Hi all,

Am looking at getting a downpipe, this one specifically:
https://www.possumbournemotorsport.c...wnpipe-2.0l-tw
OR the decat version:
https://www.possumbournemotorsport.c...win-scroll-jdm

I understand that a decat exhaust will have a greater power increase and they are also cheaper. BUT will this pass an MOT/emissions test? I have a Invidia R400 catback exhaust which has some filtering along the piping as shown in photo below

My question is - will s decat exhaust fail MOT/emission tests in UK? Even with my existing catback exhaust

 

officially it will fail a UK test both emissions wise as well as the visual check they now do.......

unless your aiming for crazy power then your better off with a proper Sports Cat and suitable map anyhows as they will spool faster and offer more torque than the de-cat

 

Thanks mate, appreciate your replies on all my threads so far!

 

I think hayward and scott showed a 2 bhp difference between a sports cat and a de cat , so power wise there’s nothing in it , a 200 cell sports cat when warm will pass an mot , as above no cat won’t , so is it worth the hassle every year ? I have a good sports cat on one car which works very well power and mot wise , the second car a japspeed one is was not expensive and works fine , people have been buying used prodrive cats or other options are the hayward and scott one which is not cheap but should be good 👍

 

As Stockcar says: Fail. It will fail on CO (carbon monoxide) emissions without a cat.

Technically a sport cat could fail as well if its not a reputable brand, as it may not have the correct (or legitimate- as in verified ) approval markings.

And further more shouldn't even be sold in the uk under law: https://www.legislation.gov.uk/uksi/.../contents/made

But that's out of a MOT's testers remit...so long as it looks like a cat (and it passes emissions) they have no technical resource to verify if it's the correct one for that make/model/year car (bear in mind that legitimate replacement ones are often different shapes/sizes and markings are rarely visible). Make sure the under trays are fitted so visual verification is made more difficult

 

My car is over 500bhp. Have put a 200 cell cobra sports cat on and it required a slight change in the map. It is also not a case of just fitting a cat on for it to pass, it should be mapped correctly afterwards. I run an aftermarket ecu. My exhaust is a 3".Miltek

 

I've got that brand new but shoddy H&S jdm hatch downpipe if you want it for peanuts. I'm not going to lie, it may need tweeking to fit from accounts I've heard from others, but they do produce good power. My spec c was left standing on its oem cat by another hatch equipped with one at Coombe.

 

A decat doesnt give much more power, it may give you a slightly quicker spool, but again not a massive gain.

 

As said go 200 cell, not 100, mine is a pain to get through mot.