Questions on decatting UK!

L

Lukie761

Member
Hi guys,

I'm very excited to be having a custom exhaust system made and fitted this coming Saturday, however I have some questions that I really need answering to make my decisions...
1.UK exhaust spec, are there cats in both the manifold and under the car?
2.if so, does removal of the cats under the car give mot failure.
3.what set-ups have you guys done? Anyone gone decat straight through to backbox? Thoughts on it?

I'm really stuck guys, I think decat straight through to backbox would be awesome, I just need to know the potential issues and almost have some clarity.

Any helpful answers are greatly appreciated!!

Luke
 
Lukie761 said:
Cheers ryan, don't they do a visual inspection for cats however?
Click to expand...


There is a visual inspection for the secondary cat, the primrary is down to the emissions test which it won't pass if removed!
 
I was just looking into decats. Does anyone know if there is a bolt on kit or is it just a matter of getting one fabricated?
 
Nautrey said:
I was just looking into decats. Does anyone know if there is a bolt on kit or is it just a matter of getting one fabricated?
Click to expand...

The way I have done mine is by removing from the car, carefully removing the heatshield and then opening up the cat with the plasma. I then gutted them before welding up and replacing the heatshield. As a result, my car looks standard underneath and no problems with the mot. As mentioned, if the cats are visibly missing, it is a fail.

Mine pops and crackles like a good'un now though 😃 It also feels like it's been remapped, the increase in power and throttle response is THAT noticeable.

Mike
 
As a matter of interest re the above advice that removal of the secondary Cat is not an MOT fail in itself, the MOT test manual for petrol engined cars first used after 2002 and listed in the database (which the Z4 is) seems to say it should be a fail,

"Reason for rejection 3. A catalytic converter or particulate filter missing where one was fitted as standard "

https://www.mot-testing.service.gov.uk/documents/manuals/m4s07000101.htm

https://www.mot-testing.service.gov.uk/documents/manuals/m4s07000311.htm

Whether you can get away with it is a different question but it looks like it should be fail, unless I'm reading it wrong? :?
 
Has anyone dyno tested before/after (or even a timed 0 - 60) with this rather appealing cat gutting exercise?
 
Ducklakeview said:
Nautrey said:
I was just looking into decats. Does anyone know if there is a bolt on kit or is it just a matter of getting one fabricated?
Click to expand...

The way I have done mine is by removing from the car, carefully removing the heatshield and then opening up the cat with the plasma. I then gutted them before welding up and replacing the heatshield. As a result, my car looks standard underneath and no problems with the mot. As mentioned, if the cats are visibly missing, it is a fail.

Mine pops and crackles like a good'un now though 😃 It also feels like it's been remapped, the increase in power and throttle response is THAT noticeable.

Mike
Click to expand...

Mike have you thought about gutting the cat then welding a pipe between the two opening, (so its like a straight through exhaust pipe) rather than just leaving the Cat shell as an empty box with the exhaust gases going into it. If noise is an issue I suppose you could even add some exhaust silencer wadding around the new pipe inside the gutted cat casing to quieten things down.

Could be your next "line" to add to the list of other products
 
MACK said:
Ducklakeview said:
Nautrey said:
I was just looking into decats. Does anyone know if there is a bolt on kit or is it just a matter of getting one fabricated?
Click to expand...

The way I have done mine is by removing from the car, carefully removing the heatshield and then opening up the cat with the plasma. I then gutted them before welding up and replacing the heatshield. As a result, my car looks standard underneath and no problems with the mot. As mentioned, if the cats are visibly missing, it is a fail.

Mine pops and crackles like a good'un now though 😃 It also feels like it's been remapped, the increase in power and throttle response is THAT noticeable.

Mike
Click to expand...

Mike have you thought about gutting the cat then welding a pipe between the two opening, (so its like a straight through exhaust pipe) rather than just leaving the Cat shell as an empty box with the exhaust gases going into it. If noise is an issue I suppose you could even add some exhaust silencer wadding around the new pipe inside the gutted cat casing to quieten things down.

Could be your next "line" to add to the list of other products
Click to expand...

Nooo... I LOVE the noise it makes now!!

Mike
 
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