what is a decat?

panthro · 26 Sep 2007 at 10:04

begbo said:
Mite be wrong here, but if a car has a turbo has it not got more chance of passing an mont without a decat compared to a N/A without one. As turbos give out less emissions?

What? My impreza gives off something ridiculously high like 280g/km.

jpmonkey69 · 26 Sep 2007 at 11:02

BigglesPiP said:
Illegal for use on the road.

It seems you need to research your opinions before you go off saying that they're fact.

Dogbreath · 26 Sep 2007 at 11:20

jpmonkey69 said:
It seems you need to research your opinions before you go off saying that they're fact.

If the de-cat pipe raises emissions above the relevant levels for the vehicle as stated in the Motor Vehicles(Construction and Use) regulations, then it is an offence to drive it on the road. However, the mere absence of a catalytic converter is not in itself an offence AFAIK.

jpmonkey69 · 26 Sep 2007 at 11:23

Dogbreath said:
If the de-cat pipe raises emissions above the relevant levels for the vehicle as stated in the Motor Vehicles(Construction and Use) regulations, then it is an offence to drive it on the road. However, the mere absence of a catalytic converter is not in itself an offence AFAIK.

I know that, but the Biggles said that a decat was illegal on the road, without any qualifier.

It's not the first opinion he's stated as a fact which is wrong.

Jonnycoupe · 26 Sep 2007 at 11:29

panthro said:
What? My impreza gives off something ridiculously high like 280g/km.

CO2 emission aren't really emissions TBH. Nice to see the media circus works.

Gaijin · 26 Sep 2007 at 11:50

nokinidea said:
then they give you a seven day fix it !!
Not rocket science.

If you are lucky. If they wish, they can declare your car unfit for the road and prevent you from driving it. You'd have to walk home or get a lift and they'd serve you a rectification notice.

ConfusedTA said:
Of course, if you are pulled over by the DVLA/VOSA, and they decide to do a full emissions test there and then, you could fail!

But, you could also fail if you do have a cat in place, if it's degraded or has fallen apart!

The act of fitting a decat pipe in itself is not illegal - but you will have to bear in mind that if you do get pulled over for a spot-check, you could fail the emissions test.

In that case, you just need to know where the VOSA checkpoints could be and make sure you are not in the nearside lane or avoid that route altogether!

panthro said:
What? My impreza gives off something ridiculously high like 280g/km.

I might be wrong but the way your car breathes has little to do with its emissions. How efficient the engine is at combusting the fuel over a given time with differing load levels and AFR's, however, is. I always thought Cat's served to greater reduce emissions from inefficient combustion.

Simon · 26 Sep 2007 at 12:49

Cats will increase C02 emissions. They convert HC and CO into H20(water) and CO2.

The main effect of decatting a car is the smell as unburnt HCs exit the exhaust.

Lopéz · 26 Sep 2007 at 19:33

jpmonkey69 said:
I know that, but the Biggles said that a decat was illegal on the road, without any qualifier.

It's not the first opinion he's stated as a fact which is wrong.

He also stated in another recent thread that cars record how long you have driven without the cat and the police fine you per mile - which sounds distinctly on the outer edge of the believable to me.

My Supra has passed at least 4 MOT's without a cat. My Sierra also passed without a cat. You do not necessarily need a cat to pass the cat test.

Fuzz · 26 Sep 2007 at 19:44

Lopéz said:
He also stated in another recent thread that cars record how long you have driven without the cat and the police fine you per mile - which sounds distinctly on the outer edge of the believable to me.

I lol'd... out loud too.

Fuzz · 26 Sep 2007 at 19:47

Meridian said:
I have a 100-cell in the downpipe myself. But my understanding of using a cat in the cat-pipe (on newages) or centre section is that it doesn't work as effectively, so seriously tuned cars could still fail an emissions test? Not a problem on cars with normal power though.

M

Only if you don't get it hot enough.. being further from the turbo it does take a little more energy to get it burning in it's zone..
A good thrash prior to the MOT is all that is usually required.

Group N cars have them in the tail pipe !!
Any closer to the turbo and they'd overheat and melt because of the Antilag.

Westyfield2 · 26 Sep 2007 at 19:52

Hunders said:
I thought that all cars registered 93> HAS to have a cat in order to pass the MOT?

As others have said in the thread, not having a cat doesn't necessarily mean failing MOT emissions tests.

Also, our Westfield is a Kit-Car built from all new parts so is on the year registration plate of when it was registered (2002 - 52), and has never been tested for emissions at MOT time (been tested for visible smoke only, but was tested for emissions at SVA) - so that's got massively illegal emissions (proper racing manifold and silencer on a race built blueprinted etc engine) but has always passed the MOT!

We have a rubbish silencer with cat in it incase its ever needed (was used for SVA), and a special "Low emissions map" for the ECU also incase ever needed. (But that silencer is very restrictive and gets something like 107db at 4500rpm whereas the cat-free silencer is far less restrictive and gets 95db at 4500rpm.)