Your browser isn't supported
It looks like you're using an old web browser. To get the most out of the site and to ensure guides display correctly, we suggest upgrading your browser now. Download the latest:

Welcome to the MSE Forums

We're home to a fantastic community of MoneySavers but anyone can post. Please exercise caution & report spam, illegal, offensive or libellous posts/messages: click "report" or email forumteam@. Skimlinks & other affiliated links are turned on

Search
  • FIRST POST
    • Craig1981
    • By Craig1981 11th Oct 18, 4:02 PM
    • 560Posts
    • 276Thanks
    Craig1981
    New MOT Diesel Emissions
    • #1
    • 11th Oct 18, 4:02 PM
    New MOT Diesel Emissions 11th Oct 18 at 4:02 PM
    Hi all


    trying to find out some info online, but all stems to the "new" rules for MOT only, and trying to find some first hand experience regarding the new emissions rules under the new MOT


    I have a 2012 2L diesel, it has a DPF, and the items I have found online suggest cars like mine will struggle passing the new MOT.


    just wondering if anyone has had MOT done on a newer diesel car with DPF since the changes come into force?


    many thanks
Page 2
    • sevenhills
    • By sevenhills 12th Oct 18, 7:43 PM
    • 1,836 Posts
    • 703 Thanks
    sevenhills
    Umm, no.

    AdBlue - urea - is used in a catalytic reaction to convert NOx emissions into nitrogen, water vapour and CO2. It's nothing to do with particulates.
    Originally posted by AdrianC

    To put it another way, Adblue is sprayed as a fine mist into the exhaust gases and makes the harmful diesel emissions heavier than air stopping them floating around when emmitted out of the exhaust pipe.

    • motorguy
    • By motorguy 12th Oct 18, 8:21 PM
    • 17,989 Posts
    • 11,015 Thanks
    motorguy
    It's a fail if they spot the DPF is gone though as it's illegal to drive a diesel that should have a DPF without one. Depends how well hidden away it is in the car
    Originally posted by Nasqueron
    Uh huh. However that wasnt my point - we were talking about the smoke test.

    And anyone with half a brain wont have removed the DPF (box), they've have taken it off, cut it open on the top, gutted it, welded it back up and refitted it. Then code out the DPF errors from the ECU.

    Practically undetectable.
    Last edited by motorguy; 12-10-2018 at 8:24 PM.
    "We have normality. I repeat, we have normality. Anything you still can't cope with is therefore your own problem."
    • motorguy
    • By motorguy 12th Oct 18, 8:26 PM
    • 17,989 Posts
    • 11,015 Thanks
    motorguy
    If it's a pre-July 08 car, then easily. But after that... Much harder. It almost certainly won't hit the manufacturer's opacity limit, and would struggle to hit the levels of opacity for a generic post-08 test, though, and especially the post-Jan 14 level.


    And it should definitely fail on a missing DPF, unless it's been gutted in such a way as to be invisible when fitted.
    Originally posted by AdrianC
    Harder but not that hard.

    And likewise pretty much everybody who "removes" a DPF does it in a way that leaves the DPF box intact and present.
    "We have normality. I repeat, we have normality. Anything you still can't cope with is therefore your own problem."
    • AdrianC
    • By AdrianC 13th Oct 18, 9:15 AM
    • 19,709 Posts
    • 18,280 Thanks
    AdrianC
    To put it another way, Adblue is sprayed as a fine mist into the exhaust gases and makes the harmful diesel emissions heavier than air stopping them floating around when emmitted out of the exhaust pipe.
    Originally posted by sevenhills
    You can "put it that way", but you're quite simply dead wrong. That's absolutely not what happens.

    AdBlue is a 32.5% solution of urea, (NH2)2CO. When it is injected into the hot exhaust gas stream, the water evaporates and the urea thermally decomposes to form ammonia and isocyanic acid:

    (NH2)2CO → NH3 + HNCO

    The isocyanic acid hydrolyses to carbon dioxide and ammonia:
    HNCO + H2O → CO2 + NH3

    Overall, this is
    (NH2)2CO + H2O → 2 NH3 + CO2

    From this point, ammonia, in the presence of oxygen and a catalyst, will reduce nitrogen oxides:
    4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O and
    6 NO2 + 8 NH3 → 7 N2 + 12 H2O

    The overall reduction of NOx by urea is:

    2 (NH2)2CO + 4 NO + O2 → 4 N2 + 4 H2O + 2 CO2 and
    4 (NH2)2CO + 6 NO2 → 5 N2 + 8 H2O + 4 CO2

    So what went into that reaction is AdBlue and NOx. What comes out is Nitrogen (78% of the air around us), water and CO2.

    The chemistry's all cut'n'paste from Wikipedia, yes, I don't pretend to understand it all in detail (I got my O-level Chemistry second time round, just). But it's a damn sight more complex and effective than "it gets sprayed which makes it heavier"... Even ignoring the fact that AdBlue and SCR is not aimed at reducing the particulates, which have already been trapped and burnt in the DPF.
    • AdrianC
    • By AdrianC 13th Oct 18, 9:16 AM
    • 19,709 Posts
    • 18,280 Thanks
    AdrianC
    And likewise pretty much everybody who "removes" a DPF does it in a way that leaves the DPF box intact and present.
    Originally posted by motorguy
    Now. But they've simply been putting a bit of straight pipe in for years.
    • motorguy
    • By motorguy 13th Oct 18, 10:54 AM
    • 17,989 Posts
    • 11,015 Thanks
    motorguy
    Now. But they've simply been putting a bit of straight pipe in for years.
    Originally posted by AdrianC
    I have been seeing it done for 5+ years. I've never seen anyone put a bit of pipe in, which would be plain daft from day 1.
    "We have normality. I repeat, we have normality. Anything you still can't cope with is therefore your own problem."
    • Thomas Crown
    • By Thomas Crown 13th Oct 18, 11:15 PM
    • 665 Posts
    • 160 Thanks
    Thomas Crown
    [QUOTE=Apodemus;74905858 Not sure what revs they take it up to on the test [/QUOTE]

    As far as I'm aware, they rev the engine up to maximum ie. until the cut out operates, 3 times. I think that this is horrendous. They treat the engine in my car, in a way that I would never do.
    • Richard53
    • By Richard53 13th Oct 18, 11:31 PM
    • 2,816 Posts
    • 2,334 Thanks
    Richard53
    As far as I'm aware, they rev the engine up to maximum ie. until the cut out operates, 3 times. I think that this is horrendous. They treat the engine in my car, in a way that I would never do.
    Originally posted by Thomas Crown
    It's about fitness. I never treat my engines like that either, but I still believe that an engine should be able to be run at max without failing. If it won't, there is something amiss.


    Let's say you got an overtaking manoeuvre wrong, and you needed to rev the engine to its maximum for a brief period. That is not the time to find out that it's redlined at 7000 but blows up at 5000. Think of it as the garage putting it through its paces so you don't have to. It won't damage the engine.
    If someone is nice to you but rude to the waiter, they are not a nice person.
    • Apodemus
    • By Apodemus 14th Oct 18, 8:23 AM
    • 1,163 Posts
    • 978 Thanks
    Apodemus
    As far as I'm aware, they rev the engine up to maximum ie. until the cut out operates, 3 times. I think that this is horrendous. They treat the engine in my car, in a way that I would never do.
    Originally posted by Thomas Crown
    Interesting! I wonder if it is possible to adjust the cut-out limit in the car’s configuration settings to minimise any risk of damage (and smoke) during the test?
    • AdrianC
    • By AdrianC 14th Oct 18, 8:43 AM
    • 19,709 Posts
    • 18,280 Thanks
    AdrianC
    Interesting! I wonder if it is possible to adjust the cut-out limit in the car’s configuration settings to minimise any risk of damage (and smoke) during the test?
    Originally posted by Apodemus
    If the car isn't capable of being red-lined without emitting excess smoke, then it's broken. It's that simple. And that's what the test is looking for. Your normal driving style is irrelevant to the test.


    B'sides, it's not under any load when being revved during the test - it's far more gentle on the engine than giving it throttle under load, such as dragging up a long motorway hill.



    You may not invoke ABS or traction control during your normal driving, either, but it still has to work, too.
    • Iceweasel
    • By Iceweasel 14th Oct 18, 8:52 AM
    • 4,361 Posts
    • 3,209 Thanks
    Iceweasel
    As far as I know the engine is not revved to maximum three times.

    It is revved to max only once to check that the governor is working.

    Then it may be revved to 2500 (or half the max revs if less than 2500) a maximum of six times if necessary to obtain readings for the smoke test.

    If it passes first time then there is no requirement to take further readings.

    This is what the tester's manual says:

    How to test:

    Make sure the engine checks are satisfactory.
    Make sure the engine temperature is above 80 degrees centigrade or at its normal operating temperature whichever is lower.
    Make sure you've removed any oil temperature probes.
    Increase the engine speed to around 2,500rpm or half the maximum engine speed – use whichever speed is lower.
    Keep the engine at this speed for 30 seconds – this should fully purge the inlet and exhaust system.
    Increase the engine speed slowly to maximum engine revolutions (revs) to check that the governor is working properly
    Once the engine speed has stabilized or it becomes clear that the governor isn't working, release the pedal and allow the engine to return to idle.
    Stop the engine and prompt the meter to do a zero check.
    Insert the meter fully and securely in line with the gas flow.
    Restart the engine.
    Following the meter prompts, press down the accelerator pedal quickly and continuously so that the engine reaches full fuel position in less than one second.
    Hold the engine at full fuel position until a release prompt is given and immediately release the accelerator pedal.
    Allow the engine and any turbochargers to return to idle.
    After the first acceleration read the smoke level displayed on the meter.
    If the smoke level is above the limit for the vehicle, carry out 2 further accelerations.
    If the mean smoke level is still above the limit for the vehicle, carry out further accelerations up to a maximum of 6 in total and read the smoke level display on the meter after each acceleration.
    The vehicle has passed the opacity test if any of the following happens:

    the first acceleration showed that the smoke level was at or less than the limit for the vehicle
    the mean smoke level from the first 3 readings was at or less than the limit for the vehicle
    the mean smoke level from any consecutive 3 readings was at or less than the limit for the vehicle
    If the smoke levels from the first acceleration were significantly higher than the limit, you can choose to abort the test.

    On vehicles fitted with a diesel particulate filter, also check that no visible smoke is emitted from the exhaust during the metered check.

    Engine malfunction indicator lamp
    Turn on the ignition and check that the engine malfunction indicator lamp (MIL) illuminates and then goes off. On some vehicles it will be necessary to start the engine before the MIL goes off.

    You need to inspect MIL fitted to diesel vehicles with 4 or more wheels and first used on or after 1 July 2008.

    Kit cars, amateur built vehicles and American pickups are not required to be fitted with an engine MIL.

    Defect Category
    Smoke opacity levels exceed the manufacturer’s specified limit.
    Major
    Smoke opacity levels exceed default limit
    Major
    Exhaust emits excessive smoke or vapour of any colour to an extent likely to obscure the vision of other road users
    Dangerous
    Exhaust on a vehicle fitted with a diesel particulate filter emits visible smoke of any colour
    Major
    Emissions test unable to be completed
    Major
    Emissions test aborted because smoke levels are significantly in excess of the specified limit values
    Major
    Engine MIL inoperative or indicating a malfunction
    Major
    • Nasqueron
    • By Nasqueron 14th Oct 18, 10:31 AM
    • 6,197 Posts
    • 3,779 Thanks
    Nasqueron
    Uh huh. However that wasnt my point - we were talking about the smoke test.

    And anyone with half a brain wont have removed the DPF (box), they've have taken it off, cut it open on the top, gutted it, welded it back up and refitted it. Then code out the DPF errors from the ECU.

    Practically undetectable.
    Originally posted by motorguy

    All they need is a test kit that picks up if the DPF isn't there due to exhaust output and problem solved. Whether such thing exists, who knows but there is still the black market of criminals and criminal drivers intentionally harming other people's health who deserve jail time.
    • Craig1981
    • By Craig1981 12th Nov 18, 6:18 AM
    • 560 Posts
    • 276 Thanks
    Craig1981
    just an update - car went for MOT, no issues at all (apart from a peeling indicator light bulb as an advisory)

    thanks all for comments and better understanding of the new tests - good to see different point of views
    • Scrapit
    • By Scrapit 12th Nov 18, 7:48 AM
    • 287 Posts
    • 91 Thanks
    Scrapit
    criminals and criminal drivers intentionally harming other people's health who deserve jail time.
    Originally posted by Nasqueron
    Bit of a stretch.
    • Johno100
    • By Johno100 12th Nov 18, 8:52 AM
    • 4,154 Posts
    • 4,942 Thanks
    Johno100
    Bit of a stretch.
    Originally posted by Scrapit
    Don't worry about Nasqueron he's one of Jeremy Vine's mob.
Welcome to our new Forum!

Our aim is to save you money quickly and easily. We hope you like it!

Forum Team Contact us

Live Stats

2,864Posts Today

6,485Users online

Martin's Twitter