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      02-27-2012, 02:32 PM   #1
Keik E92 M3
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debating: Remove Primary cats or OEM exhaust mod?

I am debating between the two, i heard doing both will be to loud and drone. So i am curious from others who have done this. I am leaning more towards removing primary cats only. Smell bad?
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      02-27-2012, 02:54 PM   #2
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Remove the primary cats and leave the secondary cats in, going this route will reduce the smell greatly (I have compared both) with a good aftermarket catback you will not have that raspy sound that you will have with the OEM mod. you should invest in a Megan exhaust if you don't want to spend too much for an exhaust, great value for around $600. The sound is not too loud it's more bassy, the only issue I had was at start up until the car warms up it got pretty loud especially if you start up in a garage but I just had a tune and took off the heat cycle for the cats (no need for that if you go catless) I am very happy with the tone of the M now, over 4000rpm the car also gets quieter.
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      02-27-2012, 03:01 PM   #3
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removing second wont do SH** just take the primary ... please be advise that if you have a OEM axle back exhaust it will be LOUD... but it will be nice... POWER INCREASE.. WISE.. SCREW THE SMELL.. lmao
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      02-27-2012, 03:18 PM   #4
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I have been fully catless on my 335i b/c the power gains were substantial with a tune..and yes..it will smell bad..

On the m3 I only did OEM exhaust mod..to me the cost, warranty issues and smell caused by removing the primary cats is not worth the modest gains
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      02-27-2012, 03:26 PM   #5
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Just an FYI the OEM modded exhaust with a catless x pipe is the worst sounding exhaust ever. It sounds like a shitty 2-stroke dirt bike. Trust me, I had this setup for about 10min before I decided to put the car back on the lift and change it up.
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      02-27-2012, 03:26 PM   #6
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there is no smell from removing primary cats on this car

the sound is louder than stock when you are on it, but very similar at lower speeds.

the engine sound takes over at about 4500 rpm which i personally like
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      02-27-2012, 03:35 PM   #7
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So leave the OEM exhaust alone and just remove the Primary cats correct?

Thanks guys.
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      02-27-2012, 03:38 PM   #8
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Quote:
Originally Posted by KennyPowers View Post
there is no smell from removing primary cats on this car
No way.. dont believe that..any time you remove primary cats on "any" car you will have more smell..maybe leaving secondary cats in there would help..but only when they build enough heat in them..also OP needs to know he will get CEL by removing primary cats so he will need a tune to suppress it.
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      02-27-2012, 04:02 PM   #9
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Quote:
Originally Posted by tibra1 View Post
No way.. dont believe that..any time you remove primary cats on "any" car you will have more smell..maybe leaving secondary cats in there would help..but only when they build enough heat in them..also OP needs to know he will get CEL by removing primary cats so he will need a tune to suppress it.
I was surprised, removing the primary cats didn't smell at all, in normal driving.

But yeah, unless you like driving around with a CEL, you'll need a tune.
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      02-27-2012, 04:05 PM   #10
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Quote:
Originally Posted by keikdasneak View Post
So leave the OEM exhaust alone and just remove the Primary cats correct?

Thanks guys.
Yes, or change the mufflers in addition to going catless
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      02-27-2012, 04:30 PM   #11
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Question

Quote:
Originally Posted by tibra1 View Post
No way.. dont believe that..any time you remove primary cats on "any" car you will have more smell..maybe leaving secondary cats in there would help..but only when they build enough heat in them..also OP needs to know he will get CEL by removing primary cats so he will need a tune to suppress it.
No clue why you would speak with such conviction when you seem to not have any actual personal experience with a primary cat delete on the m3?

Personal experience > internet theory

I have experience with it, no smell. Bottom line.
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      02-27-2012, 04:46 PM   #12
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when i had my primary deleted, it did smell but not a lot, mostly on morning start up...so saying that no smell its not true... it will smell its just not as crazy as when you take all the cats off... driving of course you cant smell shit.... although i can smell it very faint but its there... so yes its an on and off thing... you smell it some days and some days you dont... my experience...
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      02-27-2012, 05:01 PM   #13
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takign out primaries only smell at cold start-ups and even then the smell isn't enough to bother you. you wont smell nothing during normal driving.

my vote is do the primary cat delete then save money for a real cat back.
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      02-27-2012, 05:02 PM   #14
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I have Turner Test pipes with the OEM exhaust mod and everyone says they love the way my car sounds, me on the other hand, I don't like it. Someone said drone which i actually think it doesn't drone much at all, but it is raspy. Will be changing the axle back soon when i take the car out of winter storage. If you want to stay fairly cheap go with turner test pipes and a megan racing exhaust.
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      02-27-2012, 05:13 PM   #15
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Quote:
Originally Posted by KennyPowers View Post
No clue why you would speak with such conviction when you seem to not have any actual personal experience with a primary cat delete on the m3?

Personal experience > internet theory

I have experience with it, no smell. Bottom line.
I have had full catless 335..full catless VWs..full catless Mitsubishis..are you gonna tell me there is something inherently different on the M3?..Is it not an internal combustion engine with exhaust emissions ..you are misleading the OP by saying there is no smell by removing primary cats..and what may be no smell to you maybe a smell to others there is some subjectivity there...but to say there is no smell is "coooough" bullshit
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      02-27-2012, 05:26 PM   #16
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Quote:
Originally Posted by tibra1 View Post
I have had full catless 335..full catless VWs..full catless Mitsubishis..are you gonna tell me there is something inherently different on the M3?..Is it not an internal combustion engine with exhaust emissions ..you are misleading the OP by saying there is no smell by removing primary cats..and what may be no smell to you maybe a smell to others there is some subjectivity there...but to say there is no smell is "coooough" bullshit
The oem x pipe has 4 cats. 2 400 cell and 2 200 cell.

Primary cat delete refers to the primary 400 cell cats.

The system in this configuation cannt be compared to a fully catless setup on any car.
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      02-28-2012, 10:04 AM   #17
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Not to thread jack, but will deleting just the primary cats make the car a lot raspier? Much louder or only a little compared with an axle back exhaust? And drones a lot more or a little bit? I'm sure these questions would help the OP as well.
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      02-28-2012, 11:18 AM   #18
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I was curious on the sound as well with just a primary cat delte and all else stock.
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      02-28-2012, 01:04 PM   #19
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Quote:
Originally Posted by StephenWatch View Post
It sounds like a shitty 2-stroke dirt bike. Trust me, I had this setup for about 10min before I decided to put the car back on the lift and change it up.
are you a parrot?
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      02-28-2012, 01:21 PM   #20
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Quote:
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are you a parrot?
The worst part is that I have never had just a primary delete and cant comment on the sound! lol
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      02-28-2012, 02:01 PM   #21
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The worst part is that I have never had just a primary delete and cant comment on the sound! lol
This guy copied exactly what you wrote and pasted it. Primaries and oem exhaust mod to me is too raspy. People say my car sounds like american muscle with it. I'm changing it.
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      02-28-2012, 02:12 PM   #22
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Here are the links to the only videos i have of my car with the Primaries deleted and oem exhaust mod. Not great.



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