PD Motor Problems: Common Issue or Defect? | Posts 16+

Hello,

It's often said that PD engines generally don't rev as freely as VP-TDIs, and that they produce very little power above around 3500 rpm.

Meanwhile, I'm wondering where this prejudice might come from.

Okay, most PDs (Performance Diesels) have a more pronounced torque peak than VPs (Variable Pressure Diesels), meaning a greater ratio between the torque at maximum power and the torque at rated power.

The biggest drop is seen in the 85 kW models with 310 Nm of torque. The ratio of 310:201 Nm means that the acceleration between 2000 and 4000 rpm decreases by a significant 35%, which is about twice as pronounced as in the 81 kW version with a ratio of 235:193 Nm, representing an 18% loss.

The ASZ engine, with its torque figures of 310 Nm and 229 Nm, resulting in an approximate 26% loss, might be considered to have a restricted power output at higher RPMs.
Even I noticed something from the factory: during the dyno test, my engine became noticeably less responsive above 3500 rpm compared to below that speed.
However, this characteristic has clearly disappeared since I corrected the NW setting to the target value. Now, it no longer resembles the AFN in any way, subjectively speaking.
The error was approximately 3° KW in the late direction.

I can even imagine this being a mass production defect.
If the crankshaft locking pin is placed on the gear, and then the engine is turned forward with some force (because it needs to happen quickly), until the locking pin engages and blocks the movement, then, in my opinion, elastic or plastic material deformations could occur, causing the crankshaft to stop only after the actual top dead center (TDC) position is reached.

Each tool needs some clearance to allow it to be easily attached and detached. In the case of the small crankshaft gear, even a small amount of clearance in the crankshaft stop results in a relatively large amount of angular play.

Adding deformations and tolerances, the total error likely grows quickly into the single-digit degree range, in my opinion.

If the NW wheel is then adjusted as if the KW wheel were at top dead center (TDC), the misadjustment is complete, and the engine will appear more or less reluctant to turn, depending on the magnitude of the error (the same thing can, of course, happen during a timing belt replacement at an authorized service center).
In the average scenario for all PDs, a late implementation of Northwest (NW) technology would likely occur, which could explain the often-expressed perception that PDs become less effective over time.

Even engines that are poorly tuned seem to sometimes pass tests. For example, the Fabia RS was found to have a torque loss from the factory during testing, resulting in a power output of just over 120 horsepower instead of the expected 130.
(I downloaded the test as a PDF from the Hopa website in January. However, Hopa is apparently offline at the moment, and the PDF is a bit large, over 3 MB, so it's probably not suitable to attach.)

Okay, but most of that is just speculation. The only thing I know for sure is the engine's performance before and after.
What does the rest of this group say about my theory?


Hello Ulf,

Okay, so I'm driving something like the original PD model, which I've mentioned before, but maybe it was too early to talk about it.

AJM engine (with '285 Nm of torque as an 85 kW engine' in a Passat Variant Comfortline with a 5-speed transmission) was purchased with approximately 20,000 km on the odometer, and was primarily used for long-distance driving.
Federal roads / highways, approximately 100 km per day.

I've now, out of sheer desperation, had an OBD engine control unit software update performed. Supposedly, it now has around 150 horsepower and 360 Nm of torque.

The car pulls slightly to one side, but not as much as it should.
The car now has approximately 125,000 kilometers on the odometer.

The timing belt was replaced at 60,000 km.

'Back then, after the change of staff, I told the friendly employee that the car wasn't cleaning as well as it used to. Apparently, it had been checked, and everything was supposedly okay.'
The timing belt needs to be replaced again, but unfortunately, I still haven't found a competent workshop.

The car's performance varies depending on the situation, but it feels sluggish from around 3,000 to 3,500 RPM. Replacing the mass airflow sensor (MAF) has already made a slight improvement.
This means that the final speed of approximately 200 km/h will eventually be reached.

While I wasn't born with two left hands as a mechanical engineer,
But the difference between theory and practice... when it comes to engine settings, I'd rather not mess with them.

I can definitely see how you might be right, but I also believe that the performance was electronically limited by the engine control unit because there were problems during test runs or in the first production vehicles, which is also evidenced by the 130 hp PD engine.

I think you're on the right track!

I would also be very interested to know how it is with my car.

Is there anyone living in the 67480 area / Southern Westerstraße who might be able to perform a ZR (rotor) change and has a VAg-Com diagnostic tool available, and would be willing to help out?

ttns4 wrote:

The car's performance varies depending on the mood, sometimes with better acceleration, sometimes with worse, especially from around 3,000 to 3,500 RPM, where it feels sluggish. Replacing the mass airflow sensor (MAF) has already helped somewhat. This means that the final speed of approximately 200 kilometers per hour will... eventually be reached.

Hi,

"It's so slow on top, even after the tuning, which really indicates that something is wrong."

The NW (narrowband oxygen sensor) might be misconfigured, but other causes should also be considered - in addition to the MAF (mass airflow sensor), these include insufficient boost pressure, a clogged fuel filter, or a clogged intake manifold due to the EGR (exhaust gas recirculation) system.

My tip: the DIY-control of the NW setting, as described in the technical article, requires the least amount of effort.
For this (at least in my car), no screws need to be loosened; you just need to remove the upper timing belt cover and open the timing mark access port on the transmission.

That's something mechanical engineers should be able to achieve .

'It's so slow on top, even after the tuning, which really indicates that something is wrong.'


'I know a Golf 4 GTI engine from a good friend. With tuning, it produces 140 hp and 408 Nm of torque on the dyno. At 135,000 km, the engine wasn't running smoothly anymore; it turned out to be the mass airflow sensor (MAF) that had failed.'

I hope the timing belt wasn't only replaced at 60,000 km, but also at 120,000 km. Or was the interval mistakenly extended for this particular AJM engine?

@Ulf:

PDs (Pomp Injector Diesel) develop increasingly higher injection pressures as engine speeds increase, reaching up to approximately 2000 bar. This implies that the cylinder filling and, consequently, the combustion process become more efficient. With common rail diesel (CRD) systems, as far as I know, the maximum injection pressure is achieved at lower engine speeds.

The question is whether, with increasing speed, the PDEs or the VEP pump create more resistance in the charging air circuit.
According to your assumption, it should be the PDEs, which would also confirm the reluctance to rotation to some extent.

Julian wrote:

I know the engine from a good friend's Golf 4 GTI. With tuning, it produces 140 hp / 408 Nm on the dyno. The engine also didn't run cleanly at 135,000 km; it was simply the mass airflow sensor (MAF) that failed.

See, this engine also apparently isn't "designed" to have its top end constricted .

Quote:

As engine speeds increase, PDs (positive displacement injectors) develop increasingly higher injection pressures, reaching up to approximately 2000 bar. This implies that the cylinder filling level and, consequently, the combustion process become more efficient. As far as I know, with common rail diesel (CRD) systems, the maximum injection pressure is already achieved at lower engine speeds.

Hm, the higher the injection rate, the greater the "back pressure" before the nozzle, the injection pressure, and consequently, the atomization.
"And the injection rate is directly related to the engine speed for both VP and PD engines -> therefore, I believe the maximum atomization is only achieved in all TDIs at the point where the engine is limited (except for common rail TDIs)."

Quote:

The question is only whether, with increasing speed, the PDEs or the VEP pump create more resistance in the ZR circuit? According to your assumption, it should be the PDEs, which would also confirm the lack of rotational invariance to some extent.

Yes, you can get a rough estimate of the power required for injection just by looking at the "caliber" of the fuel injector.
-> PDs require more power for injection, but also utilize the fuel more efficiently due to finer atomization.
The question is whether, in the end, there will be an increase or decrease in consumption - the practical experience suggests a higher consumption.

Regardless, the desired torque curve can largely be modeled by limiting the injected fuel quantity within a wide range (as long as the turbocharger and the rest of the mechanical components cooperate).

Therefore, I don't believe that the "PD-typical" sluggishness above 3500 rpm is due to a design flaw, because if that were the case, it would occur in all engines (of the same engine code).
But we already have reports for all performance classes, such as "mine works great," and that's even without any tuning.
This, in turn, fuels the suspicion that the reluctant PDs are carrying some kind of flaw or problem with them.
And since replacing the LMM often proved to be ineffective, for me, the next best option remains the NW setting (of course, especially based on my own experience!).

PDs require more power for injection, but they also utilize the fuel more efficiently due to finer atomization.
The question is whether, in the end, there will be an increase or decrease in consumption - the practical experience suggests a higher consumption.


Hmm, not 'my' setup. The PD (likely referring to a specific model or configuration) has a significantly longer gear ratio due to increased power, and on long distances, it typically uses 1.5 liters less per 100km.
In the city, however, it consumes about 1 liter more than my car's fuel consumption.


But we already have reports for all performance classes, such as 'mine works great,' and that's even without any tuning.
This, in turn, fuels the suspicion that the reluctant PDs are carrying some kind of flaw or problem with them.


Hmm, that statement is rather subjective. I've often noticed that the engine's performance suffers under certain weather conditions. However, both the ALH and the AWX engines 'suffer' from this, although the AWX is somewhat less sensitive to temperature.

Julian wrote:

ulf wrote: But we already have reports for all performance classes, such as "mine works great," and that's even without any tuning. This, in turn, fuels the suspicion that the reluctant PDs are carrying some kind of flaw or problem with them. Hm, but the statement is rather subjective to consider? . . .

You're almost spot on with that analogy: What one person might perceive as "a great, powerful lift," another might find "too tight" or "restrictive."

Therefore, in the article about common mistakes, I tried to at least define the "measurement conditions."

a) 3rd gear, full throttle -> just to make sure no one interprets it as sluggish, considering that the last 10 km/h to reach the maximum speed takes "significantly longer" than accelerating 10 km/h in the same gear starting from 2000 rpm.

b) 2. A noticeable loss of power starting around 3500 rpm. Of course, the word "noticeable" is a subjective assessment...

As an objective measurement, one could also log the results of the Dynamic Rotor Balancing (DRB) test and then calculate the actual increase in speed per second from the time-RPM data.

According to simulations under standard conditions, for example, in my car, the first 200 rpm interval should take 0.56 seconds, and the last one 0.85 seconds.
The key factor here is the ratio of the times: 0.85 / 0.56 = 1.52.

If a log reveals that the maximum acceleration at 2000 rpm is twice as strong (instead of 1.52 times) as it is at 4000 rpm, it appears that the torque drops off relatively significantly at higher speeds.
With my car, the upper timing chain cover would then detach on its own.

It's quite difficult to explain such a calculation for a real log file... if anyone has a simpler way, please share it!

Hello,

da Hopa immer noch offline ist, hier ein Auszug aus dem o.a. Test report:

Quote:

. . . According to the Hopa dynamometer test, our test vehicle only has 121 horsepower instead of 130. Additionally, the torque drops at 3400 rpm.

With the Hopa-Box installed, the engine was measured to produce 156 horsepower at 3900 rpm and 360 Nm of torque at 2000 rpm.

Assuming that the Hopa measurement of the standard engine is reasonably accurate, the result, in my opinion, corresponds quite closely to the relevant reports stating that "it starts to fail above 3500 RPM" . . .

OK, it's theoretically possible that the problem is related to the mass airflow sensor (MAF). However, Hopa had (and has) its own (quite useful) information on its website, so one can assume that they wouldn't send a car with a faulty MAF sensor for testing...

The history of NW (presumably referring to a specific technology or component) seems to have been relatively unknown (at least until recently; the cited test is already quite old); therefore, it seems quite plausible that a motor with an incorrectly adjusted NW setting could have been present in the test.

'It's so slow at the top, even after the tuning, which really indicates that something is wrong.'


'I know a Golf 4 GTI engine from a good friend. With tuning, it produces 140 hp and 408 Nm of torque on the dyno. At 135,000 km, the engine wasn't running smoothly anymore; it turned out to be the mass airflow sensor (MAF) that had failed.'

I hope the timing belt wasn't only replaced at 60,000 km, but also at 120,000 km. Or was the interval mistakenly extended for this particular AJM engine?

@Ulf:

PDs (Pomp Injector Diesel) develop increasingly higher injection pressures as engine speeds increase, reaching up to approximately 2000 bar. This implies that the cylinder filling and, consequently, the combustion process become more efficient. With common rail diesel (CRD) systems, as far as I know, the maximum injection pressure is achieved at lower engine speeds.

The question is whether, with increasing speed, the PDEs or the VEP pump create more resistance in the charging air circuit.
According to your assumption, it should be the PDEs, which would also confirm the lack of rotational invariance to some extent.

@Julian & Ulf:
The LMM (likely referring to a mass airflow sensor) was recently replaced, about 2000 km ago, and the engine runs better now, but not 'perfectly well.'
The AGR valve was replaced about 1.5 years ago and hasn't really done much since then.

This Saturday, I had some luck; I managed to convince a mechanic to come by and check my car using a VAG-Com diagnostic tool, but he wasn't able to figure it out.
I managed to get it to a point where I could log in myself.

I logged into engines Login 01 & 03, and minimized the AGR (Abgasrückführung - exhaust gas recirculation) rate in channel 03.
brought improvements in smoother acceleration & fuel consumption despite a faulty AGR!

The fuel injection amount for channel 01 could not be moved by the slider, perhaps it has something to do with the OBD tuning data that was loaded, so that nothing is overwritten??

That's it then.

@Julian You've understood correctly: The timing belt replacement is officially overdue.
there is / there are
1. No money (completely broke because of all the troubleshooting).
2. Conflicting statements (service intervals of 60,000 to 90,000 km! from VAG workshops and VAG dealerships!).
'Recently, there have been a surprisingly large number of defects occurring (after the necessary replacements), such as problems with the tension rollers leading to screw defects and timing belt tears. I'm wondering if this is due to the newer replacement parts or if it's a problem with the workshops.'
4. I believe that my timing belt is not under extreme stress due to the lack of power.
But I wanted to solve the existing problem beforehand!

I'm just hoping for luck and chance.

I still believe that the problem is likely an electrical issue with the control data (or control unit) or some faulty sensor that is causing a significant lack of power.

(By the way: Biodiesel is being excluded [from use], and I think the car runs better in the morning when it's cold.)
I certainly don't want to confuse you, I just wanted to share my impression.

Hello.
Thorsten.

My engine's idle speed is actually quite stable, even above 3500 RPM. Subjectively, around 3000 RPM seems to provide the best acceleration when driving uphill on the highway.

I drove a ********-ATD (@96kW) and it had a very noticeable drop in power at 3500 RPM, which was also confirmed by a comparison test.

130-160 (4th): 9 to 12 seconds.
160-180 (5th): 7 to 12 seconds.

Both tests require engine speeds well above 3000 RPM. While the chipped version has slightly slower acceleration (though it's running on 215/40 tires instead of 185/60), the speedometer indicates it's almost 5 km/h faster in terms of top speed. My ATD is currently running with a faulty EGR valve and a coolant temperature sensor in the diesel line.

The fuel injection amount for channel 01 could not be moved by the slider, perhaps it has something to do with the OBD tuning data that was loaded, so that nothing is overwritten??



'That's not possible with a PD engine because it doesn't have a conventional fuel injection pump.'

CU Gremlin.

Gremlin wrote:

ttns4 wrote: The fuel injection amount for channel 01 could not be moved by the slider, perhaps it has something to do with the OBD tuning data that was loaded, so that nothing is overwritten?? That's not possible in a PD (presumably referring to a specific type of engine or system), because it doesn't have an injection pump in the conventional sense

.
Hi Ralf,

Why is the channel "apparently adaptable" ?

Just like the channel with the start of the feed (4?): While entering other numbers is not blocked, after pressing the return key (to save), the default value reappears .

If I knew that...

Perhaps something similar to the plateau function in the Kombi, to avoid confusing poor Klingons!?

CU Gremlin.

The fuel injection amount for channel 01 could not be moved by the slider, perhaps it has something to do with the OBD tuning data that was loaded, so that nothing is overwritten??
That's not possible in a PD (presumably referring to a specific type of engine or system), because it doesn't have an injection pump in the conventional sense .
Hi Ralf,

Why is the channel 'apparently adaptable' ?

Just like the channel with the start of the feed (4?): While entering other numbers is not blocked, after pressing the return key (to save), the default value reappears .

@Ulf @Ralf

Are you sure that it is not possible to adapt channel 01 for all PDs?
I've definitely read this before, I think it was also in the Passat 3B forum.

Of course, it's also possible that I misunderstood, or that I read between the lines.

By the way, I had another thought, which might be a bit far-fetched, regarding the loss of performance:
How exactly can a helpful person check the diesel temperature sensor in the fuel line?

I once had a power box installed for testing purposes. The car definitely had a lot more power, but the engine sounded a bit unhealthy, which is why I then opted for OBD tuning.

Question:
To what extent can the processing of this signal be 'configured' within the control unit?

That would be an alternative and, in my opinion, would simply explain the concept of series scatter.
As I said, it's just an idea.

Regards,
Thorsten.

ttns4 wrote:

Are you sure that it is not possible to adapt channel 01 for all PDs? I've definitely read this before, I think it was also in the Passat 3B forum. Of course, it's also possible that it wasn't true, or that I read between the lines.

Hi Thorsten,

I haven't tried the first one yet.

Quote:

How exactly can a friendly person check the diesel temperature sensor in the fuel line?

I would say, within the scope of the diagnostic comparison, we're looking at water, air, and diesel, with the engine cooled down.
I don't know if he still has tolerance curves, for example, for measurements taken in a water bath.

Quote:

To what extent can the processing of this signal be "configured" within the control unit?

The standard way, as far as I know, doesn't allow that at all.
Abnormal pathways are described in detail in the m 10c articles.

Quote:

That would be an alternative & would, in my opinion, simply explain serial scatter. As I said, it's just an idea.

The diesel temperature is not evaluated in a "speed-dependent" manner. If there's a problem, it will occur across the entire speed range, not just above approximately 3500 rpm.

@all:

After disconnecting the battery, the 'addition values' in the control unit seem to...
to be deleted. However, these values are reset automatically after a certain amount of driving time, based on driving style and other parameters, regardless of whether or not OBD tuning has been applied.

I also noticed this issue with our Passat when it had a loss of power. Since the tuning, it's not as pronounced anymore, but it's still present.

Here are the questions I have for this species:

A)
Can the addition values be blocked in any way (in some cases, I believe they are unintentional )?

B)
After disconnecting the battery, the car behaves very aggressively (the wheels immediately spin if you don't start very carefully). For example, there was extreme acceleration after installing the new control unit after the OBD tuning, and the battery was disconnected at that time.

So far, no workshop has addressed this point.

Now, the question is whether there might also be a difference between OBD tuning and a new chip.
It's just a guess.

Perhaps someone knows more about this subject.

Regards,
ttns4

ttns4 wrote:

After the famous battery disconnection, the "addition values" in the control unit seem to be erased. These are then reset after a certain driving time, based on the driving style and other parameters, regardless of whether it is OBD tuning or not.

That would be the first thing I've heard about TDIs.

According to the SLP (Service Life Protocol), my vehicle's PD (presumably a component or system) does not have a permanent power connection to the engine control unit (ECU), and therefore cannot detect when the battery is disconnected. It can only detect when the ignition is turned on or off.

If every time you turn the ignition off and on, it would erase the adaptation values, that would not be in line with the original design intent.
I haven't observed anything like that before, nor have I noticed any more aggressive acceleration after each engine shutdown or battery disconnection.

I can't rule out the possibility that it might look different in other TDIs, but I would be surprised.