High Emissions
Turbo Mini Forums

My car failed its MOT today on the emissions

CO% 8.8 should have been <3.5
HC ppm 9692 should have been <1200
O2% 7.71 should have been <2.5

I suspect that the car is running a bit rich but the MOT guy said that the numbers were ridiculously high.

Whats the best way to get the emissions down?

try to recalibrate the carb firstly

but.... these MOT monkeys are solid in the head!

pull the vacume pipe of the dizzy & adjust the tickover to suite

limp the car in then let this monkey check the emissions

it will fly through!

then you have you ticket !

you can set the mixture at a more friendley garage soon after ! hese angling for some coin off you!

these MOT monkeys are full of crap they are a law unto them selves, i hate the lot of them!

not for the wrong reasons as saftey is everthing but most of them are as thick!!!!! as a table top!

rant over

I had a simmilar problem earlier this year. in fact every year. I can make it run very lean, but this can actually increase the HC reading. After the first fail, I slightly increased the mixture (using lambda reading) to as close to correct as possible, then I advanced the ignition. It was guesswork and it just scraped through.

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Mines been close for the last two MOT's. My MOT man is friendly and actually allowed me to test my car on his spare gas analyser so i played about until i got it right.
As Will says leaning the mixture off to much will bring the HC up, as will going to rich. You need to find a happy medium. I also swung the dizzy and found a happy medium for this. One other thing i did was cover the radiator so the engine was nice and hot, this helped somewhat.
Yours does sound way out so i would suggest a good tune up.

Phil.

WWW.TURBO-MINI.COM

Mine passes easily enough, and its running Phase 2 cam with 1.5 rockers.(Not that it needs to be tested cos mines a 1968 car!)

If you can't tweek the mixture screw, then it might be a good excuse for a carb re-build and a rolling session. (A worn needle valve will leak at idle and make it run rich)

never knew that, any idea what sort of rev range it has to be taken in?

I believe the guide in the MOT testers manual is 2500rpm or thereabouts.

Cheers for the replies guy's.

I'll turn the mixture down and take it back to him.

Is it correct then that if it doesn't pass at idle rpm, he should retest it at 2500.

As soon as i can get it roadworthy it'll be going to a rolling road to be setup properly.

Thanks again

if you vac advance disconect it and block off at the carb this made a lot of difference to mine on the hc front.

high hc is also linked to overlap on the cam is your cam lumpy on tick over.

always looking for them bigger bunches of bannanas

Yeh, pretty lumpy. Its a 286.

say no more then, but it still shouldnt be that high.

a 286 will read about 2000 to 2500hc disconect advance and back ignition off this may help.

always looking for them bigger bunches of bannanas

Hi,
Unless the regs have changed, it used to go like this (I was a MOT tester, thanks Benross!) If the car passed on CO but failed on HC the revs should be raised to 1200 (I think) RPM to see if the HC then passed.
This was nearly always the case on MG Met-rots. Most common cause is a worn needle and jet. Because it's spring loaded, the needle is pushed up against the side of the jet when air is going through the carb, this wears a visible flat edge on the side on the needle.
Now your fuelling is all fucked up! I should imagine this wear is accelerated by the turbo! HTH
Cheers,
Gavin. :)
PS The ministry of transport are actively recruiting monkeys who know nothing about cars, because they want it tested as per the manual, not the testers "judgement"

Edited by Bat on 4th Dec, 2005.

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no offence Bat, i bet you were one of the good ones


bat said.
PS The ministry of transport are actively recruiting monkeys who know nothing about cars, because they want it tested as per the manual, not the testers "judgement"

HOW TRUE!

Hi,
@ Benross, none taken mate. I'll tell you something though, I'm glad I don't have to deal with them idiots anymore... You pass it and they complain, you fail it and they complain! I got fed up with it in the end!
Cheers,
Gavin. :)

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