Pros and cons of deleting cats??

[ross22davis]

I was wondering what the pros and cons would be of deleting my cats and getting a custom midpipe? any thoughts?

[Dmyerzzz]

I second this. I been wanting to take off the cats and just run straight pipe back for awhile now. Just haven't had the balls to do it.

[Reuffeo]

Pro - better exhaust flow
Con - can't pass emissions (if you have that in your state)

[Blitanicle99]

Pros: More power

Cons: Emissions, Loud... also could be considered a Pro

[LittleRichard]

Pros: You will now have a track-only car as it won't be street legal any more
Cons: You will now have a track-only car as it won't be street legal any more

It will likely give you a little more power, but it will not be enough to notice. There really is no serious advantage to removing it unless it has been damaged. The biggest effect of removing it will be to pump more crap into the air.

I am by no means a tree huuger hippy, but the disadvantages of removing it are FAR greater than any advantage.

Just my $.02

[tlamm]

Since its "illegal" to get ride of it. Then do the easy thing and break all the inside out and make it into a empty can or put straight pipes in it to cover it up. It would be a "cat" but won't...lol

[kiddM3]

I don't have a cat and as a result its obviously louder, smells bad, and i can't pass emissions or inspection. It does increase power and gas mileage, but its not worth taking it off unless you have a turbo setup, track, or autox.
I just recently cut a section out of the straight pipe so i can swap the cat in and out :D.

[ross22davis]

I don't have a cat and as a result its obviously louder, smells bad, and i can't pass emissions or inspection. It does increase power and gas mileage, but its not worth taking it off unless you have a turbo setup, track, or autox.
I just recently cut a section out of the straight pipe so i can swap the cat in and out :D.

So will it smell bad on start up or all the time? and how bad does it stink? I dont want to be driving down the road and have people dying behind me from the smell... but I do want my car to sound more aggressive and i already have an aftermarket muffler...


Pro - better exhaust flow
Con - can't pass emissions (if you have that in your state)

No emission tests here.... probably the one and only reason kansas is FTW haha :stickoutt


Pros: More power

Cons: Emissions, Loud... also could be considered a Pro

how much louder?

[LockDots]

If you already went as far as switching out the muffler, why not do highflow cats, headers, and CAI?

[ross22davis]

If you already went as far as switching out the muffler, why not do highflow cats, headers, and CAI?

Because im not sure where to get any of that... I eventually want to get headers but im not sure which brand or where to buy them from? I didnt even know they made Highflow cats... and I currently have a custom CAI

[kiddM3]

It smells bad all the time. When you have no cats/resonator nothing is getting filtered out which=pungent smell.
The aggressive muscle sound you will get with no cat..i love the way mine sounds but i had to sacrifice it in order to pass inspection :(. It still sounds good with the magnaflow muffler, but not as intimidating.

High flow cat:

http://cgi.ebay.com/ebaymotors/94109-Magnaflow-HIGH-FLOW-Catalytic-Converter-3%22_W0QQitemZ280349857351QQcmdZViewItem?rvr_id=&itemid=280349857351

[shreker]

dont they come with hi-flo stock already???

[cabezzzdb8]

I have a stock exhaust if I remove them, they are damaged btw, will it be louder, do not want louder its my dd, just dont want to spend money on new ones

[travis325i]

guys its really loud trust me i am runnin just shorty headers and a track pipe and turndowns before the diff until i get a new rear section and its not fun in a daily driver

[dRock13]

guys its really loud trust me i am runnin just shorty headers and a track pipe and turndowns before the diff until i get a new rear section and its not fun in a daily driver

thats because your exhaust doesnt exit the car. and you might smell it more because it will billow into the wheel wells and get tossed into the car some.

cant imagine it to be too loud. I run a 12.5:1 CR 464 BBO with solid cam and lifters, through a 3.5" exhaust with dynomax mufflers. It used to be my daily car before the M3 and I can't imagine it being worse. lol

oh, and it has no sound deadening

[travis325i]

no mine doesnt smell at all and its more of a drone you cant hear shit inside the car i know it would be way better if it came out the back i had to drive it back to michigan two times and it was a really rough 10 hours its more or less just the drone its horrible ha

[328istothebone]

1st off.. The smell, loudness, failed emissions are all true CONS. But the cat(s) have more to them than just for emissions purposes. Cats actually create backpressure in your system, and contrary to popular belief, some backpressure is good. If you rid of all your backpressure than your cylinder will not be able to fill to it's full potential (due to valve overlap mixture escapes) and you will be dumping alot of your mixture out through your exhaust valve. Therefore you're pre cat O2 sensor will read lean and try and compensate with more fuel. This is where people get "performance" from. When in reality you are just losing fuel economy and not really gaining a whole lot.

[FLYINV]

With the smell, just don't turn your car on inside your closed garage or let the kids get close enough to breathe in the exhaust gases. There's some pretty nasty stuff in there.

Best idea is to get flanges made up for the cat section so you can swap it in and out.

[bronzebbs]

I get a waiver everytime I have to show up to the emissions station with my obd1 "sniffer test" car. Coilovers ftw.

[dRock13]

btw, OP, your car is sik.

[Reuffeo]

No emission tests here.... probably the one and only reason kansas is FTW haha :stickoutt



none where i am either :)

[RatFink328]

I was wondering what the pros and cons would be of deleting my cats and getting a custom midpipe? any thoughts?


Youve already got DDM's exhaust system. Your car is loud enough!

Ive seen multiple dyno tests on multiple engine types (4 cyl, v6, inline 6, v8) and the power gains are minimal. Somewhere between 1-10 horsepower.

The major cons are that the car will smell (in a garage, it will make your eyes water).

The car will also pollute as much as 20 cars that still have cats on them.

Seriously, do the responsible thing and keep the cats. Theres a lot of other places to find power in an m52.




I LOLed at the photoshopped rims and drop on your car, BTW.

[LockDots]

1st off.. The smell, loudness, failed emissions are all true CONS. But the cat(s) have more to them than just for emissions purposes. Cats actually create backpressure in your system, and contrary to popular belief, some backpressure is good. If you rid of all your backpressure than your cylinder will not be able to fill to it's full potential (due to valve overlap mixture escapes) and you will be dumping alot of your mixture out through your exhaust valve. Therefore you're pre cat O2 sensor will read lean and try and compensate with more fuel. This is where people get "performance" from. When in reality you are just losing fuel economy and not really gaining a whole lot.


http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

+1/-1 You be the judge :D

[Dmyerzzz]

In Pa (some parts) they just do a visual test, no sniffer. So the best thing to do is hollow out the car and run a pipe inside. They are not aloud to bang on the cat to make sure its not hollowed out, if they do, they are violating the inspection rules. This guy in my auto class has a evo with no cats and a 3.5 exhaust and it doesn't smell, and the sounds not loud at all.

[RatFink328]

In Pa (some parts) they just do a visual test, no sniffer. So the best thing to do is hollow out the car and run a pipe inside. They are not aloud to bang on the cat to make sure its not hollowed out, if they do, they are violating the inspection rules. This guy in my auto class has a evo with no cats and a 3.5 exhaust and it doesn't smell, and the sounds not loud at all.

Its got a turbo though, that quiets the exhaust down a LOT.

[travis325i]

I have some pics up on my facebook of my car with just headers and the track pipe I will have to see If my buddy can make a YouTube video out of them or if not just add me on facebook it's pretty loud but sounds like a racecar haha

[kiddM3]

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

+1/-1 you be the judge :d

yay +1

This is what mine sounded like with no cat. (I used this video to diagnose my blue smoke problem, has been fixed so ignore title)

http://www.youtube.com/watch?v=dzCpvJJfq4A

[LockDots]

I personally trust UUC. They don't make cheapo stuff. I've got their SSK+DSSR and next is their Exaust. Still tossed up between both their models. Most likely going to go with System-U though, with Magnaflow cats, and Bavauto headers. :D mmmmm

[travis325i]

Its got a turbo though, that quiets the exhaust down a LOT.

Very true I had a 94 Plymouth laser aka dsm awd turbo with a 3 inch from the turbo back and just a magnaflow muffler and it wasn't that loud at all

[325istitan10]

I just have a borla muffler with no cats or anything. It doesn't smell and it's not loud until you hit around 3800 rpms. I can barely hear it driving on the highway. I would have never done it myself because Hondas without them usually sound horrible, but the bimmer is completely different it seems. I bought it the way it is and I like it.

[RatFink328]

I just have a borla muffler with no cats or anything. It doesn't smell and it's not loud until you hit around 3800 rpms. I can barely hear it driving on the highway. I would have never done it myself because Hondas without them usually sound horrible, but the bimmer is completely different it seems. I bought it the way it is and I like it.


Regardless, I just dont think that its very responsible to run catless. Im not saying that everyone should sell their e36 for a Prius or something like that, im just saying that for a marginal increase in power, and a little more sound, its not worth the tradeoff of spewing so much crap into the air.

Run a high flo cat if you "must have" that 3 extra horsepower, but please, for everyones sake, run some sort of a catalytic converter.

[whiteknight]

I heard that if you ran one of todays cars and an old muscle car that the differance in pollution is marginal. Besides, at least we all arent drivin muscle cars that get 8 MPG. You can "pollute" the air by using hairspray....at least with straight pipes we can have fun doin it. Look at all the cars that run badly or burn oil into the air. Our cars are runnin much better than those cars even without cats. My car still has cats, Im sure they are blown, and Im goin to go to straight pipes soon.

[328istothebone]

I heard that if you ran one of todays cars and an old muscle car that the differance in pollution is marginal.


Whaaat! :nono
That is a VERY misinformed statement. There have been so many emission control devices put on cars since the muscle car days. Please tell me you were joking with that one?

[fast84gti]

cars now are 80 to 90% cleaner.
EFI makes them even more efficient.
Timing and fuel map control really helps pollution.
Air pump also helps.
If you delete all smog stuff, car runs better, and more reliable over the long hall (Less parts to go bad, fewer air lines to leak). But pollutes like a MF.
I like the sound of a high flow cat. Especially here in CA. But if I was in a state with no smog laws (I am from MN).... I would gut EVERYTHING related to smog. Including charcoal canister and vacuum lines.
Having a cat will not hurt the power much at all. Leave it.
If you take it out, make sure to add an extra resonator.

[ross22davis]

I LOLed at the photoshopped rims and drop on your car, BTW.

:rolleyes i didnt even make the sig... I dont have cash now but eventually my car will look like that... even though its almost completely like that