How to roll coal??

[Darwin1138]

I know that you can make "performance" upgrades to a Diesel to make it smoke, but, in a stock car, what system or parts need to fail or be under-serviced to make it smoke??

I ask this because I was in a shop because of a broken wheel and while I was waiting, a costumer came to pick up his car, a MKV Jetta TDI, apparently they perform a full service on his car (oil, filter, air filter, fuel filter, clean injectors and what not), then the costumer asked about the smoke issue an the technician said: "That is completely normal, because it is a Diesel, and because of the high mileage of your car, soon we will have to rebuild your engine but since it still develops plenty of power we can wait a little longer" . Then the costumer asked if the smoke will stop when the engine is rebuilt and he said: "It will be less but it will still produce smoke because the Diesel engine operates in that way"

I chatted a little bit with the costumer, saying that I wanted to buy a car like that and other trivial things, just to take a look at the odometer. The car only had 115,000 km!!!

Then the costumer departed and sure enough a little cloud of smoke came out of the tailpipe. I expected the smoke to be blue, as if the engine was burning oil, as the technician had implied earlier; but the smoke was black and smelled like diesel.

I don't think these cars had a DPF but I am sure it should not be smoking like that. So why an apparently "serviced" car with low mileage and without tuning modifications produces smoke like that??? Are these engines computer controlled, with an oxygen sensor or some other type of sensor, like a fuel injected engine or they use a mechanical open loop system like a carburetor??

 

[901Memphis]

Why do diesel engines smoke?
Diesel engine smoke is caused by incomplete combustion. White smoke is caused by tiny droplets of unburned fuel resulting from engine misfiring at low temperature. This smoke should disappear as the engine warms up. Black smoke could be caused by a faulty injector, insufficient air and overloading and/or over-fueling the engine. Blue-gray smoke is the result of burning lubricating oil and is an indication the engine

 

[440Magnum]

Its actually tricky to make a diesel *not* smoke. Any diesel with purely mechanical fuel injection is prone to smoke, because as you advance the throttle the fuel injection rate goes up in direct proportion to throttle position, before engine speed and turbo boost have a chance to "catch up." With full electronics and either common-rail injection or a HEUI type system, the fuelling rate can be tailored so that it doesn't slug the system when you move the pedal, and smoke is greatly reduced. Older VWs (even up into the 2000s) were just naturally a little smoky. Volvo diesels, too, remained smoky longer than some other brands. Prior to the early 90s, though, ALL diesels were smoky- enough that it would really stand out in today's traffic with mostly much cleaner diesel cars and particulate-filtered diesel trucks.

 

[SteveSRT8]

Older diesels do not have the ultra high pressure fuel injection and exhaust particulate filters that newer models have.

My 09 Duramax never emits anything visible...

 

[Darwin1138]

Originally Posted By: 440Magnum
Its actually tricky to make a diesel *not* smoke. Any diesel with purely mechanical fuel injection is prone to smoke, because as you advance the throttle the fuel injection rate goes up in direct proportion to throttle position, before engine speed and turbo boost have a chance to "catch up." With full electronics and either common-rail injection or a HEUI type system, the fuelling rate can be tailored so that it doesn't slug the system when you move the pedal, and smoke is greatly reduced. Older VWs (even up into the 2000s) were just naturally a little smoky. Volvo diesels, too, remained smoky longer than some other brands. Prior to the early 90s, though, ALL diesels were smoky- enough that it would really stand out in today's traffic with mostly much cleaner diesel cars and particulate-filtered diesel trucks.


This car wasn't an older car, probably was a 2010 or 2011 model, it even had a DSG transmission, and IIRC those engines are common rail.

Maybe I should rephrase the question: What has to fail in order to make a full electronics common-rail injection engine to smoke??

 

[Thermo1223]

Well on the common rails if there was visible over fueling like that all exhaust after treatment would have to be removed or disabled in some way. I say that because if it wasn't it life would be greatly shortened.

My guess is it was a 2.0 PD with maybe a bad turbo actuator but even so the ECU keeps tight regulation on fueling.

Someone purposely had to modify the ECU to really get it "roll coal".

Either way the garage sounds horribly suspect as the injectors would not need to be even touched so early in the cars life. 115,000km is as you stated not high mileage. I would be extremely weary of taking any car there in the future. Like most USA shops & dealers they haven't the first clue on how to service a TDI.

 

[440Magnum]

Originally Posted By: Darwin1138
Originally Posted By: 440Magnum
Its actually tricky to make a diesel *not* smoke. Any diesel with purely mechanical fuel injection is prone to smoke, because as you advance the throttle the fuel injection rate goes up in direct proportion to throttle position, before engine speed and turbo boost have a chance to "catch up." With full electronics and either common-rail injection or a HEUI type system, the fuelling rate can be tailored so that it doesn't slug the system when you move the pedal, and smoke is greatly reduced. Older VWs (even up into the 2000s) were just naturally a little smoky. Volvo diesels, too, remained smoky longer than some other brands. Prior to the early 90s, though, ALL diesels were smoky- enough that it would really stand out in today's traffic with mostly much cleaner diesel cars and particulate-filtered diesel trucks.


This car wasn't an older car, probably was a 2010 or 2011 model, it even had a DSG transmission, and IIRC those engines are common rail.

Maybe I should rephrase the question: What has to fail in order to make a full electronics common-rail injection engine to smoke??


If its that new, then I think it should have particulate filtration (I'm not totally familiar with when VW phased them in) and shouldn't emit visible smoke even if the engine is smoking like mad upstream of the filter. But the filter will plug repeatedly and have to "regenerate" constantly if the engine's producing very much smoke.

Common-rail injection will still smoke a *little*, otherwise there would be no need for DPF's. But even without a DPF it should rarely be visible. Changing the fuel programming in the ECU will do it. A bad turbo, bad manifold pressure sensor, other bad sensors could all do it. But it should be throwing codes out the whazzoo if its got bad sensors.

 

[Nick1994]

Totally normal. My aunts 04' VW TDI has always smoked, and when not washed regularly has a dark has on the back

 

[weebl]

Originally Posted By: Nick1994
Totally normal. My aunts 04' VW TDI has always smoked, and when not washed regularly has a dark has on the back


Yes, but the '04 PD engines are a completely different animal than the '10/'11 common rails. '04 would have been before all of the modern gadgetry required of modern diesels.

 

[eljefino]

I highly suspect your diesel cars have a "Mexican tune" and very few gizmos we expect in the States. They'll have nearly as advanced computers and power abilities, just the firmware won't demand all sorts of emissions concessions. The transmission might be the same because, hey, they already paid the R&D on it.

Also, how's the fuel?

 

[expat]

About 20 years back there was an 80's VW Rabbit Turbo Diesel for sale near here, a really nice car but it smoked.
I knew someone that was looking for an economical car, she liked it but wanted to get the smoke checked out.

We found a local VW Diesel guy that said 'No problem" she bought it, and he Fixed it for $50, I did not know what he did, but the car ran fantastic for the next 5 years, smoke free!

 

[artificialist]

Originally Posted By: expat
About 20 years back there was an 80's VW Rabbit Turbo Diesel for sale near here, a really nice car but it smoked.
I knew someone that was looking for an economical car, she liked it but wanted to get the smoke checked out.

We found a local VW Diesel guy that said 'No problem" she bought it, and he Fixed it for $50, I did not know what he did, but the car ran fantastic for the next 5 years, smoke free!


There are some fuel injection cleaning additives that may have been used. Stanadyne brand diesel additive is common.

For the OP's electronically controlled diesel, if it blows that much smoke and has no modifications, check the computer for codes, check the turbo system for boost leaks, and see if the intake manifold has a large amount of soot in it.

And running some diesel fuel injection cleaner can help.

 

[Darwin1138]

Originally Posted By: Thermo1223

Either way the garage sounds horribly suspect as the injectors would not need to be even touched so early in the cars life. 115,000km is as you stated not high mileage. I would be extremely weary of taking any car there in the future. Like most USA shops & dealers they haven't the first clue on how to service a TDI.

Yes, the garage was really bad, I was there only because I went to get a quote for a new tire that I need, after the guy of the TDI left they told me that they didn't had the correct size (195/55 R16), but that I could use a little bigger tire (205/60 R16), to which I replied: "Wouldn't that make the car behave differently?" and they said "No, no way, we do that all the time and we haven't received any complaints". I said thanks and got out as fast as I could.

 

[Darwin1138]

Originally Posted By: eljefino
I highly suspect your diesel cars have a "Mexican tune" and very few gizmos we expect in the States. They'll have nearly as advanced computers and power abilities, just the firmware won't demand all sorts of emissions concessions. The transmission might be the same because, hey, they already paid the R&D on it.

Also, how's the fuel?


Yes the car had a Mexican Tune but not from the factory because at least in paper there are some emission limits, for example, in in the petrol powered cars the emission limits for a new car are 100 ppm of HC, 0.6% of CO and 1000 ppm of NOx, which for a small car (1.0L to 1.6L) roughly translates as a EURO IV emission standard; for bigger engines these same limits are the equivalent of a higher Euro level of pollution. I don't know the limits for the Diesel engines but they must be similar. What I can tell you is that I have seen other Jettas TDI and an Audi A3 TDI an none of them smoked like that one.

But that doesn't matter too much, because although all the cars from the factory are at least EURO IV, they are maintained by a bunch of incompetent mechanics that think that the best oil is a SAE 60, that remove the thermostat and the coolant cap, remove the oxygen sensors and do many other lunacies; and as a result of that any car in Mexico with more than 100,000 km. is ready for the crusher.

So the most probable theory is that some clown made a "special modification" or something went wrong with the car and they choose to ignore the problem. And as 440 Magnum said the DPF plugged constantly and then they decided that the DPF was the problem and simply removed it.

The diesel fuel is low on sulphur although I don't know how low. In petrol there are two types: 1) Magna 87 AKI 300 PPM sulphur and 2) Premium 92 AKI 50 PPM sulphur.

 

[asand1]

Intake was probably choked up with carbon causing a rich condition.