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Thread: Emissions check

  1. #1
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    Nov 2006
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    Default Emissions check

    I asked my local dealer to give me a reading of my car's actual emissions (it's 2 years old) and to compare it with what the manufacturer says it should be and what the MOT test requires for a pass.

    Firstly, they admitted that their testing machine is not really up to the job. (This is a Volvo main dealer......)

    Second, they took the car to an MOT testing station and got the printout, which was a PASS as expected.

    Thirdly, no-one understands the details printed on it, so I still don't have my question answered!

    So, the conclusion is that whilst I would like to know how good or bad the emissions of my car actually are compared to the statistics for it and the law, no-one knows how to work it out anyway. Therefore, emissions testing is clearly too complex and that what the manufacturers quote for new cars has nothing to do with what your car actually produces. AND they base your tax on these figures!!

  2. #2
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    Hi

    Firstly manufacturers quote in Carbon Dixode terms ie CO2 Combined emissions (g/km) 265.The emissions tester that any garage uses will display Carbon Monoxide (CO) Hydrocarbons (HC) Lambda and Oxygen (O2).

    So as you see the data the manufacturer provides for taxation is different to the parameters that are measured on a garage based emissions test.This link may help http://www.greenconsumerguide.com/transport_main.php

    If your vehicle met the criteria for an mot test pass then you have nothing to worry about as that is the whole idea of the test i.e to ensure vehicles meet a stringent limit of emission figures and are not running ineffieciently and polluting the atmosphere.The only figures you can use to compare would be the technical data for your vehicle so you see what the limit is for CO/HC/Lambda and O2.This will tell you if your car is running as it should be.

    If you need explaining what the figures are on your results post them and I will decipher them for you.

    HTH
    Last edited by Sussex Patrol; 04-03-08 at 22:01.

  3. #3
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    can you tell me what these mean completly baffled

    [IMG]http://i29.photobucket.com/albums/c286/bobdawkins/DieselSmokeTest001.***[/IMG]

  4. #4
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    Hi

    Ahh did'nt realise your vehicle was a diesel! The parameters I posted were relevant to a petrol engine test. Yours being a diesel is subject to a diesel emissions test which is done in a different way.The diesel smoke tester is measuring the density of the emissions (which is expressed in m-1).

    The 'm' is for molar volume see this link http://en.wikipedia.org/wiki/Molar_volume

    The vehicle is revved up to max of six 'free accelerations' to get the average(mean) reading of the last three readings.I belive the current limits are as follows non-turbocharged engines no more than 2.50m-1 and for turbocharged engines no more than 3.00m-1.

    Looking at the scan above the emissions have failed the test as the average is 8.91m-1 There could be many reasons it may just need 'an itailan tune up' to clean the exhaust or could blocked air filter/fuel filter or faulty injectors or injector pump. Your need to establish why the emissions are high.

    This is copied from the Haynes website :

    The only emission test applicable to Diesel engines is the measuring of exhaust smoke density. The test involves accelerating the engine several times to its maximum unloaded speed. Note: it is of the utmost importance that the engine timing belt is in good condition before the test is carried out.
    The limits for Diesel engine exhaust smoke, introduced in September 1995 are:
    Vehicles first used before 1st August 1979: Exempt from metered smoke testing, but must not emit "dense blue or clearly visible black smoke for a period of more than 5 seconds at idle" or "dense blue or clearly visible black smoke during acceleration which would obscure the view of other road users".
    Non-turbocharged vehicles first used after 1st August 1979: 2.5m-1
    Turbocharged vehicles first used after 1st August 1979: 3.0m-1

    Excessive smoke can be caused by a dirty air cleaner element. Otherwise, professional advice may be needed to find the cause.

    original link http://www.haynes.co.uk/webapp/wcs/s...atalogId=10001

    HTH
    Last edited by Sussex Patrol; 04-03-08 at 22:02. Reason: added extra info

  5. #5
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    Hi SussexPatrol and BobDawkins. Thanks for all the information you're bringing to this debate. To my mind, it is showing how difficult it is for the average motorist to understand emissions and yet we're all supposed to know how to reduce them! The MOT test gives a PASS or FAIL as demonstrated above, with a patronising pat on the head that says don't worry about HOW we got the result, just accept that you've either passed or failed the test. Oh - and if it fails you've got two weeks to fix the problem that we can't possibly tell you what it is.

    My original question still stands. How do I compare the Manufacturer's stated emissions data for the model against what my car actual produces and against what the MOT says it should not exceed?

    Can anyone answer this please? It's beginning to seem like a can of worms.

  6. #6
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    Yes, tuning didn't solve the problem, my mate the mechanic hopefully solved the problem by putting on another fuel pump, noticed soon as he started car, no black smoke even when revving it to MOT standards, Black smoke 0, Fuel pump 1, while he was at it he changed turbo, [slight wear in bearing], and done head change as well, not him, the car, [ bit noisy, like when its cold, but sounded like it all the time], so he is taking it for MOT in the next couple of days, will let you know how he gets on Bob

  7. #7

    Default

    With a diesel, the things to look at are:

    Fuel Filter
    Air Filter
    Injectors
    Fuel Pump Adjustment

  8. #8
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    All checked, replaced, or changed,

  9. #9
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    @ Andy H

    We need to break this down.Firstly the figures quoted for taxation are quoted in CO2 (carbon dixode).This is how manufacturers let the Government know how much there vehicles pollute the atmosphere. The Mot emissions test does not use this criteria.

    The Mot emissions test will depend on the type of fuel used ie petrol or diesel so in the case of a diesel see my previous post.In the case of a petrol engine depending on what year the vehicle was manufactured will influence what criteria is used but in the main if the vehicle is manufactured before 1993 then the CO (carbon monoxide) and HC (hydrocarbons) are measured and for a cat eqiupped vehicle it is subjected to cat test this will measure CO/HC and lambda readings.

    All you need to worry about is that your vehicle passes these requirements.The manufacturer will also have figures in their technical data ( not to be confused with the taxation data).

    In regards to keeping emissions down as motorists we can do this by using good quality fuels and making sure the vehicle is serviced in accordance with the laid down schedule ie time or mileage.

    If your vehicle fails the test it is not the job of the mot test to diagnose failure as the mot is just that a series of visual checks that determines if your vehicle meets a required standard at the time of test to be considered safe to be on the road.

    As you can see from previous posts if a vehicle fails the emissons test there can be many reasons for the failure which mean diagnosis can take time.

    The taxation figure will not correspond to the figures used for the MOT test.

    HTH
    Last edited by Sussex Patrol; 04-03-08 at 22:02.

  10. #10
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    Sep 2007
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    Default Comparing actual emissions to Manufacturer's published g/km

    Hi,
    I own a BMW 760i (2003) with a 5792cc v12 engine and a manufacturer's CO2rating of 330g/km. It is a really beautiful car and I don't want to give it up, but I feel quite strongly too that I should do something about reducing my motoring carbon footprint.
    I have calulated my precise carbon output for the last year and set a target of 35% reduction for the forthcoming year.
    Much of that reduction will be achieved by restricting my use of the car and using bus/train for journeys where feasible - even walking sometimes!
    However, I also plan to carry out some experiments using various types of emissions reducing technology (magnetic induction, lpg/dual-fuel, etc) and I am prepared to spend some money on it.
    My question has been asked already, but I cannot see that it has really been answered yet ............. How is the manufacturer's official grams/kilometre figure derived? - the figure used by the DVLA to fix licencing levels - and how can it be re-tested from time-to-time as I make changes to the car.
    So far as I can see, the only real way of determining whether or not a car is actually becoming genuinely less pollutant is to run a continuing series of tests - first establishing a consistent base level - before making a change to the car and running further series of tests after each change - and so on ....
    It seems from previous discussion on this forum that, at the moment, all that is available to the motorist in terms of an indicator of how much he/she is polluting the atmosphere is an initial manufacturer's rating, followed annually by a "pass/fail" decision from an MOT test station. It would seem that the MOT test simply does not output actual values of any of the gases (CO2, CO, NOx etc.)
    Does anyone know how I would go about getting a full gas analysis carried -out frequently, or on an "as required" basis. Can you buy your own equipment? Are the criteria for the test set by the DVLA?
    I hope that someone can help.
    Thank you
    BJM

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