What's the View Here on Catless Downpipes/Cat Deletes?

[SchnellFowVay]

I am starting to see a growing majority of environmentally conscious Car Loungers making comments re: DPs, etc., that remove the catalytic converter.

While not admitting to tampering with the emissions control equipment on my own turbocharged car, I have heard that there are tremendous power and driveability benefits to going catless.

Everyone post up your thoughts.

[eunos94]

[FACTORYBOOST]

In Indiana, no inspections as of yet, so why not
One less thing to go bad on the car, and since it's a VW I need all the help I can get

[seroki]

Read this, then post again

http://auto.howstuffworks.com/catalytic-converter.htm

[71camaro]

I'm for it in a true high performance situation. If you're running a stock turbo or one that's a mild upgrade, on a daily, then I see no point.

[Spiller337]

I've deleted the cats on my last two cars. Installed a straight pipe with an O2 sensor spacer, and sold the cats for scrap. No problems with inspections or check engine lights.

[eunos94]

In Indiana, no inspections as of yet, so why not
One less thing to go bad on the car, and since it's a VW I need all the help I can get

Really? Why not? Well because there is almost no measurable gain in NOT running a high performance cat versus a straight pipe. So you're polluting just to pollute. That kinda makes you a douche.

[Rav_VW]

Personally I would be embarrassed if my car smelled like that all the time. I'll stick with proper high-flow catted downpipes.

[TurboMinivan]

Personally, I am very much against intentional pollution. I have never and would never make any street-driven car cat-less (assuming it had one from the manufacturer). When I was racing my firmer turbo minivan, I did upgrade to a 3" cat (along with the rest of the exhaust system) in the interest of minimizing back pressure, but I kept the car running clean (as evidenced by passing the local annual smog test).

Whenever someone brags about removing or gutting their cat, I see them as a clueless individual who doesn't understand how to properly make power.

[Cousin Eddie]

This is what's wrong with the world:

From the movie "21 Jump Street"

Eric Molson: Hey, is that your car?
Jenko: Yeah.
Eric Molson: What's that thing get, ten miles to the gallon?
Jenko: No, try like, seven. What about you?
Zack: Biodiesel.
Schmidt: Smells like egg rolls.
Eric Molson: Yeah, it does. Runs on left over fry oil from Hutong Palace, but we try ride bikes when we can. Global crisis and what-not.
Jenko: Whatever, man. I don't care about anything.
Eric Molson: Oh, you don't care about the environment? That's kind of ****ed up, man.

[Chris_V]

Really, with the advent of reasonably priced, high performance, high flow cats, there's no reason not to run them, especially when they really don't cost that much. I mean, the high flow magnaflow cats I put on the BMW only cost me $63 each.

Yeah, I remember the days when you could only get factory cats for a grand or more each and they choked the car up something fierce, but that's simply not the case anymore. You can be clean and cheap and have your performance, too. I have to agree with eunos on this one.

[6cylVWguy]

I don't really see the point in doing, personally. For today's engines/powertrain, the componants that give the car some performance and the parts for emissions work very well together, in constrast to cars sold when emissions equipment was fairly new.

I suppose you could gain a couple of hp, but to me, it's a very redneck way of doing things. Who cares about a handful of hp unless you're actually racing your car professionally. But for everyone else, it just doesn't make sense--at least in most instances I can think of. The cat converter just doesn't seem to be nearly the hinderance that it once was. I'd rather save the time and hassle for when I could put some real power adders on my car, like a turbo/SC or potentially even nitrous.

[AKADriver]

I have heard that there are tremendous power and driveability benefits to going catless.

From who, Bubba who punched out the cat in his '75 Camaro?

Generally speaking, there are three types of cat systems you'll find on most modern cars:
- A single three-way cat per bank of cylinders mounted a ways downstream of the header. This was the most common configuration between about 1980 and 2000.
- A single, three-way cat per bank of cylinders mounted tightly to the exhaust manifold. This is common on economy cars since about 2000.
- A warm-up catalyst or two mounted tightly to the manifold, and then a three-way cat mounted downstream. This is common on bigger engines or on cars that have separate CARB and EPA-spec models. Sometimes on Subarus this means the warm-up cat will be before the turbo (in the "up-pipe").

The downstream catalysts are almost never a restriction on a modern car. Removing these is almost always pointless, and when I see cars with those removed, running completely catless, my first thought is that the owner is a clueless Bubba who removed the cat because "ain't no damn gummint tell ME what to do."

The upstream or warm-up cats sometimes are restrictive, sometimes not. The biggest problem with these, in my view, is that they're subject to much greater exhaust heat and usually last just barely beyond the emissions warranty period. What's worse, in engines that use variable exhaust cam timing for EGR (Toyota 1ZZ-FE, Nissan QR25DE), when the cat dies little bits of ceramic get sucked into the engine and sandblast it. So I think there are sometimes good reasons to jettison these - provided there's a downstream three-way still in place.

[SIR ANDROID184]

Really, with the advent of reasonably priced, high performance, high flow cats, there's no reason not to run them, especially when they really don't cost that much. I mean, the high flow magnaflow cats I put on the BMW only cost me $63 each.

Yeah, I remember the days when you could only get factory cats for a grand or more each and they choked the car up something fierce, but that's simply not the case anymore. You can be clean and cheap and have your performance, too. I have to agree with eunos on this one.

I wish I could run these on my audi without a c.e.l, even with spacers im afraid of
getting a light and the stock cats are almost $900 each. I've heard from alot of
folks that even regular aftermarket cats on the audi's throw a code.

My rocco I bought came without a cat, after 3 months....I put a high flow one on, the smell
killed me and people in drive tru's would roll up their windows

[Chris_V]

I wish I could run these on my audi without a c.e.l, even with spacers im afraid of
getting a light and the stock cats are almost $900 each. I've heard from alot of
folks that even regular aftermarket cats on the audi's throw a code.

My rocco I bought came without a cat, after 3 months....I put a high flow one on, the smell
killed me and people in drive tru's would roll up their windows

I ran the spacers on my BMW. The stock cats were $1200 each on it...

[FACTORYBOOST]

Really? Why not? Well because there is almost no measurable gain in NOT running a high performance cat versus a straight pipe. So you're polluting just to pollute. That kinda makes you a douche.

Obviously obvious troll wasn't obvious
And my car still has the factory cat on it, and I will more than likely put a high flow on it if I upgrade the exhaust, but I'll probably just do a cat back since I'm not upgrading my turbo

[NashGTI]

Buy stuff from before there were catalytic convertors mandated

Profit?


I agree though, hearing someone suggest gutting a cat in this day and age just smacks of cluelessness.

[xtravbx]

In Indiana, no inspections as of yet, so why not
One less thing to go bad on the car, and since it's a VW I need all the help I can get

Yeah... catalytic convertors usually don't "go wrong."

Unless there's something wrong with your tuning, it should be fine.

I will always run a catalytic convertor. The power gains are not enough for me to have to deal with the terrible exhaust fumes, plus I don't want to be dumping that crap into the air I breathe.

[cockerpunk]

my 951 has a test pipe, and combined with a tune, seriously woke up the car, WAY more power (60+bhp) and better spool.

on modern cars its not nearly the problem it was on the 70s and 80s cars.

[jacobyb]

Going from Kooks catted mids (which are very expensive) to no cats pulled over 21whp on my GTO.

[Chmeeee]

To me, making a modification that makes single digit horsepower increases (at best) but massively increases the pollution you generate smacks of selfish idiocy.

[matty_peppers]

I would see huge gains going catless, but I currently rock one cat with a test pipe. Going to a full, high-flow catted 3" downpipe in the next couple weeks (I'm waiting to install it). It's just a matter of keeping it legal, as a young kid with a modded car I don't feel the need to have anything on my car that can give any person of authority a reason to give me trouble.

[x_GTI_x]

my buddies VR6T gained 24whp on the dyno with a test pipe compared to high-flow cats...

[Omnilith]

I like the muffling assistance a cat gives you as well. Often a single muffler is just too loud, but a muffer/cat combo is just right.

I run my Focus catless at the track, but with an OEM cat on the street... the difference in volume is huge, but the difference in performance is minimal.

[Shomegrown]

I don't think I'd ever go full catless on a street driven car. I have the pre-cats removed on my car, but the main catalysts are still in place and functional. No smell, and I still passed emissions inspections in the US and Germany with it so I don't feel too guilty.

[freedo84gti]

when i upgraded my 84 gti to a bigger exhaust (for 2" to 2 1/4") i didnt want to spend the money on a bigger cat, and since in pa at the moment any car pre 86 is visual emissions only, all i have to do is have the shell of the cat around the pipes for it to pass. just nneed to know its there, doesnt have to be functioning

[vasillalov]

The biggest benefits are for FI cars, particularly turbo cars. Lack of catalytic converters improves spooling time, response time and also reduces EGTs which helps A LOT.

On BMW N54 engine the catless downpipes will give you easy 40-60 whp and 40-50 wtq with proper tuning.

BTW, I just passed Illinois emissions testing last week.

[x_GTI_x]

The biggest benefits are for FI cars, particularly turbo cars. Lack of catalytic converters improves spooling time, response time and also reduces EGTs which helps A LOT.

On BMW N54 engine the catless downpipes will give you easy 40-60 whp and 40-50 wtq with proper tuning.

BTW, I just passed Illinois emissions testing last week.

on cars without a keychain turbo, the gains really can be pretty massive.

yes even on modern cars.

[vasillalov]

As a second note: I wonder how different would be the emissions of modern day direct injection motors compared to port injected motors and even carbed motors if the catalytic converters are not present?... I'd venture a guess that the DI motors will produce marginally less emissions than other motors simply because the fuel gets better atomization and more efficient burn is achieved.

[vasillalov]

on cars without a keychain turbo, the gains really can be pretty massive.

yes even on modern cars.

Haha yeah, the N54 does have pretty small turbos indeed. And this is the reason why so much power is made when uncorked.

[AggvGtivr6]

Get some nice downpipes, not those ssac ones, or atleast wait til their 3" comes out. JB weld a cat cover over the test pipes, and get the rear 02's coded out. Perfect.

Typical righteous Car Lounge response

[SchnellFowVay]

The biggest benefits are for FI cars, particularly turbo cars. Lack of catalytic converters improves spooling time, response time and also reduces EGTs which helps A LOT.

On BMW N54 engine the catless downpipes will give you easy 40-60 whp and 40-50 wtq with proper tuning.

BTW, I just passed Illinois emissions testing last week.

I have "heard" from a "friend" with an N55 engine with a catless DP, that hte gains are pretty huge and spool-up times are massively decreased.

But that same friend doesn't really like the smell, and feels a bit bad about the environment.

[greatfox]

I ran catless on my GTI (when I had it) and currently on my S2000. But since I don't (or didn't in the case of my GTI) drive more than 2,000 miles per year with them, I don't feel guilty. My DD has a cat and it will stay that way.

Edit: The reason why I do it on my S2000 is twofold. 1) It reduces the drone of my single 70mm exhaust (and makes the tone sound a lot better) 2) I gained around 10 hp (which is huge on an S2000)

The way I see it is if a sport bike doesn't need a cat, then my S2000 doesn't either.

[MCTB]

Get some nice downpipes, not those ssac ones, or atleast wait til their 3" comes out. JB weld a cat cover over the test pipes, and get the rear 02's coded out. Perfect.

Typical righteous Car Lounge response

Dont do it. Its not worth it, power wise.

[Cousin Eddie]

Screw the environment. Do it for the fire!