_Julian_guzman

What’s up guys, I just recently took out my cat and installed an AP midpipe for the first time. Everything’s going good. The Only thing I was wondering is if it’s possible to minimize the exhaust smell. I understand that taking off the cat and putting in a midpipe is going to increase the smell of exhaust fumes. The only time I can smell it is if I’m at a red light and the windows are down. If windows are up even at idle the smell is non existent to me. I was thinking maybe the smell would lessen if I got a carbon exhaust gasket to create a tighter seal but I wanted to first hear some insight from you guys that also DD with a midpipe, thanks !

dannobre

iTrader: (3)

No CAT.... smells...

CAT... no smells

No real way around it. 🙄

TeamRX8

iTrader: (25)

well at least you won’t be the only mentally deficient person on here, you’ll have plenty of company with the other catless street car maroons.

CaymanRotary

Some places it's totally legal and the car may be louder and a bit smelly but at least sounds good. Replacement cats aren't so easy to come by (and very expensive if you do) and they just clog up anyways. So many benefits to run catless I just put up with the noise and smell. In fact, about to do the same to my truck today as the cat on that is now clogged as well.

TeamRX8

iTrader: (25)

well that didn’t take long to prove ...

UnknownJinX

Well, I guess it is between picking your own health and your car"s health(sort of). Remember that exhaust fume is toxic and actually addictive.

But yeah, without a cat there isn't a way around it. You need to weld a cat inline in the mid-pipe if you(and other people who are unlucky enough to be behind you) don't want to deal with the smell.

Unseen7

Man this forum makes me laugh sometimes. The only RX7 people who would be deemed to be "mentally deficient, street car maroons" over on RX7club would be those WITH catted midpipes.

My FC never had cats as long as I owned it and I've seen or worked on dozens of other 7s and maybe 2 still had cats. And the smell is honestly not much different, unless its a carbed FB 12A (which reeks either way). Furthermore I've spoken with tech at a Mazda dealer who confirmed that they're replaced several rennys because of failed/blocked cats, so I think from purely a longevity standpoint, going catless makes a lot of sense.

TeamRX8

iTrader: (25)

that’s because back in the day there weren’t proper cats available. Now with a company like HJS and their metallic cats rated for 1080*C that’s no longer the case.

obd2 changes things a bit too. as long as the sensors are happy it passes. the HJS cat is well proven on here by myself and others. I even had the 100cpi cat rated for 400hp and it never had any issue passing.

a $100 cat is never going to cut it though. given the things people waste money on daily there really is no excuse, but maroons gotta maroon ...

.

UnknownJinX

We all know that RX-8 ignition coils are made with potatoes, which in turn causes unburnt fuel to clog the cat. I'd be curious to see the life of a cat on an RX-8 with good ignition. As long as you don't go tracking with the stock cat, I'd think they are probably fine for street application for a healthy engine.

Again, your health or your engine health(sort of). You make your choice.

Unseen7

Yep I have no doubt that cat technology has come a long way since the 80s/90s to the point where it may no longer significantly negatively affect performance. However the fact that rotaries burn oil will always be an issue for cats clogging up eventually.

Regardless, whether or not cats are now a liability wasn’t really my point, it was mostly the needless derision directed at a very reasonable modification.

CaymanRotary

Even with a healthy engine and a brand new ignition system you will still have at least some unburnt fuel and oil go into the Cat. It's just the design of the engine and how it works. I enjoy my catless RX-8 and its 100% legal here to use as we dont have emissions testing. Thus, I have no interest in spending a fortune on something that will just be ruined again in short order. As for health concern, just roll your windows up and use AC on recirculate. I never even notice any smell...

UnknownJinX

I think oil would be the main concern. Cats are designed to process some unburnt fuel, even on piston engines(turbocharged piston engines at WOT run very rich as well).

Having your windows up and putting on recirc works okay until it rains... Personally I leave my car's HVAC on fresh air unless the air is bad outside.

Anyway, OP's question is pretty much answered, and as long as I am not driving behind you, do whatever you want.

TeamRX8

iTrader: (25)

bet if they put a paper mill next to your house with no emission devices on it you’d be complaining loud about it.

Just keep pooping in your drinking well too. clean air is an inexhaustible resource, we’ll never run out; right?

CaymanRotary

I somehow feel my RX8 isnt exactly causing all the global warming on the planet. If you think a catless 8 is bad, you should see the plumes of diesel smoke coming out of the 100 dumptrucks that drive around here all day long. I just dont want to spend money on a cat that will eventually be trashed and require me to buy another one. I'm not dropping thousands of dollars a year just for that!

TeamRX8

iTrader: (25)

because individual behavior is of no consequence

go back to my first post above, trust me I’ve heard every lame, full denial excuse there is to offer. Go back to my first post above. that’s you and your posts only bare witness to it.

CaymanRotary

Going catless is smart in this vehicle. It's not like I rip out the cat out of all my cars. Only when they are clogged and could potentially ruin my engine. You CANT buy them second hand, you CANT just replace with a cheap aftermarket one so your only option is to spend a fortune... on a car that constantly ruins cats. The rotary engine is dirty business. Dont blame me, blame Mazda for producing a car with an engine that was never designed to be efficient or clean.

UnknownJinX

Well, I have said all that's there is to say...

I don't agree with it but at the same time, I can't show up at someone's door that's thousands of miles away from me to stop them.

I would think a cat in a healthy and street driven 8 would last a lot longer than that.

CaymanRotary

We all have our own opinions I suppose. For me, it works, the smell doesnt bother me and it's completely legal here. I do agree it's bad for the environment and yes, it's a bit loud but to be able to just drive and premix my gas while never having to worry about my exhaust ruining my engine, I'll have a far better ownership experience. My other RX8 you'll be happy to know still has its factory cat. On that car, I will look into a replacement cat TeamRX8 recommended for a replacement when it eventually does bite the dust. In that car I also do not premix, just gets what the OMP gives it.

delhi

I think if your RX8 is a DD, then I'd suggest a high quality cat or find a stock cat. Both for emissions and smell.
If it's a weekender/track car that sees occasional use, it would no worse from those old classic cars (pre-cat days) in terms of emissions that get driven on nice days.
What drives me nuts are those diesel pick-ups that belch black smoke. I once saw one of these gunning it up a hill in front bathing a Tesla model 3 in dark soothe. I thought, what irony....

10KRPM

I have a question on premix and cat. Not meaning to get into the cat or no cat aspect, here's the quick explanation.

I bought it with cat removed and BHR midpipe, but PO gave me the cat. To get it inspected I had to install the cat. I am premixing, since I've owned it the oil consumption is so low, if at all, that I've got to service the injectors to see what is going on. Right now I'm short on time, but wanted to drive it in the meantime until I get the time to work on it. Eventually, once oil injection is addressed, I plan to run with a cat (I think anyway, might change my mind).

So my question - will running a few tanks of gas with 8 oz. to 12 gallon premix kill the cat? Or does it take a longer sustained use with premix to kill it? I could just take another car for now but much prefer to drive the 8. Thanks for any thoughts on this.

CaymanRotary

To answer your question, just a few tanks of premixed gas will not have much effect on the cat. To be safe, run half what you normally run for premix when you have the midpipe.

10KRPM

I thought about running less mix, but worry that if I have a non-functioning oil injection I might be hastening the demise of the engine. I'd rather kill a cat than drop compression! But maybe 4 oz. is enough to give adequate lubrication for the short term, that's one of those details that is hard to know for sure.

CaymanRotary

Maybe go with 6 oz. If there really was an issue with the OMP it should be throwing a code. Dont underestimate the value of the stock cat. They aren't cheap either.

10KRPM

Yes, definitely don't want to ruin it for a weekend of fun. I believe it is in pretty good shape, though need to look further into that as well to be sure.

No code for OMP. I don't put a ton of miles on it, but just don't see the oil level dropping by a cup or pint as I would expect, seems to stay on full or just a tick below.

CaymanRotary

It takes a bit for it to drop. I daily drive mine and check it every second time I fill it up. Usually put half a quart in per month and I drive roughly 600-800 miles per month.