nickj

My FB won't smog. It's totally stock, starts easily, runs perfectly, but pollutes like hell. I'm thinking I can maybe change the cats. Anyone done this? Can I just replace one, or should I do them both? I only paid $1200 for the car, I'm hoping to avoid another $1200 for the exhaust.

BrianHeston

The pre-cats are actually just empty bulbs. At least from my experience. As far as I can tell they are just there to disrupt airflow a bit before it enters the cat, and possibly to give it a chance to expand and minimize the pressure going into the cat? Not really sure, these are all just speculation.

Bottom line, you should be able to replace only the main cat. Look here to find what you need: http://www.mazdatrix.com/e5.htm

Brian

purple82

For the longest time there were no choices for a catalytic converter replacement. You had to go to Mazda, period.

Luckily, you can now find a cat from any number of manufacturers at very reasonable prices.

If it was me, I'd probably upgrade to a header and replacement cat from Mazdatrix to get some power gain while I was spending the money. Total tally is about $650. This replaces the two cats with one.

You can also get replacement cats pretty cheap from Victoria British. I don't know how long they'd last... Depending on the year of your car, this will be $300 - $600.

Another choice would be to go to RX7.com and get a Bonez cat, it'll run about $250 which would also change from two cats to one. I also think that Randon Technology sells a replacement cat for about the same price. If not you can get a generic one and have it welded up to fit your exhaust.

purple82

Man, I hope there's something in there because it's $1700 from Mazda.

cdrad51

^ lol exactly. There is something in there. They break down different exhaust chemical components. However you can replace all three with the Bonez and will do the same for emissions control. Bonez would be my recommendation. And when you are done with the emissions testing, swap it with a cat replacement pipe from Mazdatrix. Exact same length. Bolt on, bolt off.

purple82

The first one is a reducer, taking the Os from the Ns, the second is an oxydizer, adding the Os to the Cs. Modern cats do both in one unit.

Junia

So if you upgrade to one of these newer cats you can eliminate the airpump all together?

purple82

Nope, the cat still needs fresh air from the pump. There isn't enough oxygen in the combusted air for the oxygenating process in a rotary.

Junia

I know that RE Amemiya has a cat thats a stock replacement and eliminates the airpump completely while still passing smog. Only thing is that I don't know how much of a difference there is between the U.S. and Japan smog limits.

nickj

Thanks, this is great info. Makes sense one cat should be able to do the whole job -- it does on most cars.

The $1700 Mazda converter scared me, too. I've gotten a buch of stuff from Mazdatrix, I'll go with their aftermarket unit.

Oni-kyan

I found a place online a while back, $135.00... It came with the right flanges and all. Just look around.

purple82

Whatever you get, make sure it's made for an Rx-7. If not, it won't last long at all. Of course for $135 you can stand to go through a few.

cdrad51

Mazdatrix's aftermarket cat won't bolt to the stock exhaust manifold, or it will, but you will have a gap to the mid connecting pipe. You have to either get RB's header with it or get the Bonez cat from Rotary Performance, rx7.com, which is cheaper anyways.

nickj

Thanks, cd. The Bonez cat it is.

Pele

iTrader: (28)

WOAH! I just realized where you're from. Peoples Republik of Kalifornia...

Lemmie know how it turns out. That'll be thr true test of any Cat.

wae

I was under the impression that in California, if you don't have the right number of cat-looking-things under the car, they'd fail you without even putting the sniffer on...

I don't really know for certain, but be sure that replacing 3 cats with 1 is a legal move...

Pele

iTrader: (28)

That too...

Here if they see something BLATANTLY wrong, like an exhaust dump, air injection into the exhaust (dilution), or a turbo on a car that CLEARLY didn't have it stock, they don't sniff it. But if it all looks somewhat decent, then it's all on the sniffer.

They also look for evaporative system (Charcoal canister and ****), thermostatic system for the carb (little flapper in the blue box), PCV system, and some other small stuff. But that's either necessary or easy to add back.

13BTOY

iTrader: (1)

Dont our cars fall under the grandfathered out category since its over 20yrs old? I was talking to a buddy of mine in Canada and his car is an 83 and no sniffer test for him. Lucky bastard! LOL! Anyways, I guess it would vary from state to state. Anyone here from NY?



Thanks, Ed

purple82

It's state dependent.

cdrad51

BTW, I have an extra one laying around. PM'ed you.

apexme

sc doesn't enforce emissions yay

riofrio

I'm thinking about doing the same thing (Bonez cat to replace all 3). Does anyone know if this will pass the visual part of the inspection in TN?

nickj

The Mazdatrix replacements ($420 and $329) are 50-state legal. I don't see that claim made for the Bonez cat. I can ask my local smog guy what he'd do about it.

riofrio

Sure, thanks... let me know what he says.

cdrad51

I asked the guys at rx7.com about the bonez cat before I got it - they made the same statement. 50 states legal. It's actually the most effective, high flow, high temp resistant cat I've come to know.