MOTs and CATs

[JSG]

Got this from another forum where someone was trying to clarify the LPG issue, but it has relwvance for all cars. This explains why some people have not had problems getting MOTs without cats fitted.

Cheers,
JSG

quote:
'This is the reply to my email to the Department of Transport on the matter.

Dear David

Thank you for E mailing the Department for Transport

'The MoT test requires most petrol fuelled passenger cars first registered after 1 August 1992 to pass low and fast idle emissions tests measuring carbon monoxide, hydrocarbon and lambda (air fuel ratio
relative to the ideal). Vehicles presented for test running on LPG are however only subject to a low idle check on carbon monoxide and hydrocarbon emissions.

There is no requirement in the MoT test that a catalytic Converter be fitted, however section 7 of Regulation 61 of the Road Vehicles (Construction & Use) Regulations make it an offence to modify a vehicle in such a way as to increase its emissions relative to the level which the vehicle met when new. Removal of a catalytic converter would significantly increase emissions, even on vehicles running on
alternative fuels such as LPG, and would therefore be an offence.

The MoT test is merely intended as a rough test to detect major failures in emissions control systems, it is not sufficiently sensitive to 'certify' low emission vehicles. It is possible that some vehicles
might pass the MoT test, but still emit significantly higher levels of pollutants than they were designed to when driven on the road.'

[Basil Brush]

So, subject to passing the emmission requirements, fitting a straight through box which looked like a cat would allow decatting without the grief of refitting come MOT time as they wouldn't know the difference? Or alternatively am I clueless and it's not that simple?

[JSG]

What it means is that whilst its illegal to remove your cats (if it makes your vehicle more noxious) MOT stations don't have a requirement to check they are present.

Cheers,
JSG.

[JohnL]

So yes you could remove the cat and still pass the MOT, provided it still met the "new post 1992" emissions standard.

But it would still be illegal unless somehow it managed to meet the same emissions levels without the cat as it did with it. Although I can't see anyone ever checking that, since it's not an MOT requirement (which is odd come to think of it).

[ianwayne]

Since part of the test on cars registered after 1/1/93 is that the CO level is less than 0.5%, I fail to see how ANY car could pass this without a cat! If memory serves me well, the last non-cat car I had produced about 3% CO (2 litre Cavalier GLi).
The max. level allowed increases to 3.5% for vehicles registered 1/86 to 1/93 and up to 4.5% before Jan '86. I think for those before 1973, as long as its not too smoky, its OK!
The reason I think it is possible to pass with TVR manifolds decatted is that there is one in the Y piece doing sufficient work to get the level down. At last MoT, mine was 0.009% so maybe a 'little' decatting would be OK??