DSMTalk Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum banner

cat questions

953 Views 15 Replies 9 Participants Last post by  Mafixstealth
i have a non turbo eclipse with the 420a motor and i have an exhaust leak it looks like it is coming from where the cat and the downpipe meet but i am pretty sure that i need a new cat anyway so i wanna replace it.

i know for a fact that my car needs the back pressure from the cat i was told this by the dealership the dealership wants 400 dollars for a cat i dont wanna pay that much for a cat so i need to know what after market cat i can buy for my car that will create sufficent back pressure and not cost me any more then a couple hundred dollars

please anyone who has replaced their cat with after market ones or has knowledge on the subject, i need answers

thank you
1 - 16 of 16 Posts
I do not think that the cat is the make or break point for the backpressure level in your exhaust. Keep piping diameter at the correct size for your app and go with a high flow cat in that same size. Probably 2.25" or no larger than 2.5".
Definately do not pay over 150 for a cat. 400 is f'n insane.
dealerships are rip off's they wanted $1500 from me for a used ECU,the dealerships are only good if you have a warranty and even then sometimes they like to say " its a wear and tear item so it cant be replaced", i hate dealerships, i took my 2000 m3 to a rasmussen dealership and they changed all my factory coding because i bought mine in germany and after that it didnt act right, kept stalling and circuits were going dead so i had to sell it and i ended up with my non turbo crap that i love dearly.
Ebay yields a lot of magnaflow high flow cats, good quality, real stuff. I got my smaller high flow 3" cat for around $60. You just need to find a shop that is willing to cut/weld it all in, I know a lot are lazy, don't make enough money, so they won't do it unless they use their own material and can charge extra $$.
so what you uys are saying is that i can spend like 80 bucks buy a magna flow spend like another 30 to have a shop cut and weld it and that should qork just fine with no knock problems and sufficent back pressure?
Yes, Yes and Yes... be sure that you stay consistent with the sizing as greenstreak said.
Just pick up the cat off of ebay and swing it by the shop and have Jim cut and weld it in for you. That is what he does all day long so it won't be like trying to convince a Meineke to do it for you on the DL.

ok sounds good then one more question though

what do i do about o2 sensors if i get an aftermarket cat?
You don't do anything. The O2 sensor doesn't screw into the cat....it screws in post cat into the exhaust.
ok so what brand cat do you reccomend my piping is 2.25

what is the cost for cutting and welding the cat in?
dabigbbadwoof said:
ok so what brand cat do you reccomend my piping is 2.25

what is the cost for cutting and welding the cat in?
Doesn't really matter...hell, just go to an exhaust shop and they'll have all the cats. you could ever want in every size you can imagine. Cost for cutting and welding in a new one would probably cost you around $30.
ok well thanks to every one who answered the info was appericated
I don't know where they got the idea that you need the back pressure from a cat. I'm running 3" with abselutely no cat and I have no issues at all. Runs so much nicer than with the stock exhaust too.
he's non turbo thats why.It's for scavenging purposes.I took my cat off on my 2gnt and i lost low end tourque.So i would keep it.I wouldn't put any piping over 2.25 for a street NA dsm.Good luck with it.
The cat adds backpressure, but not enough to really matter. The main source of backpressure comes from the bends in the pipe. The more bends, the more back pressure, the less bends less back pressure.

I'd almost imagine that 3" on a NA car would kill the poor 4 cyl motor of almost every last little bit of torque that it makes in the low end. But then again, I'm running 3" exhaust on my 82 Ford Pick-up with a 300, and it runs like a bat outta hell(for a 300 inline six).
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.