Do I need a Catalytic Converter (Cat) to pass an MOT?

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Super Moderator
Original Article Credit: Monkfish



The common answer to this question is "It's an Import, so no". This is incorrect. If you own a Glanza, it will need a Cat to pass the MOT. If you own a GT, it depends on its date of first use (This is found on the V5) although this will only effect the later Mk3 Quadlights.

Ok, so the MOT handbook currently states that any car first used before 01 Nov 1995 where the engine code is not in the DVLA database (ie, the 4E-FTE fitted to all Starlets) only has to pass the basic emissions test. The basic emissions test consists of measuring the exhaust CO2 levels at idle, with the failure limit at 3.5%. If your 4E is over this limit, even without a cat, you either have it fueled to run a turbo the size of a dinner plate or it is fucked. If you garage tells you that your car needs a cat test, tell them to re-read their MOT handbook or go elsewhere to a place that isn't employing morons.

However (this is the bit Glanza and Mk3 GT owners need to pay attention to), if your car was first used on or after 1st Nov 1995 where the engine code cannot be identified, then it needs to pass the basic cat test. This test differs from the basic emissions test in that the CO2 limit is 0.5% at idle and 0.3% at fast idle (Usually around 3,000 rpm). As you can see, it is quite a lot tighter than the basic emissions test. My GT, running 1 bar and with a decat measured 0.86% at idle and was borderline with the cat on. In short, don't smash the guts out of your cat as a cheap de-cat as you'll need it for the MOT.

Note:- On the V5, "Date of Registration" is different to "Approximate date of first use". The first is the date the car was entered into the DVLA system (ie, when it was imported), the date of first use is the approximate date the car was registered in Japan, taken from what little paperwork will be with your car.

This is the flow chart used by MOT stations to determine if a given car requires a Cat test...
mot-cat.gif

(Thanks to kieran.s for digging it up from an old thread)

So there you have it, all you need to know about Cats, MOT's and the little Starlet. If you live in a different country to the UK, you will need to check the rules and regs with your local governing body.
 
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