Cat Delete on a 2.8 Z3

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BryZzz
Joined: Sun 20 Oct, 2013 01:56
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  Z3 roadster 2.8

Cat Delete on a 2.8 Z3

Post by BryZzz » Fri 03 Jan, 2014 02:08

Hi guys, thinking of taking my cat out and replacing it with a resonator or a 2.5 inch straight pipe. Has anyone tried doing this? Btw, im sporting an axle back magnaflow replica. Don't want to get too loud and drown IN DRONE.

Thanks!

Julie Z3
Joined: Mon 22 Nov, 2010 09:47
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  Z3 roadster 2.8
Location: Bristol

Re: Cat Delete on a 2.8 Z3

Post by Julie Z3 » Mon 06 Jan, 2014 18:00

Mine is catless with a stainless rear box (unknown make) and it's pretty loud, would really like a standard system but too expensive for my tastes! You'll also need a friendly MOT tester :)

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Deano1712
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Re: Cat Delete on a 2.8 Z3

Post by Deano1712 » Mon 06 Jan, 2014 20:53

My car doesn't have a normal engine in it, but I can say with and without CATs is like night and day for noise. Without my car was twice as loud as it is now. Im sticking with the CATs fitted for now while my ears recover.
Z3M with a few mods...and a little bit more power

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sirius-c
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  Z3 roadster 2.8
Location: Eeh ba gum lad, 'ow do?

Re: Cat Delete on a 2.8 Z3

Post by sirius-c » Tue 07 Jan, 2014 20:16

Was there any noticeable increase in power with a decat?... as I plan on doing this if its worth it...I'm not planning on a remap though

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t-tony
Joined: Sun 21 Feb, 2010 23:17
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  Z3 roadster 2.0
Location: torksey lock

Re: Cat Delete on a 2.8 Z3

Post by t-tony » Tue 07 Jan, 2014 22:41

Julie Z3 wrote:Mine is catless with a stainless rear box (unknown make) and it's pretty loud, would really like a standard system but too expensive for my tastes! You'll also need a friendly MOT tester :)
What you really need is an M.O.T. tester who says to you bring me the car with the cat still fitted so I can test it properly without risking my livelihood for the sake of your vanity. After the test you can have whatever you want on your car for 12mths on your own conscience not the M.O.T. tester's. The same applies to " doctored " number plates too. Keep your originals and fit them just for the test, afterwards you can have whatever the police let you get away with.
"Knowledge and experience are not always the same"

maurice the martian
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  Z4 roadster 3.0i
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Re: Cat Delete on a 2.8 Z3

Post by maurice the martian » Thu 09 Jan, 2014 14:49

My Z4 has had the secondary cats removed, just passed the mot today , no advisories..
Moz:D

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t-tony
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  Z3 roadster 2.0
Location: torksey lock

Re: Cat Delete on a 2.8 Z3

Post by t-tony » Thu 09 Jan, 2014 15:29

That's not to say it should have. If that particular tester doesn't care that is up to him/her, but just because they don't doesn't make it right. You can go to another test station saying " it passed like this last year" which puts someone else under pressure to do likewise. :head:
"Knowledge and experience are not always the same"

maurice the martian
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  Z4 roadster 3.0i
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Re: Cat Delete on a 2.8 Z3

Post by maurice the martian » Thu 09 Jan, 2014 16:00

Strange thing is in england there are four cats , 2 on the ex manifold and 2 more under the car, yet in the Usa where they have more stringent emission laws the z4 only has 2 cats.
Even with the secondary cats removed it still complies with the mot.emission test.
I watched him test it and he appeared to do a thorough job
M

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t-tony
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  Z3 roadster 2.0
Location: torksey lock

Re: Cat Delete on a 2.8 Z3

Post by t-tony » Thu 09 Jan, 2014 16:23

I wouldn't question that but the failure criteria is if a cat has been removed where you know it was fitted as standard, then the vehicle should fail the test. I don't say I agree with it either but a tester COULD lose their job as a result and in MHO it isn't worth it. The mot testers manual is available to see,and I think ,download on the VOSA website. Having done this job for nearly 40 years I could write a book on some of the contradiction contained in it. Don't start a thread regarding oil temperature for Diesel engine emission testing. That's a whole different can of worms. Glad they don't make diesel Z's.
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Stormy_be
Joined: Thu 19 Dec, 2013 06:43
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by Stormy_be » Thu 09 Jan, 2014 17:12

What i have seen on other vehicles is that people remove everything inside the cat, but leave the same tubes on the car.
From the exterior it looks like the cat is fitted. Not possible to see from an examiner's point of view (unless it completely fails on the emissions test).

Regards, Koen

t-tony
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  Z3 roadster 2.0
Location: torksey lock

Re: Cat Delete on a 2.8 Z3

Post by t-tony » Thu 09 Jan, 2014 17:15

Yes,you are correct there. The same thing will soon happen with DPF .
"Knowledge and experience are not always the same"

maurice the martian
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  Z4 roadster 3.0i
Location: mars

Re: Cat Delete on a 2.8 Z3

Post by maurice the martian » Thu 09 Jan, 2014 17:49

T B H I half expected to get pulled for it, having said that its been done properly and (to me ) it looks like it always been like that.I suppose unless the tester is clued up on Z4 s spec then the missing cats wouldnt be noticed.
Moz

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JamesZ32.8
Joined: Sun 15 Sep, 2013 09:52
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Re: Cat Delete on a 2.8 Z3

Post by JamesZ32.8 » Mon 20 Jan, 2014 10:30

So back onto the subject of de catting is it actually worth doing on a 2.8 ? or is the noise to painful ?

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Southernboy
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Location: Johannesburg

Re: Cat Delete on a 2.8 Z3

Post by Southernboy » Mon 20 Jan, 2014 10:45

a). it is worth doing...the CAT retricts the flow
b). it's no more noisy than with the CAT since the CAT isn't a silencer....so go for it. You can decide if you want more modifications after you remove the CAT.
"Normal is overrated"
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maurice the martian
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  Z4 roadster 3.0i
Location: mars

Re: Cat Delete on a 2.8 Z3

Post by maurice the martian » Mon 20 Jan, 2014 11:34

Quite honestly I was disappointed that it wasnt noisier after doing mine.So im still playing around to get a bit more that wont annoy me on long cruzes.
M

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Southernboy
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Location: Johannesburg

Re: Cat Delete on a 2.8 Z3

Post by Southernboy » Mon 20 Jan, 2014 11:44

A decent back box is what you need to look for after de-catting... If you fool around with the front box you will get "drone"... To get a really decent tone, I would not recommend Stainless Steel boxes. They always sound kind of "tinny"... Have a chat to some professional exhaust guys in your area and explain what you want to achieve and get their advice.(hopefully it's free)... Bear in mind that as the system heats up while driving, the "note" will lower to a deeper base note. Using a larger diameter pipe will help flow, but again, it requires some professional design work to ensure the exhaust also assists in the extraction of the gasses. What you want is a slightly louder 6 cylinder "purr" not the racket of a pimp-mobile...:wink:
"Normal is overrated"
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BryZzz
Joined: Sun 20 Oct, 2013 01:56
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by BryZzz » Mon 12 Jan, 2015 09:05

Just to update you guys,

I took out the resonator, did a straight pipe out to the VAREX muffler that I installed.

Here are some pics and the soundclip

Soundclip:
https://www.youtube.com/watch?v=aUdy7b1AukA

Image
Image

sviru
Joined: Wed 06 Apr, 2011 22:32
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by sviru » Wed 14 Jan, 2015 14:48

that is a pretty nice sound!
Image

BryZzz
Joined: Sun 20 Oct, 2013 01:56
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by BryZzz » Fri 23 Jan, 2015 10:40

thanks sviru!

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sirius-c
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  Z3 roadster 2.8
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Re: Cat Delete on a 2.8 Z3

Post by sirius-c » Fri 23 Jan, 2015 11:01

Nice, the first 17 seconds sound like an angry lion :D

I'm not familiar with a VAREX muffler, how does that work? it certainly makes a huge difference between modes
1997 2.8L Z3 Roadster

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Designed or not designed, that is the question.

bazza1966
Joined: Thu 21 Nov, 2013 10:09
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by bazza1966 » Sat 24 Jan, 2015 08:53

That's a beautiful sound where are they based? and price? maybe in the market for that as my exhaust will need replacing shortly. :(
Bazza (East Dorset)

BryZzz
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by BryZzz » Mon 26 Jan, 2015 09:21

sirius-c wrote:Nice, the first 17 seconds sound like an angry lion :D

I'm not familiar with a VAREX muffler, how does that work? it certainly makes a huge difference between modes
Hi,

The muffler has a butterfly inside which you can electronically control, for days when you just feel like driving crazy aggressive with a growl or days when you just want your car to sound stock.

They're distributed by xforce exhaust, australia and the U.S.... I love how it sounds... I have the same exhaust in my M... love it! :D

BryZzz
Joined: Sun 20 Oct, 2013 01:56
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  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by BryZzz » Mon 26 Jan, 2015 09:25

Here it is on the M. Still need to take the resonator out..
https://www.youtube.com/watch?v=vlhPnGk68vE

I sold my silver 2.8, the new owner loves the exhaust! hehe

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sirius-c
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  Z3 roadster 2.8
Location: Eeh ba gum lad, 'ow do?

Re: Cat Delete on a 2.8 Z3

Post by sirius-c » Mon 26 Jan, 2015 13:52

bah, its a shame I've just had all mine replaced, i would have had a look into buying one of these varex types...
Oh well, i do like my new s.s exhaust and sports cat etc although its always in loud mode :D
1997 2.8L Z3 Roadster

Image

Designed or not designed, that is the question.

BryZzz
Joined: Sun 20 Oct, 2013 01:56
Posts: 19

  Z3 roadster 2.8

Re: Cat Delete on a 2.8 Z3

Post by BryZzz » Wed 28 Jan, 2015 08:18

sirius-c wrote:bah, its a shame I've just had all mine replaced, i would have had a look into buying one of these varex types...
Oh well, i do like my new s.s exhaust and sports cat etc although its always in loud mode :D
It's always a treat to drive in loud mode! haha :D

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