Smoke belching diesel vehicles.

BikerGroveish

I’ve been riding today and my route has included passing through a couple of towns. I was behind a car which was belching a lot of smoke from the exhaust. I thought the MOT checks for this now. I guess it’s not got an MOT or it would fail one if it went through now. I ended up looking like a coal miner from the 1950s. That can’t be good.

akh

Emissions are tested on an MOT (my car got an advisory for them on its last test).

You don't need to wonder if a vehicle has an MOT, you can check the status with the DVLA online (assuming you know the registration number, which I assume you don't in this case). Also handy for checking your own. At no point does it say you need to be the owner or keeper, or have their permission, to check, which seems valid, as it's a legal requirement and it's on a public road.

https://vehicleenquiry.service.gov.uk/

Of course it may not have been MOT'd correctly, or developed a fault after the MOT. Plus (as VW proved) the test and real world emissions are chalk and cheese.

super_davo

I'd expect the car had a clogged Diesel Particle Filter. Looks really bad but isn't that serious, caused by lots of short journeys where the exhaust doesn't get a chance to warm up and cured by giving a good run on a motorway. So perfectly possible that when the car did the MOT it was fine.

Usually an indicator that people drive in conditions where it would be much more sensible to use a bike. It never happens to my diesel that only gets used for long journeys but happens frequently to my Mrs when she uses for the school run a mile and a half down the road.

mr_mojo

Not all diesel cars have DPF, I have a 2008 Mercedes C Class that doesn’t as it’s Euro 4, kicks a cloud out of the exhaust if you boot it too. It will still pass its next MOT as the new smoke rule doesn’t effect me as no DPF.

The new smoke rule only apply to cars with DPF fitted from new, Euro 5 and newer.

StillGoing

super_davo wrote:

I'd expect the car had a clogged Diesel Particle Filter. Looks really bad but isn't that serious, caused by lots of short journeys where the exhaust doesn't get a chance to warm up and cured by giving a good run on a motorway. So perfectly possible that when the car did the MOT it was fine.

Usually an indicator that people drive in conditions where it would be much more sensible to use a bike. It never happens to my diesel that only gets used for long journeys but happens frequently to my Mrs when she uses for the school run a mile and a half down the road.

I have to use my 2013 Touareg Euro 5 for short journeys fairly often, but I make sure it gets driven like I stole it once a month to ensure the DPF gets hot and burns any soot residue off. I recently had it checked by Engine Carbon Clean and it came back with some of the best figures they've seen. The MOT is due this week so we'll see what bill of health they give it too.

http://www.enginecarbonclean.com/

BikerGroveish

This was a 2003 Ford Mondeo. It wasn’t just a small cloud of smoke on hard acceleration either. It was a constant plume like an injector was out or the turbo had blown.

ugo.santalucia

super_davo wrote:

I'd expect the car had a clogged Diesel Particle Filter. Looks really bad but isn't that serious, caused by lots of short journeys where the exhaust doesn't get a chance to warm up and cured by giving a good run on a motorway. So perfectly possible that when the car did the MOT it was fine.

Usually an indicator that people drive in conditions where it would be much more sensible to use a bike. It never happens to my diesel that only gets used for long journeys but happens frequently to my Mrs when she uses for the school run a mile and a half down the road.

This...

diesel engines are managed by a computer, at intervals the computer decides it's time for a "cleaning cycle" of the DPF, which results in the emission of a cloud of soot... it is horrendous and I am not sure how they got away with that one... but that's it

captain_chaos

ugo.santalucia wrote:

super_davo wrote:

I'd expect the car had a clogged Diesel Particle Filter. Looks really bad but isn't that serious, caused by lots of short journeys where the exhaust doesn't get a chance to warm up and cured by giving a good run on a motorway. So perfectly possible that when the car did the MOT it was fine.

Usually an indicator that people drive in conditions where it would be much more sensible to use a bike. It never happens to my diesel that only gets used for long journeys but happens frequently to my Mrs when she uses for the school run a mile and a half down the road.

This...

diesel engines are managed by a computer, at intervals the computer decides it's time for a "cleaning cycle" of the DPF, which results in the emission of a cloud of soot... it is horrendous and I am not sure how they got away with that one... but that's it

No - the DPF captures particles - its a filter. When it regenerates the exhaust gas is made hot enough (via control of engine parameters) that the trapped particles burn off (convert to gaseous emissions) - you do not get a plume of soot. Emission regulations measure at tailpipe - not engine out. Therefore if your strategy just creates a cloud of soot periodically as Ugo says you will fail legal compliance and not be allowed to sell your vehicle - it will be captured at the Certification phase which is witnessed by the authorities (which in light of post VW is now ~5-10 times more demanding for the manufacturer)

Big clouds of soot are due to improperly maintained or faulty engines and sub-systems - faulty injectors, failed turbos, dirty air filter etc. Or people illegally removing the DPF

mr_mojo

I’ll repeat myself, not all cars especially the older diesels have DPF fitted including this 2003 Mondeo. They only really became a common factory fitted component about 2008/09. Hence clouds of smoke, just a Diesel engine thing regardless on how well it is maintained.

peat

My Mondeo is pretty smokey on start-up, better since I changed the fuel filter, but still smelly.

It failed it's MOT, but not because of the new emissions regs....

keef66

My 2 year old A1 seems to regenerate it's DPF pretty frequently. I know it's part way through a cycle when at the end of a short journey I get out to find it smells like it's overheating and the fan's going full blast.

At first I thought it was a fault but it seems it's normal behaviour. During regeneration the DPF gets pretty hot, and there's not a lot of room in the engine compartment so the fan has to keep running to disperse the hot air and prevent damage to other underbonnet components. It doesn't emit any soot; the tailpipe's as clean as a whistle.

Barring turbo failures, oil seals and injector faults, 99% of the worst offenders are poorly maintained older diesels, often buses. You can report certain vehicles, but not cars.

I once had a non turbo diesel Cavalier. Acceleration was glacial, and if ever I got impatient and dropped a gear and floored the accelerator it would produce an obscene amount of smoke, a lot of noise, and no discernible effect on speed....

StillGoing

Just had my VW Touareg 3.0 V6 Tdi done. Result of FAS test was 0.29 way below permitted level of 0.6.