I am about to order Greddy headers and Greddy Evo II exhaust with AEM short ram intake. I also have a faulty catalytic converter so im going to order a new one. do i need to go with a high flow cat since i am opening up the airflow or just a new stock Honda cat? Everything is bolt on except the high flow cat unless anyone knows where i can find a bolt on high flow. I really would rather not do any welding if i can help it. Suggestions?

Also, it was mentioned to me that since you free up all that airflow with the I/H/E, that i should get bigger fuel injectors? Thanks for the help as always guys.

 

Let's take your second question first (I just want to be difficult).
Larger volume injectors are overkill on anything other than Blown (turbo / supercharged) applications. The stock injectors don't operate anywhere near their rated capacity. Even if you were to port/polish the head and install a larger throttle body, you still would'nt need them.
In addition the oem Honda Catalytic Converter can handle aprox 20% more flow thru without problems; but seeing that you're going the Header/Cat-Back route already, a TRUE High-Flow cat certainly wouldn't hurt.
I say "TRUE" b'cuz there's a bunch of cheap cra...p on EBay mascarading as HFC's while being no more that polished "test pipes'. Mount one of these, and the noise will drive you from the car (dispite Mr Fosgate"s best efforts).
if you get one, make sure it's dot approved and you can see a honeycomb element inside the case.
You didn't mention what year, so just remember to check if you need the O2 sensor provision

P

I just noticed your signature, you'll need the O2 mounting bung to stay legal

 

I went with SMSP. He makes different hi-flow cats.

Great guy

 

A true bolt-on will be Random Tech, google them, I got a direct replacement high flow version for my friend's 98 Civic and it works great, BUT, it cost alot more than you'd might like but it's a true bolt-on. Now if you don't mind having a muffler shop doing some welding, I've heard great things about catco which I think is essentially a magnaflow cat and you can get that from Kteller. Good luck.

 

magnaflow/catco high-flow cats get a from me.

just be aware that your greddy exhaust is going to get quite loud with a high-flow cat.

 

your high flow cat isnt gonna free up really much of anything...bolt ons can only do so much, and the greddy collector is smaller in diameter so it can match to your cat anyways

 

Thanks for the great suggestions guys. I know the I/H/E setup will make the car louder but i dont want to make it obnoxiously loud. i want a nice clean throaty tone. I guess i'll just go with the stock cat because it seems it will work just fine.

When i go to install all this stuff on the exhaust, will i need new o-ring gaskets between the header, cat, and rear exhaust? or will i be able to reuse what's on the car? I want to make sure i order everything i need so i can put it all on at one time. I guess i need to be sure to get a new exhaust manifold gasket right? Thanks again guys

 

use all new gaskets...the header should come with new donut/crush ring gaskets

 

Actually, some ppl will argue that the cat has NOTHING if little to do with noise control. BUT if you really think that getting a high flow cat will make more noise, just counter it with a resonator and you'll be fine.

 

Might anyone know if the Greddy Evo II has its own donut/crush gaskets that come with it? So i should get new ring gaskets for the whole setup? And does anyone know about these copper exhaust manifold gaskets? is that what i need to get?

 

trust me, my car ('99 Accord 4-cyl) proved that the cat makes a big difference noise-wise.

1. Cheapo cat-back exhaust + OEM cat (rattling and falling apart) = medium loudness, no drone.

2. Cheapo cat-back exhaust + high-flow cat = car vibrating/rattling at idle; deafening drone at ANY speed; utter hatred for driving.

3. New Magnaflow cat-back + high-flow cat = slightly quieter than #1.

4. Magnaflow cat-back +high-flow cat + 18" resonator = no notable difference from #3.

My cousin has the same Magnaflow cat-back on his '00 Accord, and his car is a hell of a lot quieter than mine.