mcfly4001

hey, i think my main cat is clogged, i have already gutted my downpipe, and the only other mod i have is a BOV, would it hurt my car to gut the main cat? would i have to upgrade the computer? will this effect the o2 senor?

thanks

Mahjik

iTrader: (1)

The O2 won't care about it.

Since the stock piping isn't 3", you might be ok, however you'll need to keep an eye on your boost level. Anything over stock levels on the stock ECU could spell "rebuild" since gutting the cat will be less restriction even if not at 3" all the way through.

mcfly4001

thanks once again mahjik, um, i understand what ur saying, but has anyone did this, i would like a for sure, that i will not explode my engine?

i have alread gutted the down pipe remember, and have a BOV, thanks

GoodfellaFD3S

iTrader: (213)

I'd recommend getting a high flow cat. Gutting the main will lead to turbulence, among other things. You can find high flows new for under 300 bones if you look hard enough....

JONSKI

What will turbulence do?

GoodfellaFD3S

iTrader: (213)

Hinder exhaust velocity.

mcfly4001

why would a gutted cat, hinder exhaust velocity, bc, its not a constant diameter, throughout the gutted cat?

GoodfellaFD3S

iTrader: (213)

Yup A pathway that is straight and smooooooth is optimal.

mcfly4001

coudl i not go to the local muffler shop, and get them to make me a pipe, with a constant diameter, for about 30 bucks, and that be my midpipe?

DamonB

Yep (though you won't get stainless for $30).

mcfly4001

i can get the pipe for free, i just need the labor, thanks though

Mahjik

iTrader: (1)

Yes, you could. However, with the stock ECU, you need a cat welded in there somewhere or else you risk increasing the air flow too much. The other problem is what cat will they use... The generic cats probably won't last long with the exhaust temps that these turbo charged rotaries put out.

Check out Gotham Racing. I've heard they have a cat that is comparible to the Bonez Hi-Flo cat, but a little cheaper. IMO, that would be your best bet.

I do prefer the Bonez exhaust equipment, however they are very expensive: http://www.rx7.com/cgi-local/3catalog.cgi?cat=4&part=2

mcfly4001

so, u think that theres a good chance, that my engine will blow if i have gutted precat and main cat, on the stock ecu? i guess i just need to test my main cat and see if its clogged, could i just unhook it, and see how my car runs for just a few mins? it would have no type of exhaust for the time period, is this dangerours?

GoodfellaFD3S

iTrader: (213)

Yes, no, and yes .

mcfly4001

well how in the world do u know if ur cat is clogged and u dont really want to put several 100 dollars in it right now to do any upgrade, bc ur dog is sick!

haha

im so funny

but really?

paul

DamonB

From a previous post:

My main cat died a few weeks ago. The only symptom I had was that all of a sudden I went from 11-9-11 to 9-5-7; no matter what I couldn't get more than 7psi on the secondary. I was on the track at the time and in a span of about 10 minutes the boost kept falling until it stayed at 7psi max.

I pulled the cat and dumped handfulls of brick and wire mesh out of it. Installed another stock cat and the car was perfect again.

No smoke, coughing, sputtering or anything, just less boost.

Imagine a clogged cat like a clog in a drain. As long as there is not too much water coming through there are no problems, but once more tries to pass than the clog can let by, things back up. Since there is less exhaust volume in the primary turbo (less engine rpm) its boost is not affected as much as the secondary turbo (high engine rpm). My results support this as my primary was only 2 psi low with a clogged cat but my secondary was 4 psi low.

mcfly4001

i understand what yall r saying, and agree, but everyone tells me, about the third mod rule, and that is to upgrade the ecu, this would only be my second mod, the gutted downpipe and the gutted main cat, with exception to the BOV, which i was told that is really not a mod, so why would this blow my engine, i thought that the stock ecu could handle this?

thanks

Mahjik

iTrader: (1)

The three mod rule is really for "air flow mods". Mods which increase the air flow, thus making the car run leaner than stock. *IF* you can keep the boost at stock levels, it's not a problem.

However, the problem with opening up the exhaust is that it can make controlling boost a problem. There are some people here who even after porting the wastegate still can't control their boost with an open exhaust (no cats), but at least they have an aftermarket ECU.

If you experiece boost creep on the stock ECU, you could quickly be back to having your car as a garage ornament waiting for a rebuild or a reman.

mcfly4001

well crap, i wish there was a solid way to know it my main cat was clogged, without spending a lot of money on just buying a new one,

anyway, thanks

airborne

its a bitch but take the cat off and have a look inside. that'll tell ya sure enough. and its free.

mcfly4001

well i look inside, and its full of black sut, quite a bit, but most cats are, i just figured the clog, if there is one, might be down in there, where i cant see, im starting to think a stick of dynamite might fix my problem

thanks yall

jfirko

the "problem" you refer to exactly? You never stated a problem, only that you wanted to replace the cat. Maybe if you list your symptoms someone can point you in the right direction. As far as I know a clogged cat can make a car sluggish, limit boost, you could hear some rattling, you could blow exhaust gaskets, If it gets bad enough the car may stall, etc. I think if it were clogged then if you take it off and look in it you will see parts of the honeycomb breaking down. If you put a light at the one end I think you should be able to see the light through the honeycomb at the other end. I've never had my 3rd gen cat off and am by no means an expert.

DamonB

well I just posted some symptoms above

Take off your cat and look in there. Unfortunately guessing and wondering will never get you an answer.

kwikrx7

I had Meineke weld on one of their performance hi-flo cats onto a 3 inch midpipe 2 years ago and it's running fine. And that's running 14-15 psi with no air pump - still, even if I replace it once every few years, the cat was only $150 installed. This topic is somewhat like the "engine will blow if the stock injectors are maxed out" - nobody has really proved it - same with a cheap HF cat - nobody has ever proved they can't withstand the rotaries extra heat. But that's why people spend $500 for a HF cat - for that unproven "insurance" that it "can" withstand the extra heat by a rotary engine.

mcfly4001

hmmm, so do u think i could gut my main cat kwikrx7? and not blow my car up, has this been proven?

thanks