Does a diesel need a CAT to pass an MOT?

PAz · 14 Oct 2007 at 19:13

Hi

As title really, I've read that a diesel doesn't need a cat to pass an MOT...can anybody confirm this is true? Some googling suggests yes but just want to clarify

Can't decide whether to go for a full system with decat or just a straight through after the cat...

Ta

Muncher · 14 Oct 2007 at 19:31

PAz said:
Hi

As title really, I've read that a diesel doesn't need a cat to pass an MOT...can anybody confirm this is true? Some googling suggests yes but just want to clarify

Can't decide whether to go for a full system with decat or just a straight through after the cat...

Ta

Doesn't need one. My 1995 diesel Golf certainly went through without one, CO2 wasn't even tested.

Stonedofmoo · 14 Oct 2007 at 19:36

No it doesn't need one, and it's not a CAT, its a particle filter

As long as the smoke levels don't exceed the test spec it will pass, nothing else is tested on a diesel.

L0rdMike · 14 Oct 2007 at 19:42

So it can put out as much crap as it likes as long as its not smokey?

Stonedofmoo · 14 Oct 2007 at 19:43

L0rdMike said:
So it can put out as much crap as it likes as long as its not smokey?

Basically, yes. With diesels the smoke IS the ***p

L0rdMike · 14 Oct 2007 at 19:44

How is the test done by eye or is a device used?

PAz · 14 Oct 2007 at 19:45

Cool, might go for the full system then

Thanks guys

Stonedofmoo · 14 Oct 2007 at 19:50

L0rdMike said:
How is the test done by eye or is a device used?

A device is used, I don't know the technical details but I've seen the pass slips.

Lopéz · 14 Oct 2007 at 19:57

L0rdMike said:
How is the test done by eye or is a device used?

Device.

pinkaardvark · 14 Oct 2007 at 21:19

Lopéz said:
Device.

Does it involve a hamster and duct tape? or was my mate down the pub just taking the pish?

Butters · 14 Oct 2007 at 21:30

Stonedofmoo said:
No it doesn't need one, and it's not a CAT, its a particle filter

As long as the smoke levels don't exceed the test spec it will pass, nothing else is tested on a diesel.

No, its a CAT. Diesels have CATs and particle filters

Stonedofmoo · 15 Oct 2007 at 08:37

Butters said:
No, its a CAT. Diesels have CATs and particle filters

I see, on Peugeots 306 its a particle filter only. They must be cracking down further on more modern cars.

BigglesPiP · 15 Oct 2007 at 15:58

Depends on the car, the condition of the car, and the age of the car.

blueboy2001 · 15 Oct 2007 at 17:11

Most modern diesels will have a Cat as they reduce NOx emissions. Some very modern diesels have particle filters which trap and burn off particles but these will do nothing to reduce NOx.

A Peugeot 306 HDi will have a cat, it certainly won't have a particle filter - the first car fitted with a particle filter was the PSA 2.2 HDi engine fitted to the 406 and the C5.

Diesels require a cat to meet emissions regualtions, but this is not (currently) tested during an MOT. Diesels are subject to a smoke opacity test which only measures the opacity of the smoke coming from the exhaust.