Catless exhaust system = yellow stuff?

///M Pow3r · 07-01-2009, 02:47 PM

I saw in another thread that a few people with catless exhaust systems get a yellowish residue on the back of their cars.

Can anyone elaborate on this? What is it? How hard is it to clean off? Is it bad for the paint? How long does it take before you need to wash it off, ie. is the build-up noticeable after a few days or a few weeks? Where exactly does it accumulate? Is it underneath the rear bumper or around the back of it also? Thanks!

!Xoible · 07-01-2009, 02:59 PM

probably neighbor's dog peeing. /thread

Nawaaz · 07-01-2009, 03:52 PM

Quote:

Originally Posted by ///M Pow3r

I saw in another thread that a few people with catless exhaust systems get a yellowish residue on the back of their cars.

Can anyone elaborate on this? What is it? How hard is it to clean off? Is it bad for the paint? How long does it take before you need to wash it off, ie. is the build-up noticeable after a few days or a few weeks? Where exactly does it accumulate? Is it underneath the rear bumper or around the back of it also? Thanks!

Probably the exhaust heat from the exhaust itself caused that. You can't clean it off since it's basically burned. You probably should get a bumper shield that protects those areas from the extreme heat.

///M Pow3r · 07-01-2009, 04:25 PM

I don't have a catless exhaust, but I saw another guy say his local carwash used some special spray to wash it off. I wonder what it is

!Xoible · 07-01-2009, 04:35 PM

well your cats are a place that offers an environment for certain chemical reactions to happen. the cats themselves have chemicals that allow reaction with the toxic chemicals coming into them, to make them less toxic.

i can imagine if there's no cats -> there's no chemicals to tame down what enters them -> that yellow stuff is some nasty ass toxic chemicals. dont touch that shit

m34jlp · 07-01-2009, 05:04 PM

I dont think there is any noticeable increase in heat from removing cats. It is probably the exhaust gases that are dirtier and stick to the bumper. i wash my rear bumper often to avoid the yellowing, but i hope someone can chime in on a solution to clean it when it does turn yellow.

m34jlp · 07-01-2009, 05:09 PM

maybe clearbra the area around the exhaust tips...

Space Ghost · 07-01-2009, 05:23 PM

on space grey no yellow 3+ months

m34jlp · 07-01-2009, 05:26 PM

look closely...i hadnt even noticed on my white until i saw this post...its not too bad but if you let it build up it is very tough to get off (trust me)

MrHarris · 07-01-2009, 06:39 PM

So what chemical/method do you use/do to get the yellow stuff off?

m34jlp · 07-01-2009, 07:41 PM

usually with soap and water it comes off with alittle knuckle behind it...believe or not i have also tried the bug remover and it works great as well...i am not sure if its the best for the paint but it works

///M Pow3r · 07-01-2009, 10:54 PM

Quote:

Originally Posted by !Xoible

well your cats are a place that offers an environment for certain chemical reactions to happen. the cats themselves have chemicals that allow reaction with the toxic chemicals coming into them, to make them less toxic.

i can imagine if there's no cats -> there's no chemicals to tame down what enters them -> that yellow stuff is some nasty ass toxic chemicals. dont touch that shit

Haha yeah I'm pretty sure it's some kind of toxic crap since it's pretty much unfiltered through cats, but I was wondering if anyone knew exactly.

///M Pow3r · 07-01-2009, 10:55 PM

Quote:

Originally Posted by m34jlp

look closely...i hadnt even noticed on my white until i saw this post...its not too bad but if you let it build up it is very tough to get off (trust me)

Is it a kind of film? Or a stain? Would you mind posting a pic, or can you describe exactly where it built up?

jimmyeatsworld · 07-02-2009, 02:12 AM

I don't see any residue on mine. Albeit I have a VRS diffuser, and I do not notice it on there.

I have a yellowish tint on my exhaust tips. A little polish will take that out.

m34jlp · 07-02-2009, 02:38 PM

Quote:

Originally Posted by ///M Pow3r

Is it a kind of film? Or a stain? Would you mind posting a pic, or can you describe exactly where it built up?

will do when it builds up again i'll snap a pic

///M Pow3r · 07-02-2009, 03:01 PM

Quote:

Originally Posted by m34jlp

will do when it builds up again i'll snap a pic

Cool thanks

tightie · 07-02-2009, 03:41 PM

nothing happens to your car, i didnt wash it for over a month. im catless + supercharged. you just have to use soap/water.

///M Pow3r · 07-02-2009, 03:48 PM

Quote:

Originally Posted by tightie

nothing happens to your car, i didnt wash it for over a month. im catless + supercharged. you just have to use soap/water.

Good to know, thanks

MWorldorder · 07-02-2009, 04:16 PM

It only happened to me the first week. Then it never happened again.

M3 Montreal · 07-02-2009, 06:37 PM

Quote:

Originally Posted by m34jlp

I dont think there is any noticeable increase in heat from removing cats. It is probably the exhaust gases that are dirtier and stick to the bumper. i wash my rear bumper often to avoid the yellowing, but i hope someone can chime in on a solution to clean it when it does turn yellow.

+1

The yellow builds up over time. On a white car it shows a lot and it's the entire back that builds the yellow but it's most evident on the bumper since it's right next to the exhaust.

It was me that posted about my local car wash cleaning it WAY easier than when I tried it. Next time I'll ask them what they used.

It probably only shows on the AW only. No big deal and NO it's not extra heat burning your paint ! It takes about a month of buildup before it gets really bad.

dcstep · 07-02-2009, 07:01 PM

Just fyi, the cats add heat that burns off unburned gas and changes the chemical makeup of the exhaust. Removing the cats allows more of the engine residue to excape out the exhaust. That residue is probably what you're seeing. It's NOT burning the paint, but you do need to clean it off regularly.

Dave

NFDoms2k1 · 07-02-2009, 08:37 PM

I think I posted this somewhere else, but a mild solvent works well (acetone applied lightly takes it right off), or if the car has a good layer of wax on it most liquid cleaning polishes will take it right off, while at the same time protecting it.

For the tips any good metal polisher will give those things a brand new look with a little elbow grease - I wish I had the stuff in front of me and I can't remember the name of it off the top of my head but there is one out there I started using my friend turned me onto that protects specifically against tars and carbon residues, so its perfect for the exhaust (just requires much less work to get the tips that brilliant shine afterwards)

07-01-2009, 02:47 PM	#1
///M Pow3r Private 9 Rep 99 Posts Drives: 09 E92 M3 Join Date: Oct 2008 Location: El Paso, Texas iTrader: (0)	Catless exhaust system = yellow stuff? I saw in another thread that a few people with catless exhaust systems get a yellowish residue on the back of their cars. Can anyone elaborate on this? What is it? How hard is it to clean off? Is it bad for the paint? How long does it take before you need to wash it off, ie. is the build-up noticeable after a few days or a few weeks? Where exactly does it accumulate? Is it underneath the rear bumper or around the back of it also? Thanks! __________________ Rated ///M
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07-01-2009, 02:59 PM	#2
!Xoible Banned 837 Rep 46,029 Posts Drives: .... Join Date: Nov 2006 Location: . iTrader: (4) Garage List 2008 M3 [4.00] 2007 335i [9.00] 2008 528i [8.00] 2006 Infiniti - G35 ... [8.00]	probably neighbor's dog peeing. /thread
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07-01-2009, 04:25 PM	#4
///M Pow3r Private 9 Rep 99 Posts Drives: 09 E92 M3 Join Date: Oct 2008 Location: El Paso, Texas iTrader: (0)	I don't have a catless exhaust, but I saw another guy say his local carwash used some special spray to wash it off. I wonder what it is __________________ Rated ///M
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07-01-2009, 04:35 PM	#5
!Xoible Banned 837 Rep 46,029 Posts Drives: .... Join Date: Nov 2006 Location: . iTrader: (4) Garage List 2008 M3 [4.00] 2007 335i [9.00] 2008 528i [8.00] 2006 Infiniti - G35 ... [8.00]	well your cats are a place that offers an environment for certain chemical reactions to happen. the cats themselves have chemicals that allow reaction with the toxic chemicals coming into them, to make them less toxic. i can imagine if there's no cats -> there's no chemicals to tame down what enters them -> that yellow stuff is some nasty ass toxic chemicals. dont touch that shit
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07-01-2009, 05:04 PM	#6
m34jlp Wheel Whore 156 Rep 937 Posts Drives: 2015 AY F82 M4 Join Date: Nov 2008 Location: Miami, Fl iTrader: (0)	I dont think there is any noticeable increase in heat from removing cats. It is probably the exhaust gases that are dirtier and stick to the bumper. i wash my rear bumper often to avoid the yellowing, but i hope someone can chime in on a solution to clean it when it does turn yellow.
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07-01-2009, 05:09 PM	#7
m34jlp Wheel Whore 156 Rep 937 Posts Drives: 2015 AY F82 M4 Join Date: Nov 2008 Location: Miami, Fl iTrader: (0)	maybe clearbra the area around the exhaust tips...
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07-01-2009, 05:23 PM	#8
Space Ghost Captain 11 Rep 619 Posts Drives: E92 M3 Join Date: Aug 2008 Location: USA-PA iTrader: (5)	Catless on space grey no yellow 3+ months
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07-01-2009, 05:26 PM	#9
m34jlp Wheel Whore 156 Rep 937 Posts Drives: 2015 AY F82 M4 Join Date: Nov 2008 Location: Miami, Fl iTrader: (0)	look closely...i hadnt even noticed on my white until i saw this post...its not too bad but if you let it build up it is very tough to get off (trust me)
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07-01-2009, 06:39 PM	#10
MrHarris yodog 197 Rep 5,025 Posts Drives: '86 Corolla Join Date: Jun 2007 Location: Diamond Bar, Ca iTrader: (5) Garage List 2009 BMW [10.00]	So what chemical/method do you use/do to get the yellow stuff off? __________________ 2009 E92 M3 \| Alpine White \| Black Extended \| Advan RS \| Turner Test Pipes \| Dinan Axle-Back \| OETuning \| Eibach Springs \| UUC SSK \| VRS Front Lip \| VRS Type I Diffuser \| Matte Black \| RPi Scoops \| MS Filter \| Yokohama AD08 \| F1 Pinnacle Special Thanks: Gintani \| OETuning \| eAs
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07-01-2009, 07:41 PM	#11
m34jlp Wheel Whore 156 Rep 937 Posts Drives: 2015 AY F82 M4 Join Date: Nov 2008 Location: Miami, Fl iTrader: (0)	usually with soap and water it comes off with alittle knuckle behind it...believe or not i have also tried the bug remover and it works great as well...i am not sure if its the best for the paint but it works
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07-02-2009, 02:12 AM	#14
jimmyeatsworld Second Lieutenant 7 Rep 213 Posts Drives: 2008 E92 M3 6MT Join Date: Nov 2008 Location: Orange County iTrader: (0)	I don't see any residue on mine. Albeit I have a VRS diffuser, and I do not notice it on there. I have a yellowish tint on my exhaust tips. A little polish will take that out. __________________ RPI GT Race Exhaust ~ RPI Scoops ~ BMC Air Filter ~ 19" BBS LM DBK ~ JL Motoring VRS Front Lip ~ Vorsteiner Diffuser Type I ~ KW Clubsports My RPI GT Race Dyno vs. Stock: http://www.m3post.com/forums/showthread.php?t=239228
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07-02-2009, 03:41 PM	#17
tightie JOSH SHOKRI. 524 Rep 5,881 Posts Drives: 991 GT3RS, 964, Raptor Join Date: Aug 2005 Location: los angeles, california. iTrader: (7) Garage List 2008 BMW M3 [7.90]	nothing happens to your car, i didnt wash it for over a month. im catless + supercharged. you just have to use soap/water. __________________ Current: 16 991 GT3RS , 91 964 C2, 17 Raptor \| Past: 2015 991 GT3, 2015 i3,15 YMB F80 M3, 13 E92 M3 DCT, 08 E92 M3 6MT, 07 E60 M5, 02 E46 M3 Instagram: @josh_speeddistrict #SpeedDistrict @SpeedDistrict
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07-02-2009, 04:16 PM	#19
MWorldorder Second Lieutenant 10 Rep 296 Posts Drives: M4 Join Date: Apr 2008 Location: L.A. iTrader: (0)	It only happened to me the first week. Then it never happened again.
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07-02-2009, 07:01 PM	#21
dcstep Major General 1291 Rep 7,389 Posts Drives: '09 Cpe Silverstone FR 6MT Join Date: Nov 2008 Location: Colorado iTrader: (0) Garage List 2009 M3 [8.40]	Just fyi, the cats add heat that burns off unburned gas and changes the chemical makeup of the exhaust. Removing the cats allows more of the engine residue to excape out the exhaust. That residue is probably what you're seeing. It's NOT burning the paint, but you do need to clean it off regularly. Dave __________________ Flickr Photos Ucm, Inc.
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07-02-2009, 08:37 PM	#22
NFDoms2k1 Private First Class 9 Rep 167 Posts Drives: Cute Little Convertible Join Date: Feb 2009 Location: New York iTrader: (3)	I think I posted this somewhere else, but a mild solvent works well (acetone applied lightly takes it right off), or if the car has a good layer of wax on it most liquid cleaning polishes will take it right off, while at the same time protecting it. For the tips any good metal polisher will give those things a brand new look with a little elbow grease - I wish I had the stuff in front of me and I can't remember the name of it off the top of my head but there is one out there I started using my friend turned me onto that protects specifically against tars and carbon residues, so its perfect for the exhaust (just requires much less work to get the tips that brilliant shine afterwards) __________________ '09 E93 M3, AW, M-DCT, Fully Loaded Bunch of mods, why such limited signature space M3post ?
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