Decat the Z4M..

JB 007 · 07-08-2010, 01:40 AM

What happens when I decat my Z4M? Any loss hp? More sound? I want more than my Hayward&Scott back boxes...
Thanks

Z4-VILLA · 07-08-2010, 01:47 AM

youre gonna need software no doubt...

JB 007 · 07-08-2010, 01:54 AM

Quote:

Originally Posted by Z4-Villalona

youre gonna need software no doubt...

Really?

JCz04Bimmer · 07-08-2010, 03:51 PM

The US-spec cars have two pairs of catalytic converters. One in the header section. One in the s-pipe section. Removing the cats in the s-pipe section (aka section 1) results in no warning lights (since there are no sensors in there) and is a good modification. It deepens the exhaust note a bit and probably adds a pair of horses. Nothing major. Removal of the cats from the header section, however, will require you to address some check engine lights since there are O2 sensors before and after.

Not sure how the Euro-spec car is setup, but I believe they only have the cats in the header section and thus removal will cause a check engine light.

Juice84 · 07-08-2010, 04:34 PM

Quote:

Originally Posted by JCz04Bimmer

Not sure how the Euro-spec car is setup, but I believe they only have the cats in the header section and thus removal will cause a check engine light.

I think you got it backwards... the euro-spec only have the second set of cats with the 02 sensor behind them. This is why euro headers only have 1 o2 sensor bung.

JB 007 · 07-09-2010, 05:02 AM

Thanks for all for your kind comments..

ga41 · 07-09-2010, 05:22 AM

Do it! Then we can compare sounds, RPI vs H&S with no catalytic converters!

JB 007 · 08-02-2010, 02:33 AM

Quote:

Originally Posted by ga41

Do it! Then we can compare sounds, RPI vs H&S with no catalytic converters!

Are you decat your Z4M?

ga41 · 08-02-2010, 02:46 AM

Quote:

Originally Posted by JB 007

Are you decat your Z4M?

Not planning to at the moment. My O2 sensors already failed once and i think they're starting to go again so i dont want to make the situation worse! Do you have any problems with yours?

ZM4000 · 08-02-2010, 03:42 AM

do u have a lot of problems with your sensor ga41?? Never had a problem since i got the new exhaust

ga41 · 08-02-2010, 04:06 AM

Yea i do. I changed them a few months ago and i'm already starting to get sporadic error messages about them...

Probably because it's a UK car running on rubbish Cyprus petrol.

JB 007 · 08-02-2010, 04:25 AM

Quote:

Originally Posted by ga41

Yea i do. I changed them a few months ago and i'm already starting to get sporadic error messages about them...

Probably because it's a UK car running on rubbish Cyprus petrol.

No chance for the errors...

If you can see north sides petrols you can thanks for your petrol stations..

I buy the petrol from south for my cars...

lucid · 08-02-2010, 08:09 AM

Quote:

Originally Posted by JB 007

What happens when I decat my Z4M?

You will increase your emissions drastically for a mere 10-20hp that you won't even feel and a louder exhaust that you can probably achieve through other means.

ZM4000 · 08-02-2010, 08:16 AM

lucky me then.

F360C · 08-02-2010, 05:55 PM

Quote:

Originally Posted by lucid

You will increase your emissions drastically for a mere 10-20hp that you won't even feel and a louder exhaust that you can probably achieve through other means.

Although I do agree you are increasing emissions it is for sure a gain you can feel. When I dynoed my car I put out 306whp and that same day two e46 m3s with only cat back exhausts on them out out only 278-280whp. Thats a soild 26 wheel horsepower gain over a stock s54! You can def feel that! I also still have the secondary cats in place so I am still controlling emissions a bit. Now my question is do you run cats on your e30 m3 race car?

lucid · 08-02-2010, 08:07 PM

Quote:

Originally Posted by F360C

Although I do agree you are increasing emissions it is for sure a gain you can feel. When I dynoed my car I put out 306whp and that same day two e46 m3s with only cat back exhausts on them out out only 278-280whp. Thats a soild 26 wheel horsepower gain over a stock s54! You can def feel that! I also still have the secondary cats in place so I am still controlling emissions a bit. Now my question is do you run cats on your e30 m3 race car?

Yes, I do have cats on my E30 M3. VSR center section with high flow cats. Certain classes require them. I wouldn't be opposed if all classes did. (I don't club race, but I do time trials).

However, the extra 5%-10% power bump would actually matter in a race whereas it is very close to meaningless on the street. Like all trade-offs, one has to consider what one is trying to accomplish when considering the costs/benefits.

Anyway, we can debate how well you can feel the 5%-10% bump in power. The majority of M owners wouldn't be able to tell in a blind test.

The point is, even if you are the kind of person who can feel it, it will be rather subtle and pretty much pointless on the street. And, you wouldn't be increasing emissions by 5%-10% in return. It is way worse than that. Hard to pin that down as it depends on the specifics of the engine and its operation, but we are talking about orders of magnitude worse. Removing the cats is a horrible trade-off for street driving. Not to mention that it is illegal in most states.

Juice84 · 08-02-2010, 08:21 PM

Wow a green performance car guy... thats almost like finding a unicorn.

Diokaef · 08-03-2010, 12:18 AM

My race car had cats right before the mufflers with 100 cell and my exhaust has always being wrapped to keep the speed flow and enough heat so the cat would work. with high temperature exhaust a 100 cell cat can perform very close to a 200 cell's one in terms of emissions and still give you high performance.

07-08-2010, 01:40 AM	#1
JB 007 First Lieutenant 44 Rep 380 Posts Drives: Z4MC RRS MINI... Join Date: Apr 2009 Location: Nicosia iTrader: (0)	Decat the Z4M.. What happens when I decat my Z4M? Any loss hp? More sound? I want more than my Hayward&Scott back boxes... Thanks __________________ Z4MC_Black Sapphire/Imola-_-DMS ECU ll H&S cat-back ll H&R coilovers ll CF Lip ll Lamin-X ll Matte black kidneys ll Afe drop in ll Afe intake elbow ll RPi scoop ll LeatherZ imola shift boot ll ZHP knob...
	Appreciate 0 Tweet Quote

07-08-2010, 01:47 AM	#2
Z4-VILLA Banned 111 Rep 2,460 Posts Drives: Z4M Hardtop Roadster Join Date: Feb 2009 Location: Classified iTrader: (0)	youre gonna need software no doubt...
	Appreciate 0 Quote

07-08-2010, 03:51 PM	#4
JCz04Bimmer Captain 31 Rep 606 Posts Drives: 06 Z4MC Join Date: Feb 2008 Location: New York City iTrader: (2)	The US-spec cars have two pairs of catalytic converters. One in the header section. One in the s-pipe section. Removing the cats in the s-pipe section (aka section 1) results in no warning lights (since there are no sensors in there) and is a good modification. It deepens the exhaust note a bit and probably adds a pair of horses. Nothing major. Removal of the cats from the header section, however, will require you to address some check engine lights since there are O2 sensors before and after. Not sure how the Euro-spec car is setup, but I believe they only have the cats in the header section and thus removal will cause a check engine light. __________________ \|www.onehotlap.com\|Real People\|Real Cars\|
	Appreciate 0 Quote

07-09-2010, 05:02 AM	#6
JB 007 First Lieutenant 44 Rep 380 Posts Drives: Z4MC RRS MINI... Join Date: Apr 2009 Location: Nicosia iTrader: (0)	Thanks for all for your kind comments.. __________________ Z4MC_Black Sapphire/Imola-_-DMS ECU ll H&S cat-back ll H&R coilovers ll CF Lip ll Lamin-X ll Matte black kidneys ll Afe drop in ll Afe intake elbow ll RPi scoop ll LeatherZ imola shift boot ll ZHP knob...
	Appreciate 0 Quote

07-09-2010, 05:22 AM	#7
ga41 Lieutenant 31 Rep 503 Posts Drives: Z4 M Coupe Join Date: Jun 2009 Location: Paphos iTrader: (0) Garage List 2006 Z4 M Coupe [0.00]	Do it! Then we can compare sounds, RPI vs H&S with no catalytic converters! __________________
	Appreciate 0 Quote

08-02-2010, 03:42 AM	#10
ZM4000 Private First Class 9 Rep 123 Posts Drives: Z4M Join Date: Jun 2010 Location: Luxembourg iTrader: (0)	do u have a lot of problems with your sensor ga41?? Never had a problem since i got the new exhaust
	Appreciate 0 Quote

08-02-2010, 04:06 AM	#11
ga41 Lieutenant 31 Rep 503 Posts Drives: Z4 M Coupe Join Date: Jun 2009 Location: Paphos iTrader: (0) Garage List 2006 Z4 M Coupe [0.00]	Yea i do. I changed them a few months ago and i'm already starting to get sporadic error messages about them... Probably because it's a UK car running on rubbish Cyprus petrol. __________________
	Appreciate 0 Quote

08-02-2010, 08:16 AM	#14
ZM4000 Private First Class 9 Rep 123 Posts Drives: Z4M Join Date: Jun 2010 Location: Luxembourg iTrader: (0)	lucky me then.
	Appreciate 0 Quote

08-02-2010, 08:21 PM	#17
Juice84 Second Lieutenant 9 Rep 238 Posts Drives: '03 2.5i Z4 Join Date: Oct 2009 Location: Wisconsin iTrader: (0)	Wow a green performance car guy... thats almost like finding a unicorn.
	Appreciate 0 Quote

08-03-2010, 12:18 AM	#18
Diokaef Engineer 212 Rep 2,122 Posts Drives: M235I 2015, 335i 2011 Join Date: Dec 2009 Location: TAMPA FL iTrader: (17) Garage List 2008 Z4M Coupe [6.33]	My race car had cats right before the mufflers with 100 cell and my exhaust has always being wrapped to keep the speed flow and enough heat so the cat would work. with high temperature exhaust a 100 cell cat can perform very close to a 200 cell's one in terms of emissions and still give you high performance.
	Appreciate 0 Quote