Decat & MOT.

-westy-

-westy-

-westy-

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Hi,

I'm going to be replacing the exhaust on my MX5 soon, as my current one is...well, knackered. Chances are that any exhaust I get will be a stainless one, probably with a Decat.

Now, the question I have is, if the car was registered before 1992 (Which AFAIK is the date from which cars had to be fitted with a Cat), but has a cat fitted as standard, does it still require one for the emissions test?

Thanks :)
 
Correct as far as Im aware.

With a decat on a post 1992 car, you have literally no chance of passing, as the CO/Co2 readings go through the roof.

Ive taken readings with and without the CAT, and the readings were at least ten times what it was with the CAT.
 
Dr. Pain said:
Correct as far as Im aware.

With a decat on a post 1992 car, you have literally no chance of passing, as the CO/Co2 readings go through the roof.

Ive taken readings with and without the CAT, and the readings were at least ten times what it was with the CAT.
Click to expand...

I've just stuck a 2004 Impreza WRX with a full stainless steel exhaust and remap through an MOT at a Subaru dealership and it passed no problem!
 
Maz said:
I've just stuck a 2004 Impreza WRX with a full stainless steel exhaust and remap through an MOT at a Subaru dealership and it passed no problem!
Click to expand...

It will fail after January though, assuming the new regs come in.
 
Maz said:
I've just stuck a 2004 Impreza WRX with a full stainless steel exhaust and remap through an MOT at a Subaru dealership and it passed no problem!
Click to expand...

Yeah but did it really "pass" or did they use another car?!

There are so many friendly MOT stations these days!

Guess it must depend on the engine, but why bother with a CAT from the factory then if the emissions are fine without? Just the law, regardless of how clean the engine is without a CAT ?
 
What are the new regs?

Let me guess. The car must be fitted with a cat if it came with one from the factory? Regardless of the emission levels.
 
Dr. Pain said:
Correct as far as Im aware.

With a decat on a post 1992 car, you have literally no chance of passing, as the CO/Co2 readings go through the roof.

Ive taken readings with and without the CAT, and the readings were at least ten times what it was with the CAT.
Click to expand...


c02 isn't even tested on the MOT.

You'll find c02 levels increase dramatically with the fitment of a catalytic converter.
 
Dr. Pain said:
Yeah but did it really "pass" or did they use another car?!

There are so many friendly MOT stations these days!

Guess it must depend on the engine, but why bother with a CAT from the factory then if the emissions are fine without? Just the law, regardless of how clean the engine is without a CAT ?
Click to expand...

The car did actually pass an emissions test with the de cat, it would have passed regardless as the tester is a friend - but it did genuinely pass without the need for manipulating the results.

Car had been out for a good 15-20 min blast first though.
 
Dr. Pain said:
Correct as far as Im aware.

With a decat on a post 1992 car, you have literally no chance of passing, as the CO/Co2 readings go through the roof.

Ive taken readings with and without the CAT, and the readings were at least ten times what it was with the CAT.
Click to expand...

Loads of people on the Integra DC2 forum say they pass emissions no problem with a decat
 
Maz said:
The car did actually pass an emissions test with the de cat, it would have passed regardless as the tester is a friend - but it did genuinely pass without the need for manipulating the results.

Car had been out for a good 15-20 min blast first though.
Click to expand...

Having a big blast prior to an MOT is simply to heat the CAT up to temperature so it works optimally, wouldn't make a blind bit of difference if the CAT isn't there.
 
Dr. Pain said:
Yeah but did it really "pass" or did they use another car?!

There are so many friendly MOT stations these days!

Guess it must depend on the engine, but why bother with a CAT from the factory then if the emissions are fine without? Just the law, regardless of how clean the engine is without a CAT ?
Click to expand...

Loads of cars really pass the emissions test without their cat (it's cat not CAT by the way - it isn't an acronym) but as of 2012 MOT regs will dictate that if it left the factory with one, it has to have one.
 
Maz said:
The car did actually pass an emissions test with the de cat, it would have passed regardless as the tester is a friend - but it did genuinely pass without the need for manipulating the results.

Car had been out for a good 15-20 min blast first though.
Click to expand...
Short of leaving the probe hanging out of the exhaust so it doesn't get an accurate reading, or testing an entirely different vehicle, you cannot really manipulate the results, it isn't possible to manually change them or anything like that.
 
The law as it stands is,

Post 1992 UK car will need a cat or very efficient engine to pass.

A car which is not on the system i.e. an import has until mid 1995.

There is a flow chart all MOT stations will have and as long as they test it as a Eunos Roadster or Nissan Pajero etc etc, it will fall under the pre 1992 rules.

YES, YES, YES, NO.

emissions.gif
 
Somehow, some cars pass MOT emissions without cats. A friend of mine's Subaru which is fully decatted and remapped passes every time! And that's without a friendly MOT tester..
 
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