Hi all,
Here is a tip for passing the MOT smoke test. You may already know about it - but here goes.
My original smoke reading was 6.85. The pass level is 3.7 for turbo deisels. The tester suggested I run the car around the bypass in second gear (O/D off), keeping the revs around 500 below the red line.
The result was a reading of 1.6.
So the conclusion is - dont spare the horses on the way to the test station! - Cheers
- (#6587) Mark Wolff, 20 Dec 02
Maybe I'm quite fortunate but with regard to the smoke test, my mot station has a policy of "If we can still see the garage doors, it's passed". Even more fortunate (touching tree type substance) is mine's pretty good anyway
- (#6588) Dave B, 20 Dec 02
Well, Dave, it sounds like your MOT is invalid then...
- (#6589) david miller, 21 Dec 02
hi everyone i'm a pride owner of a 92 liteace which i've had for a year now (which i'm well impressed with having two young children and a big german sheperd, i could'nt have asked for a better car) but the problem is that i took it for a MOT it passed everything but the emissions(which was 8.16) when i got it home i put vavle/diesel cleaner it and took it for a good run and then i turned the 'smoke screw' half a turn clockwise(i know most of you said not to do)thinking clockwise was the right way i.e closing and then took it back down to be MOTed but again it failed on emissions (again being 8.16)so i tryed turning the max. fuel screw first i tryed clockwise but it would'nt turn looking closer i noticed their was a plate wielded to the thread so i could'nt move it in so i unscrewed it anti-clockwise which worked and in turn bought the revs down IS THIS RIGHT WHAT I HAVE DOWN? p.s forgot to say blocked of airpipe from top of pump to inlet manifold when i first done the smoke screw which i got to say it improved the proformance
- (#6930) ian thomas, 25 Jan 03
anticlockwise to reduce fuelling...- you'll hear the idle speed decrease if you go the right way.
Oh, and if you've blocked the boost sensing pipe, the adjustment won't do as much. That shouldnt've improved the performance tho. Perhaps you have other issues? Has the timing been adjusted?
- (#6931) david miller, 26 Jan 03
thanks for getting back to me sorry for the delay I removed the block from the boost sensing pipe (1 because you said and 2 the turbo light stopped working i think the turbo was still working though)i turned the max. feul screw like you said the revs came down to about 850 ish and when hot rose to just under 1000 took it to MOT station but still failed (first test was 8.16 the second was 7.27 average {lowest was 6.17})so i went to a local diesel specialist and he said he,ll remove injectors and test them and also said that (can't remmeber exactly)over fueling pipe was putting dirty fuel back into system i think he said it'll take about 2 hours at about £85ish and he said he could service the injectors for about £20 i think? does this sound right? or is it cheaper to get new ones (if so do you know part No and price)and 1 more thing he said that i can't adjust the pump to lower the emissions?i did a little bit. just one more thing i think this site is just brillant i've found out so much about my liteace i just wish i had a computer before i bought it
- (#7008) Ian thomas, 1 Feb 03
sorry didn't answer your last question the timing hasn't been adjusted since i've had it
- (#7009) Ian thomas, 1 Feb 03
I had a similar problem with emmisions when i took my townie for test,got readings about 5 or 6 even after blasting up and down the bypass in second gear and putting injector cleaner in tank - the mechanic at the garage made an adjustment for me on the back of the injection pump,there is a screw in the middle in between the fuel pipes,he turned it a quarter turn anti-clockwise and instantly my reading dropped to 1.6 - dont know what he adjusted but it did the trick.
- (#7010) pete, 2 Feb 03
Pete,
I had very similar readings and, the local diesel specialists did the same adjustment for me. With all the advice available on this site, I was intending to make the adjustment myself but, the diesel specialist has the testing equipment to verify the emission reading and I did not want to risk failing the MOT test on a "hit or miss" adjustment. However, with a "pass" reading similar to yours, the performance of the vehicle was very much reduced. Did you have this result? I have had to adjust my pump back to obtain an acceptable performance figure but, I fear that it will not pass an MOT test now or, any of those roadside emission checks which are to be introduced locally during this month. I would appreciate any comments which others might like to make re the "trade off" between performance and getting the vehicle through the emissions part of the MOT
- (#7011) John Davis, 2 Feb 03
Have any 0f you pump-tweakers checked your fuel economy after adjusting for black smoke? I note the lowering of performance, but is there a corresponding gain in MPG? I would happily give up a little of the power for a reasonable reduction in my fuel bills!
- (#7012) Tom Lister, 2 Feb 03
minimal. smoke comes in heavily as soon as you exceed the amount of fuel that can be burn in the available air. That's what makes it such a fine adjustment. In theory anyway, you shouldn'd lose any power going from mot- fail smoke to mot-pass smoke...
- (#7013) david miller, 3 Feb 03
Thanks David. I had reasoned that the excess fuelling, though considerabling increasing the emissions figure, was not contributing much to the power output and, possibly, the diesel specialist reduced the fuel rate to be on the safe side for the MOT. I think it's time to make a few very small adjustments and experiment a little.
- (#7014) John Davis, 3 Feb 03
I have been making the same adjustments to my pump with Davids help.
I have been tweeking now for about 2 weeks.
Went from Somerset to East Sussex return Sunday 440 miles cost approx £50. M5 M4 M25 70 mph and head wind on the way home. Still smoking a bit on hills when I put foot down more. Also I forgot to connect kick-down cable back up last week. Still about 30 mpg.
I have turned anti-clockwise to back of a touch today, now hardly any smoke only when I rev up or start motor. Power seems to be still ok. Will let you know.
Phil
- (#7053) phil cook, 4 Feb 03
Mr Miller, you would be quite right in your statement about a dodgy mot but I've only had it about 6 months so I've not mot'd it yet. My mate (the garage mechanic) is a bit of a joker and I didn't think his comment would be taken so literally. He does say however that they need to smoking quite badly before they are bad enough to fail.
- (#7183) Dave B, 11 Feb 03