cats reduce smell?

[AA-ron]

I'm planning out my exhaust on my Roadster (picking it up in two weeks...wow!) and wondering if any of you have any real world experience with whether or not catalytic converters reduce exhaust odor enough to use that as the primary reason to install them. In other words, I don't needs cats, but I suspect they might reduce the exhaust odor a bit and am wondering if any in this group can offer up some advice on the subject.
The engine is a 302/sniper combo from Forte.
My wife has a very sensitive nose-- just trying to remove date night conflicts.
Thanks

[michael everson]

If the engine is running correctly you shouldnt get a lot of gas smell. That said, no I dont think cats will reduce any smell.
They do reduce exhaust noise though. Not worth it on my opinion though. Lots of down sides to that type of exhaust system.
Mike

[CaptB]

As part of their purpose they certainly reduce the smell. More experienced folks here can talk about specifics on a MK IV though but it's always a good question. While I may not mind any smell, the wifey might!

[Blitzboy54]

I ran mine first straight then with cats. The difference was astounding on my car. With straight pipes with both the garage doors open it would stink and burn my eyes, my wife complained about the smell even in the driveway. Now with them installed the car has nearly zero exhaust smell. I also like that it gives the exhaust a throaty less metallic sound. It is still plenty loud. You give up some HP but for me at least not enough to matter.

I documented it in my build thread.


Quick disclaimer. I had my engine tuned after the car was complete. It was running very rich and is not anymore so I have no idea what it would smell like now.

[facultyofmusic]

As others said, the engine tuning makes a big difference and I'm not sure how much the cat will help on a badly tuned engine. A datapoint from me: I have a Gen 3 coyote with factory ford ECU (which according to other build threads is supposed to burn rich from the factory given our roadster setup); no smell after the initial warm-up. I know I have a sensitive nose because I've met up with guys without cats and I can smell them from a house away.

EDIT: Since noise is being discussed I'll chime in on that too. Even with a coyote + cats the exhaust is LOUD. IMO the reduction in harshness of the tone due to cats is strictly a good thing.

[egchewy79]

regardless of the smell, I think the wind blown hair is what keeps my wife from agreeing to take the cobra on date nights.

[J R Jones]

Early in my life I burned the hell out of my leg on a 1967 427 Corvette Roadster exhaust and avoided that configuration since. However we raced a 1954 Corvette roadster in Lacarra Pan America with the Blue Flame six at 257hp. It had side exhaust with no cat or muffler. We ran from dawn to dusk for seven days and took no time for breakfast. Indeed given the exhaust noise and fumes that rolled into the cockpit, I had no desire for food at lunch. Fluids only. Despite that, every day at 2PM I was sick to my stomach, but did not puke. That would have been tough with the task at hand, helmet and fire suit. You often do not actually smell carbon monoxide, but it gets in your bloodstream through your lungs. BTW the Corvette clocked at 127MPH.

[Chopper]

Cats do hold a lot more heat. I have cats on my car now, and they still stink until they get warm enough to do their job. That said, I'm going the other way...got some headers in the garage waiting install. I just don't like the J pipe routing or how much heat cats hold. I am not required to do cats, originally did they do mellow out the sound a bit...now I've got a set of gas-n pipes on order to that end.

One caveat to all this is, I am running EFI so, probably keeps the mixture a bit more stable regardless of weather, etc.

[Windsor]

You can smell the difference whenever you get behind a (production) vehicle that had the cats cut out of it.

[facultyofmusic]

regardless of the smell, I think the wind blown hair is what keeps my wife from agreeing to take the cobra on date nights.

What!? But that's the BEST PART! :p

[Straversi]

The smell that bothers my wife is gas, not exhaust. My other classic car with a carburetor and rubber fuel lines smells like gas sitting in the garage. I used PTFE lined hoses on the Mk-IV and there is zero gas smell. One day, I will convert the Caddie to fuel injection and I’ll swap out all the old rubber hose and put a charcoal filter on the fuel tank vent.
-Steve

[nucjd19]

My wife can't stand the smell of the exhaust ( running no cats with Carb). So I kill the engine in the driveway and let it sit for a little while and then push it in the garage. It would be nice to reduce the smell some. That being said...... My daughters LOVE it!

[Larry J W]

I have had both cats and a standard muffler on the 818. The cats differently reduce the smell while driving. It does take a minute or two for the them to warm up. Because of the fumes in the cockpit I am going back to the cats.

Larry

[GoDadGo]

No, cats don't reduce the smell of anything.
They smell like poop & pee if you don't clean their litter box.

[rthomas98]

No, cats don't reduce the smell of anything.
They smell like poop & pee if you don't clean their litter box.

LOL, I almost responded with this same post.

[rich grsc]

No, cats don't reduce the smell of anything.
They smell like poop & pee if you don't clean their litter box.
We can certainly agree on that.;)

[Jeff Kleiner]

https://www.youtube.com/watch?v=ukiD7YyCK9g&feature=youtu.be

Cheers,
Jeff

[toadster]

if you have/get cats - be sure to have your engine tuned, an overly rich exhaust will basically melt your cats and have zero benefit

this happens quite often on miata's where the cat is placed so closely to the exhaust ports, ask me how I know ;)

[jts359]

Back in the day when they were building TR-7 Triumphs The union shut the plant down for Stinky cat pee on pallets , During the cars short life I think it was built in 3 different plants , I dont remember which one , Ed

[Dave 53]

I have had both cats and a standard muffler on the 818. The cats differently reduce the smell while driving. It does take a minute or two for the them to warm up. Because of the fumes in the cockpit I am going back to the cats.

Larry

I started with a cat on my 818. Then I switched it out for a muffler and had horrible exhaust smells. Then I added an extension to the pipe. Not very much, but it solved the problem.
Seems if the pipe isn't long enough, the fumes just get sucked back into the engine compartment.
171333171334

When I really want to lengthen it out (and point the noise to the left - Laguna pipe). 171335