Well from what I have heard too much unburned fuel can be a problem. The fuel burns in the cat when the air from the air pump hits it and it basically melts. This is just what I have heard though. I have never seen it firsthand.

As for the sulfur smell I heard that is normal with new cats. I got it as soon as I put my HF on and it is slowly going away.
dis1

 

Random Technology also has metallic substrate cats now..

http://www.martelbrothers.com/custom...cat=550&page=4

I'm going to try out one of these, or the one Jimlab posted soon..probably the latter since it has actually been tested.

 

yea thats correct

 

who makes th ebest quality metallic cat? random, rpm or knightsport? they are the only one si have heaqrd of. are they all bying their cat material fromt he same place? is there any feedback on the knightsport cat yet?

 

I run a midpipe and my car doesnt smell half as bad as you guys are making it out to be. Sure, it does smell but not like rotten eggs or cigarette smoke. The term I would use to explain it would be an exhausty smell.

 

Agreed. It may have a fuel smell to it, but it's not eye-watering, nor is it strong enough to make your clothes smell. These guys must be doing something wrong.

 

I have to disagree there. It does make your clothes smell and if you don't notice it, you are just too used to it.

 

Maybe you shouldn't spend so much time standing next to your exhaust pipe...

I've been around several FDs without cats and none of them stank. I can't imagine what you guys would do standing around a Top Fuel car in the pits at an NHRA event. Now that's eye-watering stink. Last time I checked, most FDs don't burn nitromethane, though.

 

I bought one from Gotham Racing and it allowed me pass Illinois emmissions with the stock ECU. Two years later, I think it is dead. I failed 3 times! I do believe the high EGT burned it up. I am thinking of a Bonez hi flow. They claim it is better designed for the rotary temperatures.

 

Without a cat the exhaust STINKS, it isn't some light "exhausty" smell it is something that will stick with you all day if you stand around it...

Jim your memory is fading, last time I checked your car hasn't run since 1998.

 

Yeah, and I couldn't possibly have any friends with running FDs...

I reiterate my opinion that you may be overly sensitive.

 

I'm not the only one that says the exhaust stinks without the cat on a rotary. Review the posts, several people mention the stink without cats.

In reality, stink is relative, if you don't think it stinks then fine. I think it does. I think emissions testing a cat-less rotary verifies that they produce more emisssions (particularly hydrocarbons) than a piston motor. I think that when I went back into work after driving a cat-less rotary at lunch people mentioned that my clothes smelled like exhaust.

Who owns these FDs that you have been around recently.

 

Review my posts. I said they must be overly sensitive too.

To start with, Brian Goble (Scorpio), whose non-sequential '94 R2 I work on occasionally. Most of the local (and not-so-local) FD owners know me and have been by my place from time to time to pick up parts or bushings. Martini, RX7-2JOCK, AndyGoerdel... should I go on, or is that enough?

 

Have all your buddies post that the exhaust doesn't stink with a cat. Maybe now I understand why you think non-seq isn't laggy. I'm too sensitive and you have no sense.

A cat-less rotary pollutes at least couple orders of magnitude more than one with a cat. Now I don't expect everyone here to understand that but maybe you can.

 

Isn't this a subjective opinion we're talking about? I don't think it stinks. I disagree. What's your motive here Jeff? To change my opinion because it doesn't match yours?

My car was uncorked for most of the time it ran and never once did I think to myself "wow, the exhaust stinks so bad I can hardly stand it". I hated the soot on the rear bumper. I hated the sound of the exhaust. I hated the noise. But never once did I say "gee, I wish the exhaust didn't stink so bad". No one EVER commented on my car's exhaust stinking.

My friend Brian's car doesn't stink horribly either, that I've ever noticed. Maybe it has something to do with the programming of the ECU (we both have/had M2 ECUs). Maybe it's something else. I've stood around the back of his car while it was idling and except for a slight fuel smell, never thought that it stank, and my clothes didn't stink later on like they would with cigarette smoke. But once again, this is a subjective measurement. This is my opinion.

Sure Jeff, and maybe you can explain to me again how weight has a diminishing effect at high speed? By "sensitive", I really meant "overtly homosexual", but I was trying to be polite.

I understand that fully, and in fact, understand how much fuel the rotary dumps into the exhaust better than most self-described rotary fans on this forum. However, that doesn't mean anything more than what I've described several times now as a "fuel" smell. It doesn't stink like rotten eggs or stick to your clothing if you walk behind the car in my opinion, and for the last time, this is my opinion.

 

So now your name calling???

Yep the wieght thing seems to be a mistake on my part, turns out I was wrong.

What about you and your painter's Glasurit opinion? You sorta turned that into fact didn't you? Called rzo whatever pretentious and boorish then apparently apologized in private.

We all have our moments, why is that relevant to this thread?

Now what's up with the homosexual comment?

 

What do you call your quip about my having no sense? No sense of smell would have been humorous. No sense implies something else entirely.

Actually, it was my opinion. You only assumed that I consulted with a painter before stating it. I talked with my friend (a painter for nearly 20 years) about it afterward and he agreed that there was no justification for the hype and that if they priced it so ridiculously that they'd price themselves out of the market.

Because there was no justification for publicly humiliating him. I didn't apologize to him about my opinion. His dollar amounts were obviously inflated, and he was obviously trying to impress people with how special and expensive his paint was supposed to be.

You seem to be having a lot of them these days.

Perhaps "prissy" is the word I was looking for. Bordering on womanish.

 

Well, it all depends on what you get used to. If you work with cars all the time, there are smells you just get used to. Kind of like going into a public restroom when someone is sitting on the pot. You wish they would do a "courtesy flush" but they have been sitting their long enough they don't know how bad it stinks.

Way back when, I took my car to a mechanic when I first started having a "gas odor" problem. I had several people experience it, yet the mechanic couldn't smell it. He admitted that unless he sees gas pouring out from the engine, he wouldn't notice it being too used to exhaust and gas smells.

Jim, I think you are in the same boat. When I removed my airpump from my hi-flo cat, I about passed out. However, after a week or two I forgot all about it. There is a difference if you aren't used to the smells.

To anyone considering using a cat-less FD for daily driving duties:

If your job requires business attaire, I would recommend not driving to work in a cat-less FD (or any cat-less car) as you will reek of exhaust to the rest of the people in your meetings that aren't used to the exhaust smell. And that's not a good thing if you are trying to move up in the company.

 

Fair enough. But...

You're kidding, right? The interior of my car still smells new, and I've never smelled an FD that smelled like gas inside. Soot up the rear bumper is the worst side effect of a catless exhaust that I've ever seen.

I'm not calling you a liar, and I'm not saying it isn't possible. I'm just saying that I don't see how it's possible unless there's a leak in your exhaust system and a few holes in your floorpan.

 

My '93 VR6 Corrado didnt have a cat, and it was chipped, and the exhaust didnt smell any worse than a stock car with a cat. Sounded mean though (uncorked VR6 is easily in the top 5 for best sounding motors at redline)

 

Rotary engines dump a lot of unburned fuel into the exhaust and oil is injected into the combustion chamber. It's a little different.

 

I think that the smell may have somthing to do with the downpipe as well. I am under the impression that the stock downpipe is somewhat of a small cat and then it runs to the main cat. Are any of you guys that say the exhaust stinks, running a downpipe and midpipe?

I think I am on Jim's side on this one. My car hasn't run a cat in over two years and I have yet to be repulsed by it.

In response to the thread, I think that with the stock twins, a high flow cat is the way to go. Yes they will die after a while but I think that keeping boost spike to a minimum is a good thing.

 

Im aware of that, but Mahjik said any car, in parentheses. I was just giving an example of an "any car" that didnt stink without a cat

 

Fair enough. My Supra didn't stink either, and yes Jeff, I've been around quite a few of those without cats too.

 

For me, it was mainly sitting at lights (i.e. the car not moving). With the car moving, obviously, there was no problem. I would imagine the amount of wind would also play a little bit of a roll, but it really doen't take much to get that exhaust smell to sink into clothes. Anyone not used to it will smell it without you needed to sit in front of the tailpipe.

Try driving behind a cat-less Mustang on the highway then come back and post.