New MOT rules on DPF removal

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  • New MOT rules on DPF removal
  • Premier Icon BigEaredBiker
    Subscriber

    Does anyone know what they are specifically going to check for or if there will be rules for cars of a certain age?

    https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter

    I drive a 2004 Pug 407 and had the DPF hollowed out and EGR bypassed after getting a very expensive bill to replace the DPF. The DPF is still there but it no longer does the job of a DPF.

    Anyone else looked into this before I call the garage and get their take? There is no way I am paying to reinstall a new DPF on a 10 year old car – which would be a shame as it’s been a good car.

    Apologies if this has been done before but the only thread I could find was a year old.

    Cheers

    BEB

    Wonder if that means Ill stop getting an advisory for having a plastic under tray every year as they will have to remove it to look.

    The documents linked from that page aren’t clear on whether you will fail if its just missing or fail if they test the exhaust and it has particulates in it that should be trapped by the DPF. Maybe Ill hold off removing mine a little longer!

    Premier Icon Northwind
    Subscriber

    Mine has a decat and I understand should fail, but it passes the emissions tests and the tester will only spot it if he knows exactly where to look, what he’s looking for, and most importantly can be bothered. I suspect this falls under the same umbrella. As long as it’s physically there, how will he know it’s hollow?

    The actual wording’s weak isn’t it… Do you have a filter, just modified, or is it modified to the extent that it’s not a filter?

    Premier Icon BigEaredBiker
    Subscriber

    I have a filter, but it was a drilled through. It would pass a visula check. Emissions tests on diesels are just a smoke opacity test as far as I know and it doesn’t sound like that is changing, but the doc is so woolly who knows?

    I *think* the opacity test was tightened a couple of years back for cars built after 2008 but again is still pretty liberal.

    Whatever happens I’m going back to a naturally aspirated petrol car, most of my mileage is expensed so trading in economy for reliability sounds like a good move.

    If the test is going to be really tight I am tempted to get an MOT done before the end of the month and then run the car for a year or breaks. Once its 11 years old it won’t be worth much so selling for scrap or low trade in won’t bother me too much.

    Premier Icon PePPeR
    Subscriber

    If the dpf is still there and hollowed out then you won’t have any problems as it’s only a visual check.

    Premier Icon BigEaredBiker
    Subscriber

    Hi PePPeR,

    Is that a fact backed by documentation, I’ve not seen anything yet? My MOT runs out in April so happy to MOT now rather than risk having a car that won’t pass without £600+ spending on it.

    Cheers

    joolsburger
    Member

    I find it quite weird that you guys seem happy for everyone to suck up the shit that’s coming out of the back of your oil burners, you are supposedly cyclists I’d have thought pollution would at least figure somewhere on your radar.

    Premier Icon 2unfit2ride
    Subscriber

    Joolsburger, a DPF does not magically get rid of the particles it filters, the cars software just chooses a time that it sees fit to do so, & in one big lump, so I don’t know if that changes your view of the matter or is of any help?

    Gribs
    Member

    However just about the only place you’ll get a DPF to regen is on a motorway or long dual carriageway, not really places you’ll find peds or cyclists to breath in the crap.

    sharkattack
    Member

    I find it quite weird that you guys seem happy for everyone to suck up the shit that’s coming out of the back of your oil burners,

    That took seven posts. The hand wringers are getting slack around here.

    Premier Icon PePPeR
    Subscriber

    https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter

    The MOT tester will get notification that your vehicle should have one the vehicle when they print the test sheet out.

    The tester will have to visually check its still there but that’s all they can do. If you have a filter thats been knocked out there’s no way of being able to check inside it.

    Me, I made damm sure I bought my wifes last car without one on it!

    2unfit2ride is right the car still dumps the particles but at the time it chooses to do so.

    I think it is and can only be a visual check as IIRC the MOT does not allow for any check that requires anything to be dismantled and reassembled. For the same reason I would be very surprised if anyone failed for running 100W headlight bulbs. Yeah, headlight function and alignment will be checked, but the actual bulb will not be taken out and examined.

    Premier Icon 2unfit2ride
    Subscriber

    The point I was making was you still get the same amount of soot in the atmosphere, but yes I see cyclists on main roads where cars could regen.

    Wonder if that means Ill stop getting an advisory for having a plastic under tray every year as they will have to remove it to look.

    They can’t remove/change anything, one wouldn’t even fold the back seat up in mine to test the seatbelts, just noted it as an advisory that seatbelts weren’t available to be tested. Although IIRC they can refuse to test it or fail it if they believe you’re hiding something. So an aftermarket undertray appearing where the DPF or CAT used to be might not pass.

    That took seven posts. The hand wringers are getting slack around here.

    I was thinking the same but bit my tongue, it is horrible cycling behind some diesels though in traffic.

    johnners
    Member

    “Hand wringers” is a bit of a poor effort IMO. You really need to throw in a “tree hugger”, a “yoghurt knitter” and maybe even a good old-fashioned “lentil-muncher” to really get those gobbets of spittle flying.

    Premier Icon molgrips
    Subscriber

    Joolsburger, a DPF does not magically get rid of the particles it filters, the cars software just chooses a time that it sees fit to do so, & in one big lump

    Wrong. It burns it off, into CO2. Collecting the actual soot to be released later would be next to impossible. Were you imagining a little door opening and a tiny housekeeper shaking out the filter as you drive along?

    However just about the only place you’ll get a DPF to regen is on a motorway or long dual carriageway

    Not really. The exhaust gas just has to be hot enough. Normally this would mean motorway but the engine has special ways of increasing the exhaust temperature artificially. It just needs enough time.

    Premier Icon 2unfit2ride
    Subscriber

    Does it not just burn off albeit at a higher temperature?
    I have regened lots of diesels and you defiantly get a big cloud of soot, but I may of missed the lump of carbon dropping on the floor 😉

    joolsburger
    Member

    Hand wringer? Not really, just someone who actually cycles and every so often sucks in a nice big mouthful of black smoke from some under maintained deisel shitbox.

    coffeeking
    Member

    Does it not just burn off albeit at a higher temperature?
    I have regened lots of diesels and you defiantly get a big cloud of soot, bit I may of missed the lump of carbon dropping on the floor.

    Not meant to, it saves up the deposits until they can be burned. I.e. consumed by combustion at a decent temperature, not just flushed out. IT would normally happen on the fly and in a continuing process but those who use their car start-stop a lot find the capacity of the DPF is limited and need to force a flush.

    There’s always a trade-off anyway, those facing amassive bill could scrap their old car and go buy a newly produced, newly carbon-financed machine that runs a bit cleaner but just cost christ knows how much pollution to build, it just happens to be away from the tailpipe.

    At the end of the day the general filtration of new tech into the market is going to happen no matter what, it makes little sense to police the few older cars that don’t get scrapped and are kept alive by mildly dodgy means IMO.

    Premier Icon aracer
    Subscriber

    wrote:

    Hand wringer? Not really, just someone who actually cycles and every so often sucks in a nice big mouthful of black smoke from some under maintained deisel shitbox.

    Though you don’t have to have a DPF to have a well maintained diesel which doesn’t emit clouds of noxious soot.

    I agree with molgrips – a DPF doesn’t emit the soot, it burns it off. My understanding is that motorway/DC isn’t required either – supposedly the threshold speed is ~40mph, and personally I get over that every time I drive.

    Thrustyjust
    Member

    Just think of all that green fail, when people scrap 5yr old cars to buy new ones , as the DPF repair is more than the cars value. All those cars being dismantled and nasty chemicals and oils etc. Great idea to get rid of pollutants, not, but the only real way is to not drive. I am sitting on the fence on removing my DPF , as forgot to ask my MOT man last month about it. The idea of a diesel is slow revving low consumption, but when you have to run at higher speeds for dpf cleaning, sort of wastes the diesel theory, as it injects neat diesel and eoloys to complete the cycle. Might just get a V8 petrol next to join the 24 mpg focus ST I have. 😉

    Gribs
    Member

    If you’re doing sustained 40+ speeds, I seem to remember about 10-15 minutes is needed, so you’re almost certainly going to be on a DC or a motorway.

    Premier Icon molgrips
    Subscriber

    It’s not the soot you can see that is the issue, the really bad stuff is invisible. That’s the stuff the DPF is there to filter out. And it’s an inevitable side effect of a diesel, it’s not caused by poor maintanence.

    Would you really scrap a £5,000 car for the sake of a £700 repair? Do you get rid of cars when their tyres wear out? Anyway when drivers and mechanics stop being so dense the bills will become much rarer. DPF blocked? Replace it, oh look it’s blocked again. Of course it is. Why is your engine producing more soot than normal and why is regen not working?

    nwilko
    Member

    visual dpf check, and existing smoke test.
    particulate testing is far too expensive and requires specific drive cycle under load which is not practical for uk mot.

    nwilko
    Member

    dpf actually makes more health issues as particulates remaining can travel deep into lungs compared to particle size pre dpf.
    another case of misguided legislation similar to death of lean burn gas engines.

    Thrustyjust
    Member

    Would you really scrap a £5,000 car for the sake of a £700 repair? Do you get rid of cars when their tyres wear out? Anyway when drivers and mechanics stop being so dense the bills will become much rarer. DPF blocked? Replace it, oh look it’s blocked again. Of course it is. Why is your engine producing more soot than normal and why is regen not working?

    There’s plenty of small diesels with 120 k on the clock worth pennies, so, sadly I believe people will get rid. As for scrapping cars when tyres are worn, if that’s the case, I wouldn’t have spent £300 on 2 tyres today on my 7 yr old diesel car….

    Premier Icon molgrips
    Subscriber

    I think most ‘failed’ dpfs are some other problem. Don’t see how it can fail, it’s just a filter.

    Premier Icon 2unfit2ride
    Subscriber

    The real problem lies with the modern use of diesel cars, they are simply not designed to be used predomantly in town or for short runs, it clogs the filter which is designed to clean itself at sustained higher temperatures, unfortunately they are sold as a cheaper car to own even though they are dearer to buy & the running & fuel costs are higher

    Premier Icon MrOvershoot
    Subscriber

    treaclesponge – Member

    Wonder if that means Ill stop getting an advisory for having a plastic under tray every year as they will have to remove it to look.

    Funny that one isn’t it, my car had its 4th MOT yesterday at the same garage and passed fine but its the first time they have put 2 advisory’s on the paperwork about undertray & engine cover, both OEM with the car.

    Premier Icon BigEaredBiker
    Subscriber

    A dpf is not a filter in the usual sense, nor is it quite like a catalytic convertor. Even if you drive all long motorway journeys and warm up the engine they can still become clogged, fail and put you in limp mode.

    One cause of this is that a regen (which is when you see all the soot blow out) uses a liquid, if that runs out you get no warning until you end up in limp mode.

    My 407 went from a 48 mpg average to 60 mpg once the dpf and egr were modified. Throttle response also greatly improved because the engine could now breath better. My car now never produces clouds of soot but yes it probably does chuck out the tiny particles you cannot see.

    Having now read up on diesels and owned one I will be going back to petrol once the 407 goes. Cleaner, simpler and IMHO nicer to drive.

    Funny that one isn’t it, my car had its 4th MOT yesterday at the same garage and passed fine but its the first time they have put 2 advisory’s on the paperwork about undertray & engine cover, both OEM with the car.

    Makes a bit of a mockery of the whole thing really.I get one every time, without fail. Essentially they cant see the first 50% of the exhaust so it could be rusting away nicely and be none the wiser. Does that mean that if you have steel wheels and filled in wheel covers the brakes cant be seen then they cant check the pad wear?

    I suspect that a modern diesel, even after having a DPF removed, is a lot cleaner than most 10+ year old diesels that I see chugging around with clouds of smoke around them. Oh and the portable diesel generator that turned Dartford into a foggy mess this morning.

    Premier Icon molgrips
    Subscriber

    The real problem lies with the modern use of diesel cars, they are simply not designed to be used predomantly in town or for short runs

    Thta’s not quite true. They are designed with this in mind, but you will get into trouble if you only do really really short runs. Or if you sit idling for ages If you drive around town all day you should be fine.

    One cause of this is that a regen (which is when you see all the soot blow out) uses a liquid, if that runs out you get no warning until you end up in limp mode.

    Only on some cars. If the DPF isn’t hot enough to burn off the soot, the car needs to make the exhaust hotter. Some cars (VAG) do this by squirting fuel in the exhaust stroke, and a catalyst combusts these unburned hydrocarbons to increase the temperature enough to then burn the soot out of the DPF. Other cars (Peugot and Ford/Mazda) need this additive to do the job instead, and the catalyst is integrated into the filter.

    My 407 went from a 48 mpg average to 60 mpg once the dpf and egr were modified

    It’ll also be producing loads more NOx too, which is a harmful irritant and causes smog. Nasty stuff.

    I suspect that a modern diesel, even after having a DPF removed, is a lot cleaner than most 10+ year old diesels that I see chugging around with clouds of smoke around them

    Probably not, it’s probably the same. The engines work in the exact same way – squirt diesel into hot air – so if they are running at low load the results will be the same.

    If you go back 20 years then injector pressures were lower and fuel atomisation wasn’t as good, so at higher loads they produced more smoke, but under normal driving there’s plenty of air in there so the fuel droplets combust more or less completely. That’s why older diesels originally had much bigger displacement than equivalent petrol engines – more air to spread the fuel around in = less smoke.

    If you floor a diesel from low revs there’s a moment where the turbo isn’t spooled up, so the ECU (to improve driveability) dumps extra fuel in there which doesn’t burn completely, but still burns a bit to get the turbo going. This results in the puff of smoke you used to see. And I suspect that eco label diesels don’t do this, which is why the reviews said that they had less low-end punch.

    gonzy
    Member

    errrr….would it not be easier to ring up a few random MOT test stations in the area and ask them how they test diesels and what they look for? 😯

    I’ve got a 90K 3 year old BMW 320d and it don’t smoke one bit. It probably spits out cleaner air than it sucks in…

    My car before that was a Toyota Avensis, when the outside temp got near 2 degrees or less it would idle at 1000rpm, I took it to garage and it’s an emissions control thing apparently, Rev’s highly to keep the coolant temperature up to prevent DPF from clogging up. Net result was it was doing 35mpg instead of reliable 42mpg, hardly protecting the environment is it’s using loads more fuel!

    Premier Icon aracer
    Subscriber

    Mreay wrote:

    Net result was it was doing 35mpg instead of reliable 42mpg, hardly protecting the environment is it’s using loads more fuel!

    Depends which part of the environment you’re trying to protect.

    Premier Icon molgrips
    Subscriber

    How long were you spending at idle for it to drop your fuel economy that much?

    Anyway as has been said, this interrim technology is going to be replaced with something better in a few years time which will solve a lot of the problems.

    Inbred456
    Member

    Car speed has nothing to do with when a car regens its dpf, its mostly to do with exhaust temperatures due to engine revs. When the engine is cold the unburnt carbon from the combustion process is trapped by the dpf. When the engine is warm and the exhaust temps high enough the management system will trigger a regeneration process by altering the timing and ignition to burn the carbon and turn it into ash to be stored in the filter. When the filter is full its full and needs replacing. Lots of short journeys at low revs means more carbon in the filter full stop. Most modern diesels are so high geared that the revs never get high enough even on a motorway to regen fully. Manufacturers are moving the dpfs closer to the exhaust manifold to increase the efficiency of them but that leads to all sorts of design problems in the engine bay. Most regens are triggered at engine revs over 2000rpm and need at least 20 to 30 mins. If I was to buy a modern diesel it would be a year old and I would get shot at 4yrs old circa 60k.

    johnners
    Member

    trigger a regeneration process by altering the timing and ignition to burn the carbon and turn it into ash to be stored in the filter

    I don’t think that can be right. If you burn carbon in air you’ll get carbon dioxide and water.

    Inbred456
    Member

    Your heating the carbon with the exhaust gases not air. There is no combustion taking place in the dpf just a heating process to convert the hydrocarbons to ash. The oxygen has been used in the cylinder when the charge combusts. What ever oxygen is left it must be CO2 and CO surely.

    Premier Icon aracer
    Subscriber

    Oxygen is present in diesel exhaust at sufficient concentrations at practically all operating conditions.

    http://www.dieselnet.com/tech/dpf_regen.php

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