MOT emissions tests

If it's in the vehicle database as needing a cat test, that's what it should get (However, if the tester knows it had a cat as standard but doesn't now, that's an automatic RFR.). If it's not in the database it gets a non-cat test.

Exemptions are quadricycles and electric/combustion engine (Hybrid) vehicles, Two stroke engines unless they are subject to the catalyst test and any engine with proof from the manufacturer of original limits (some imports or specialised engines).

And yes, a working cat will make quite a difference - that's why you remove it between MOTs

Happy to refit one if it will genuinely make a difference. I'll keep it in mind!

The database of emissions on the MOT emissions tester is from the book - www.gov.uk/government/publications/in-service-exhaust-emission-standards-for-road-vehicles

Note the serial number cut offs.


The Rover Mini has the following listed:

Mini Model Code XN
1.3l Auto TBi Engine Code X Serial No 059845 onwards 0.75 775 975 0.3 200 0.95 1.09 2500 3000 70
1.3l Manual TBi Engine Code X Serial No 059822 onwards 0.75 775 975 0.3 200 0.95 1.09 2500 3000 70
1.3l TBi Engine Code Y Serial No 060488 onwards 0.75 775 975 0.3 200 0.95 1.09 2500 3000 70
1.3l MPi Engine Code Z 0.5 775 975 0.3 200 0.95 1.09 2500 3000 70

The MOT tester should follow closely all the prompts that are given when entering the vehicle details for the emissions test, which should ensure that a non cat test is carried out if the car qualifies for one.

A missing factory fitted cat is not a reason for refusal if the car qualifies for a non cat test.

Maybe your tester is friendly .

What year was the car built?

I've had some right strange ones.

My 1991 Porsche 944 Turbo was meant to have a cat. It basically had a straight bit of exhaust from the Turbo back loosely speaking. Despite being chipped and smelling rich it managed to always pass the emissions.

Technically my '89 S2 should have had one but the very early cars didn't. Again, passed the emissions without a hitch. Even my Stag with a 4 barrel Holley and my MGB with twin SUs passed the test with flying colours and ran fine.

My 1990 MX-5 however with a decat was hopeless. It never got under the 3.5% CO and 1200ppm threshold despite my MGB being able to. I wonder why to this day. The only things I can think of it being were either the CTS being borked but the ECU seemed happy there. The only other thing I can think of is that the ignition timing was too advanced, which was a mod done by many people. That said the emissions on that car did start to suddenly get worse over the years.

If that's the case and your car came with injection as per the DVLA leaflet above you stand no chance*.











*unless you find another way (cough) .

I'd be tempted to call up British Motor Heritage. In the manual it states it is one way to get the figures that you desire. The manual does not mention a carb'd Mini in the list.

But a Cat would bring down the figures. Remember that the Yanks had cats on cars for years long before us. My Carina with a twin choke carb even has a choke on it!

I was asking which cars fall into the exclusion list detailed in the testers guide as I couldn't believe that my Carb car could pass the same test as an injection one, even with a cat. The posts above indicate that it should though.