2.0 TDI Smoke? Troubleshooting Acceleration Issues

Hello everyone,

I need a little help and would appreciate your experiences with a rather trivial topic.

It's a 2.0L 100kW Piezo-4V TDI engine with the original software, installed in a Passat with a DSG transmission (Belgian version without DPF), manufactured in 2008, and with 150,000 kilometers on the odometer.

When accelerating with a vehicle equipped with a diesel particulate filter (DPF) in normal city traffic, a massive, jet-black cloud forms, obscuring half the road behind me. It's not the usual diesel exhaust smoke.
No oil or water consumption, no blue smoke, and no other noticeable issues.

Well, I thought to myself - the amount of air entering the combustion chamber is determined by the smoke limit - so it must be the mass airflow sensor. I replaced it, but it didn't fix the problem.

Before I start reading the error codes and logging data while driving, what are some typical defects in 2.0 TDI engines that can cause excessive smoke?

Greetings.

There are problems in the boost pressure system. Including a repair kit for the hoses. It might be the same issue for you. } If you log the data, you can see it. }

mullemaus wrote:

There are problems in the turbocharger boost system. Including a repair kit for the hoses.

It might be the same issue for you. You can check by logging the data, and then you'll see it. }

Is there a known issue with leaks in the LLK section?

No, with the N75 or Lader control .

mullemaus wrote:

No, with the control unit N75 or turbocharger

Hmm...as long as "only" the boost pressure is not regulated correctly and the rest of the hardware is okay, a TDI shouldn't produce excessive soot. Because the soot limiter is there precisely to prevent that.

However, each type of soot reduction method has its own specific limitations.
With air mass as an input, charge air leaks can cause abnormal soot formation.
When using boost pressure as an input, restrictions in the gas flow path behind the boost pressure sensor (e.g., a stuck throttle valve, excessive EGR buildup, worn camshafts, pinched/blocked catalytic converters...) can lead to increased soot formation.

Thanks for your initial feedback. I'll log in tonight and then we can discuss it further.

"By the way, I'm not familiar with the SIMOS engine control unit software. Is the smoke limitation here implemented like it used to be in BoschEDC 16/15, as a simple map based on corrected air mass (from the mass airflow sensor) and engine speed? Or is there something else involved, such as boost pressure (from the boost pressure sensor), calculated lambda (possibly from an air model since there's no lambda sensor installed), or even a modeled air-fuel ratio (as is common nowadays) as an input parameter?"

Does anyone know anything about that?
It seems that the measurement data blocks on the "Mess-Can" contain the same parameters as those found in the Bosch EDC16 engine control units. Therefore, they probably have similar software structures to Bosch, right?

Greetings.

I just measured the piezo element in my SIMOS device.
"Who can spot the mistake?"


It seems not everything is compatible like the Bosch EDC16 units.

Hello,

The column names for the start date of the funding are incorrect.
Furthermore, the intended start date for the funding is too late, assuming that the values in column K should be included (which measurement data block?).

Best regards, Rainer.

Your boost pressure and duty cycle are completely unacceptable.
What's going on?



1424 2024 2092
1449 2105 2137
1485 2183 2184
1514 2195 2234
1545 2201 2285
1571 2210 2339
1598 2221 2388
1619 2238 2401
1655 2255 2381
1670 2265 2372
1714 2277 2380
1725 2290 2407
1772 2298 2438
1803 2304 2458
1832 2310 2468
1861 2315 2458
1882 2320 2439
1916 2327 2421
1925 2333 2407
1971 2339 2400
1990 2346 2398
2026 2346 2397
2035 2346 2398
2071 2346 2401
2105 2346 2400
2134 2346 2401
2160 2346 2408
2187 2346 2417
2205 2347 2428
2227 2347 2440
2259 2347 2450
2283 2347 2460
2313 2347 2468
2330 2347 2479
2367 2347 2490
2391 2347 2500
2420 2347 2509
2449 2347 2519
2475 2347 2520
2502 2347 2520
2516 2343 2530
2549 2341 2530
2574 2333 2530
2588 2329 2540
2617 2327 2540
2626 2320 2540
2657 2317 2540
2693 2312 2540
2711 2308 2540
2730 2303 2530
2755 2296 2530
2782 2294 2519
2802 2287 2509
2820 2286 2490
2825 2282 2479
2854 2278 2460
2881 2274 2440
2894 2269 2421
2917 2264 2401
2934 2263 2387
2944 2257 2366
2974 2253 2349

@Rainer,

Sure, column D represents "Förderdauer" (grant duration), which corresponds to MWB 1.3, just like column L represents the same in MWB 4.3.
Column K actually refers to MWB 4.2, which indicates the start of funding.

"Is the start of fuel delivery too late? I'm not familiar with the PD (presumably referring to a specific component), but I don't find 6° KW before top dead center (TDC) at 2000 RPM and 14° KW before TDC at 4000 RPM at full load to be unusual. Does the comparable competitor or Bosch have different fuel delivery start timings at full load?"
"An idle speed of 4.2° KW after TDC (Top Dead Center) and a slight deviation after TDC at partial load, I consider to be normal."

Here's the corrected log with data from partial load trips.

Where exactly are you seeing the late injection?


@Mullemaus,

Okay, the turbine guide vane position is stuck in a closed position between 2000-2800 RPM during this acceleration. There is no error condition yet, but I also have measurements that indicate the measurement range of the LD sensor is insufficient.

What else do you find unacceptable about the charging pressure/VTG-TV system?
- Den Soll-Ladedruck? "Where exactly?"
- The build-up/release of boost pressure.
- The behavior of LD-compliant vehicles (excluding VTG-compatible wagons)?
- Das VTG-Ansteuer-TV, nach Einregelung? "Where exactly?"
- Is the VTG control TV in the drawer?


...and why is the cabin now smoking so much when accelerating?

Greetings.

@Mullemaus,

Okay, the turbine guide vane position is stuck in a closed position between 2000-2800 RPM during this acceleration. There is no error condition yet, but I also have measurements that indicate the measurement range of the LD sensor is insufficient.

What else do you find unacceptable about the charging pressure/VTG-TV system?
- Den Soll-Ladedruck? 'Where exactly?'
- The build-up/release of boost pressure.
- The behavior of LD-compliant vehicles (excluding VTG-compatible wagons)?
- Das VTG-Ansteuer-TV, nach Einregelung? 'Where exactly?'
- Is the VTG control TV in the drawer?


...and why is the cabin now smoking so much when accelerating?

Greetings

I would attribute the smoke to the non-engaging turbofan thrust limiting system. If it overshoots like that, it won't limit the thrust as it would with a properly functioning VTG (Variable Thrust Geometry) system.

bafische wrote:

The turbine guide vane mimic is stuck in a closed position, with undefined behavior, between 2000-2800 RPM during this acceleration. ....and why is the engine smoking so much when accelerating?

If the smoke limit is calculated from the boost pressure, I see the clear answer in a (EDC15-) parallel case:
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
The logs show how the extreme back pressure in the exhaust system severely restricts the air exchange, causing the air-fuel ratio (which is the basis for the light scattering calculation dependent on the light density!) to drop to approximately 53% of its normal value.
A lack of air of up to 47% compared to the baseline calculation -> it's logical that a vehicle with a smoke reduction system dependent on load would produce excessive soot.

Hello Mulle,

Quote:

I would attribute the smoke to the non-engaging turboshaft speed limiter. If it overshoots so high, it won't limit it like a properly functioning VTG (Variable Turbine Geometry) system would.

It's a different control unit, but then almost every BKD engine would fail.
Apart from that, there's no reason for the engine to produce black smoke, as there's plenty of air available. @Ulf, also see the air mass readings; if there's no leak, this air is actually passing through the engine.
"The boost pressure control isn't working properly, that's true. I don't think it's the cause of the smoke. Also, the delayed fuel injection start that I suspected seems unlikely; who would intentionally mess up the data like that... and the synchronization angle is still within range. It should be much earlier, though; I'll check that later."

What exactly does the idle speed control do, and is a nozzle dripping?

Best regards, Rainer.

Quote:

I would attribute the smoke to the non-engaging turboshaft speed limiter. If it overshoots like that, it won't limit the speed as it would with a properly functioning VTG (Variable Turbine Geometry) system.

Do you mean that the LM/LD (likely referring to lambda/load values) and injection quantity are no longer in sync in the "overshoot" phase, or that, due to the emission regulations regarding injection duration, the injection takes too long, and this ultimately leads to smoke formation?
hg
Herbert.

Perpetrator found.

It was the mass flow meter. But it wasn't easy to explain at first.

So, immediately after replacing the catalytic converter, I still saw black smoke coming out the back when accelerating after a period of low load driving. I did a couple of accelerations and then, frustrated, I put the car away – I thought I had wasted 100 euros on the catalytic converter.
I then posted in this forum and spent hours looking at the logs, and like all of you, I couldn't find a simple solution.

Jetzt bin ich den Wagen mal wieder gefahren und siehe da, mit jedem Kilometer wurde die Rauchwolke geringer - bis nach 1h Autobahnhatz kein noch so schwaches Wölkchen hinten rauskam, trotz stundenlangem Stadtfahren. Huh, I thought.

Okay, I logged everything properly and reinstalled the old HFM... and it kept getting darker and darker until I saw a completely black screen when accelerating. I logged everything again.

After comparing the logs from the "old" and "new" HFM (mass airflow sensor), it was observed that, under partial load conditions, the "old" HFM exhibited significantly higher EGR (exhaust gas recirculation) temperatures and slightly lower boost pressures, while maintaining the same measured airflow and the same VTG (variable turbine geometry) temperature. In effect, this meant higher EGR rates and, consequently, lower oxygen concentrations in the intake air with the old HFM. This resulted in noticeable black smoke and, apparently, significant particulate buildup in the catalytic converter and EGR system. When accelerating from this partial load condition, all of this accumulated "dirt" was then expelled.

As a pleasant side effect, the car feels incredibly responsive with the new HFM, not in terms of top speed, but during normal acceleration from cruising speeds. Even my wife, who usually only notices something if someone has removed the engine, noticed it.
Given that it's currently delivering power up to 2200 RPM, I highly doubt there's any active turbo boost limitation in the data. The torque gradient in first gear is enormous here. Nowadays, such behavior wouldn't make its way into a production model.

Given that the car is only used in the city and for short distances, it's no surprise that the VTG (variable turbine geometry) is stuck, especially if it was often operated at partial load with smoke levels in the "brick" range. I don't even want to know what condition my intercooler, intake manifold, turbine, exhaust manifold, and catalytic converter are in.
Poor DPF-equipped vehicles. This defect isn't noticeable due to the plug in the exhaust, and it constantly clogs the filter and turbine under partial load – resulting in poor fuel economy and a high likelihood of the VTG (variable turbine geometry) seizing.

@Rainer, your initial impression was correct - after comparing with some BKP logs, my production start is significantly later, I would generally say about a 5°kW offset across the entire KF.
I noticed that the BKP (likely referring to a specific engine component or system) advances the timing at idle, and at 4000 RPM, the valve timing is at approximately 18° KW before top dead center (TDC). This is significantly earlier than mine.
Is the BKP also a SIMOS? If not, do other EU4 SIMOS concepts also have earlier start dates?

Can adaptation cause any problems? I mean, for the start of fuel injection, there's no adaptation option available for the 2.0 TDI engines with EDC16.

By the way, LRR was consistently below 1mg/hub for all integrators. Environment: 1000 mbar air pressure, 12°C ambient temperature.

I hope this report helps other people who are seeking assistance with troubleshooting. So, don't immediately start looking for new errors if the stove is still smoking right after the HFM (High-Frequency Mixer) replacement.

Best regards,

Hello,

Quote:

... I noticed that the BKP (likely referring to a specific engine component or system) advances the timing at idle, and at 4000 RPM, the valve timing is at approximately 18° KW before top dead center (TDC). This is significantly earlier than mine. Is the BKP also a SIMOS? If not, do other EU4 SIMOS concepts also have earlier start dates? Can you mess something up through adaptation? I mean, for the start of the boost, there is no adaptation option for the 2.0 TDI engines with EDC16.

I just checked, and normally at 4000 rpm and full load, the fuel injection starts around 20° BTDC (Before Top Dead Center).
To the best of my knowledge, an adaptation is not possible in this case.

Best regards, Rainer.