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When did de-cat's become an MOT fail?

Will G-J

Nurburgring
Joined
8 Jun 2006
Messages
450
What's the latest year you can de-cat and pass MOT?

Cheers

W


Migration info. Legacy thread was 116875
 
1st August 1992 is the date the cat requirement came in. Any car before this does not require one.


Ian.


Migration info. Legacy thread was 116887
 
Ok cheers Ian

So what would a de-cat do to my car? wrt noise (for trackdays) and bhp? Anything or nothing?

W


Migration info. Legacy thread was 116915
 
Ok i'm a little more confused now.

In my searching I have found Cup pipes, G pipes and cat bypass pipes! Am I right in thinking that these all just bypass different parts of the exhaust system?

So if i'm after a slightly deeper, throatier sound without failing noise tests and maybe with a few extra bhp which do I want?

W


Migration info. Legacy thread was 116937
 
Not sure about the 'g pipes' but afaik the cat bypass is as it sounds and the cup pipes are silencer bypasses in that they exit to tailpipe directly from the cats. I've a pair of these for my car but have yet to fit - expect noise from hell. Cat bypass will also increase noise and release a few bhp. Cat bypass should be ok for noise regs (guess) but silencer bypass probably tip you over. Believe that my GT3 with them on was around 108db static.

Cat bypass + silencer bypass = one unholy angry barking mad 911 (sweeeeet!) but will make your ears bleed!


Migration info. Legacy thread was 116941
 
lol

thanks for that I guess cat bypass it is then

Can I do it myself?


Migration info. Legacy thread was 116942
 
When I was driving BMWs a number of friends had them de-catted and they passed the MOT. I think as long as the emissions were passed then it was OK. I am sure if the MOT guy knew thwn he would fail it. However-how closely do they look?

So it seems some pass with no cat and some fail????


Migration info. Legacy thread was 116943
 
The cats are right at the back of the engine basically up at the bumper if i'm not mistaken so should be reasonably accessible. Trouble with exhaust bits is always the clips and associated bolts.

Get the car jacked up and have a scope out first, giving all fastners a good going over with plus gas or atleast wd40 - trust me, it's worth it later! Then when your bits arrive the bolts should be marginally more compliant. Failing that it'll be a fun day with the junior hacksaw!

To summarise, not a technically difficult job at all but has high potential to be a labour intensive nightmare.


Migration info. Legacy thread was 116944
 
Well i'm going to have some stuff done at 9m anyway so i might just ask them to stick it on for me.

W


Migration info. Legacy thread was 116947
 
Three bits to a 964 exhaust in order of engine to outlet - 1 cat, 2 primary silencer across the back, 3 secondary silencer under rear wing. Cat bypass removes 1. Cup pipe removes 2. G-Pipe removes 3.

You can do any combination. Each gives different sound and noise level. Don't know the noise level for each combination except do all three and you'll quickly go deaf.

Ian.


Migration info. Legacy thread was 116959
 
I have a cat bypass and primary silencer bypass. Its prob just below 105db mark so adding the g pipe (secondary silencer bypass) would be mental loud!

Migration info. Legacy thread was 116971
 
Previous poster said:
Quote: Originally posted by ian_uk on 13 February 2007

Three bits to a 964 exhaust in order of engine to outlet - 1 cat, 2 primary silencer across the back, 3 secondary silencer under rear wing. Cat bypass removes 1. Cup pipe removes 2. G-Pipe removes 3.

You can do any combination. Each gives different sound and noise level. Don't know the noise level for each combination except do all three and you'll quickly go deaf.

Ian.



So is a G-pipe also just known as a sports exhaust?

Migration info. Legacy thread was 117273
 
OK, ignore what I asked above. A bit of research shows that the G-pipe is just a bypass of the final silencer.

Does anybody have any thoughts of which is best; a G-pipe or a Sports silencer? Which of these is more track friendly (passes noise testing)?

TIA.


Migration info. Legacy thread was 117344
 

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