Who Is Running Catless X Pipe

[art unique]

Originally Posted by Freiheit

No, thats not the job of the cats. They're strictly there to combat hydrocarbons, CO, and NOx, not play de-odorizer.

Our cars use three-way cats to get the NOx out, as do most cars made over the past thirty years. You have to have richer mixture than usual to make a three-way cat to its job to eliminate NOx. Take out the three way cat, you have a richer than normal mixture that smells like Amoco's colon. Adjusting the fuel mixture to lean it out at idle or off-idle will (or should) clean that up.

If you're removing a cat you should know the consequences. Leaning out your mixture JUST to eliminate smell is retarded.

[acarr6]

Originally Posted by Dlpfcb

Just curious how common this is to be fully catless. I searched the forums and found some information but not a lot of recent stuff. I'm considering a catless dual resonated x pipe and wondering how brutal the smell will truly be.

Mines pretty bad. Only noticeable in stopped traffic or drive thru windows LOL

[Redd]

I run full catless and I swear my exhaust fumes smell like 16-yrs old Lagavulin scotch whisky. 😂

[Freiheit]

Originally Posted by art unique

If you're removing a cat you should know the consequences. Leaning out your mixture JUST to eliminate smell is retarded.

Leaving it rich just because you don't understand VE tables or how cats work is a bit worse, pal. I had training in fuel injection about a decade ago. I don't know the latest EFI packages, but the principles haven't changed for 30 years. I'm trying to explain it to you but maybe I should do a better job.

When cars have 3-way cats, the cat requires a richer mix in order to mitigate NOx. Take out the cat and that fuel goes out the tailpipe, wasted. You can't hurt anything by eliminating that wasted fuel, especially at low/no load cells on the fuel table. Also, EFI systems on catted cars add fuel to cool the cat. Take out the cat, and guess what? More wasted fuel. If there's no EGT probe in the exhaust stream then the EFI is guessing at cat temp and automatically adding fuel. Does the S65 have an EGT probe? Guess what happens if you pull out the cats and don't lean out the idle table?

Now seriously, do you think you can't tune out the excess fuel in the idle cells on the S65 and stop the raw fuel smell, or at least a major dose of it? Do you think it isn't safe to do so? Many modern engines can run at stoichiometric or even leaner at idle and low load with no bad results. There's absolutely no reason to leave your car rich after a cat delete and say "that's the way it is, face the consequences".

[Freiheit]

Originally Posted by Redd

I run full catless and I swear my exhaust fumes smell like 16-yrs old Lagavulin scotch whisky. 😂

You know, desire smells like that to some people.

[opihi5]

Originally Posted by Ngilbe36

I am catless and I don't mind the smell. I actually kind of like it. A little eye burning helps you wake up in the morning!

This lol. Even the girlfriend likes the smell

When I swap stock cats on for smog the car feels unbearably slow and dull.

[art unique]

Originally Posted by Freiheit

Leaving it rich just because you don't understand VE tables or how cats work is a bit worse, pal. I had training in fuel injection about a decade ago. I don't know the latest EFI packages, but the principles haven't changed for 30 years. I'm trying to explain it to you but maybe I should do a better job.

When cars have 3-way cats, the cat requires a richer mix in order to mitigate NOx. Take out the cat and that fuel goes out the tailpipe, wasted. You can't hurt anything by eliminating that wasted fuel, especially at low/no load cells on the fuel table. Also, EFI systems on catted cars add fuel to cool the cat. Take out the cat, and guess what? More wasted fuel. If there's no EGT probe in the exhaust stream then the EFI is guessing at cat temp and automatically adding fuel. Does the S65 have an EGT probe? Guess what happens if you pull out the cats and don't lean out the idle table?

Now seriously, do you think you can't tune out the excess fuel in the idle cells on the S65 and stop the raw fuel smell, or at least a major dose of it? Do you think it isn't safe to do so? Many modern engines can run at stoichiometric or even leaner at idle and low load with no bad results. There's absolutely no reason to leave your car rich after a cat delete and say "that's the way it is, face the consequences".

I completely understand but that wasnt my point buddy. Tuning after a cat delete is a must, but if you're tuning for the smell. That makes absolutely no sense. Nobody is arguing about the benefits of a tune to a catless system. We're talking about the pussies crying about exhaust fumes at a red light.

[M3 Number 86]

the question is....who ISN'T?

[Freiheit]

Originally Posted by art unique

I completely understand but that wasnt my point buddy. Tuning after a cat delete is a must, but if you're tuning for the smell. That makes absolutely no sense. Nobody is arguing about the benefits of a tune to a catless system. We're talking about the pussies crying about exhaust fumes at a red light.

I hear you, but who hear is talking about getting a car tuned JUST for the smell? You'll already be in there tuning to max the car out after getting the cats pulled in the first place, so why wouldn't you tune to pull the extra fuel out? Its not like you'd be making a special trip to do it, "Oh damn the car smells I guess I'll have to do something about it" when its more "Hey while you're tuning out the cats, please adjust the idle and off-idle mix to lean as much of that out as possible". I think the main reason no one has it done is that no one wants to dyno-tune their car, and the canned tuners don't want the liability of leaning out the idle on a car that isn't in front of them.

I'm just trying to get the point across to you, that it doesn't have to be like that. The smell can be gone.
I mean, unless its some kind of test of manliness in your culture to have unburnt fuel odor. The Ramapan tribes used to cut off their own pinky fingers after being hung, for a day or two, suspended from hooks embedded under their chest muscles. I guess when you compare catless exhaust smell to something like that, the smell is a comparative bargain.

[JasonC.E46]

I've been running catless X-pipes for 4 years (with the Epic tune). While I mostly drive with the windows up, when driving with them down I really don't notice much than a passing whiff.

If you're working in your garage (door open, of course) and have it idling, then you can smell the difference.

What I'm really surprised by is that no one has mentioned the sound difference, which is beautiful. At idle and low RPM (< 4k RPM) it is tame/normal. BUT, when you get on it and get in the upper RPM band, it makes a wonderful roar; far better than stock. As such, in town you can moderate your sound by your driving/shifting style (6MT FOREVER!!!) and then let her roar when you want to.

+1 to previous poster regarding making sure you can pass any emissions in your area, if applicable.