the catalytic converter.

 

A friend ran 3" on his na ls and it made a noticeable difference. Wasn't to big but most systems these days are 2.5"

 

depends on ur future mods but u cant lose with 2.5"