PD Motor Problems: Common Failure?

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 the group think about my theory?

I can also imagine that the PD engines are leaned out in the higher RPM range, so that the turbo's VTG (Variable Turbine Geometry) can still regulate precisely and doesn't overshoot. This is currently the case with my tuned VP-TDI engines.

The exhaust gas flow is increased at higher engine speeds to ensure that the variable turbine geometry (VTG) operates at its maximum setting, while still allowing the boost pressure to increase.
A larger turbocharger would help, for example, a VNT 20.
This has the disadvantage that it doesn't fully engage until around 2000 RPM.
That is my theory and information.

I hope it came across the way I intended.

Conclusion:
The manufacturers maintain a significant safety margin to account for these unintended consequences of the turbocharger.


Can anyone else agree with that opinion?

@ulf

Okay, I can't understand how the 85 kW PD (AJT) engine is supposed to have a 35% power reduction. I actually think it's more responsive than our old 1Z engine. The ATJ engine revs willingly up to 4,500 RPM (in 4th gear) before the power drops off, which the 1Z didn't do, even though it could also rev above 4,000 RPM (unfortunately, not in the highest gear, and the ATJ can't either). I don't really notice any difference compared to the old VP engine, except for the fuel consumption, which is unfortunately higher in the new Passat.

However, our ATJ already had its timing belt replaced.

Best regards, WarLord.

WarLord wrote:

So, I can't understand that the 85 kW PD (AJT) is supposed to drop by 35%. I even think it's more responsive than our beloved 1Z. The ATJ revs willingly up to 4,500 RPM (in 4th gear), and then it drops, which the 1Z didn't do...

Hi,

Then, it could be assumed that the northwest setting is correct for your AJT.

Looking at the torque curves in the driving data sheet (and the "Nm levels" between the engine speeds in the 200 rpm grid), one notices that the power delivery decreases almost linearly between 2000 and 4000 rpm. In particular, there is no "sharp drop" in torque to be observed between 3000 and 4000 rpm, which, however, should be the case according to the common complaints.
In contrast, the 110 hp version maintains the Nm value above 2000 for a longer period, remaining relatively constant, before dropping off more noticeably above 3000 rpm.

Based on this data, in practice, the 110 series VPs should exhibit the characteristics that are often attributed to the PDs.

These considerations, your experience with the AJT (does it also have 310 Nm?), and not least my engine, confirm my suspicion that the "nothing more comes after 3500 rpm" wisdom might be based on (massively) incorrectly calibrated PD injectors.

Steffarn wrote:

I can also imagine that the Pd. engines are leaned out in the upper RPM range, so that the Vtg of the turbo can still regulate precisely and doesn't overshoot.

Hi,

That would only be a problem, in my opinion, if it were constructively impossible to further expand the adjustment range of the VTG (Variable Turbine Geometry) in the full load range to allow for more "bypass" (i.e., around the drive turbine).
(Because that would also solve your problem.)

But I can't quite imagine that it shouldn't be possible...

Then, it could be assumed that the northwest setting is correct for your AJT.

Looking at the torque curves in the driving data sheet (and the 'Nm levels' between the engine speeds in the 200 rpm grid), one notices that the power delivery decreases almost linearly between 2000 and 4000 rpm. In particular, there is no 'sharp drop' in torque to be observed between 3000 and 4000 rpm, which, however, should be the case according to the common complaints.
In contrast, the 110 hp version maintains the Nm value above 2000 for a longer period, remaining relatively constant, before dropping off more noticeably above 3000 rpm.

Based on this data, in practice, the 110 series VPs should exhibit the characteristics that are often attributed to the PDs.

These considerations, your experience with the AJT (does it also have 310 Nm?), and not least my engine, confirm my suspicion that the 'nothing more comes after 3500' wisdom might be based on (massively) incorrectly adjusted PD-NW settings.

It's not AJT, it's ATJ. It's the 85 kW PD engine with 310 Nm of torque, which was designed for the 6-speed gearbox.

I suspect it might be the camshaft timing. The car has already had a timing belt replacement (it was bought after that), and I was actually surprised that it rotates that far. We have a few brand new Tourans at work (okay, they already have 25,000 km), which are freshly broken in, and there's absolutely nothing above 4,000 RPM, but it works normally (subjectively) up to 4,000 RPM. However, what I noticed with the ATJ is that the torque seems to be regulated in stages up to 3,000 RPM (but I'm attributing that to the leaky intercooler). Let's see how it is with the new intercooler.

Best regards, WarLord.

My AJM (85kW) definitely revs better after the timing belt replacement.

I also already have a large turbocharger and other related parts, but I'm hesitant to try it because I'm going to school for the next two years, and I can't afford to have the engine fail.

DaBibo wrote:

My AJM (85kW) definitely revs better after the timing belt replacement.

Hmm, it could also be due to an elongation of the timing chain, which would naturally shift the NW setting even later (but how much difference that makes -> ???).

Or perhaps your ignition timing was incorrectly set from the factory, and it was only adjusted correctly during the spark plug replacement.

Did you change it yourself?
If not, then just the (presumably) correct ZR setting alone would be worth a "secret tip" point for your workshop.

DaBibo wrote:

My AJM (85kW) definitely revs better after the timing belt replacement.

Hi,
If Ulf's theory is correct, then we should observe this effect on a large scale, provided that the work is done professionally.[/img]

christians wrote:

If Ulf's theory is correct, we should observe this effect on a large scale, assuming proper workmanship

.
And that's precisely where things are likely to fail - at least for "ordinary" workshops.

Or, perhaps, more PD drivers should check their NW settings themselves.
It's not actually that difficult - and you might get arguments that you can occasionally bring up in a discussion with VAG or a workshop.

We were chasing the ASZ today...

It revs up smoothly to the redline without feeling constricted.

CU Gremlin.

@ Ulf,

I already wrote about this in a thread about Gremlins. Today, following your instructions, I finally dared to adjust my timing (1. timing belt, 40,000 km). And sure enough, the deviation was so minimal that I almost didn't want to loosen the crankshaft pulley. I think it was just under a degree, maybe a maximum of 2°. If I'm correctly informed, I'm the third or fourth person to have tried this (and found the time to do it). It's really quite doable, and Ulf's instructions get to the point. I used that blue sealant from Loctite on the crankshaft pulley side and also on the opposite side. I would recommend this to everyone, because even in the good old KTM days, the LC4 engines were made 100% leak-proof; which is anything but self-evident.

I drive a Fabia TDI ATD with 101 horsepower and 240 Nm of torque. Last year, the car could still reach up to 4300 RPM in 5th gear, which corresponds to 220 km/h according to the speedometer. However, I don't want to start a discussion about the maximum speed, but rather about the revving ability that I have personally confirmed.

'Yesterday, my car's turbocharger (ATD) only reached 4000 RPM, even though nothing has been changed on the car (same wheel width, etc.). I even got a new mass airflow sensor (MAF) completely free of charge during the winter. Could it possibly be related to this adjustment, or is it simply an old air filter (I now have 56,000 km on the odometer and still have the old air filter).'

How can I, as someone with limited experience, check this 'NW Rad' (please explain what that is) without using electronic tools? Is it even possible? I have a technical background in mechanical engineering, so I'm not completely clueless about these things, but I'm still a beginner when it comes to engines.

best regards

Jack

Hi Ulf!

One must keep in mind:

A PD engine delivers a pronounced 'torque peak,' while a VEP engine doesn't quite achieve the same. In my ALH engine, the power output noticeably dropped above 3800 RPM (no surprise, as 66 kW was reached at 3750 RPM). After the tuning, it improved somewhat. However, it then pulled cleanly from 1200 RPM onwards, whereas before 1600 RPM, it felt very sluggish.

The AWX engine revs freely all the way into the red zone, whether it's new or slightly broken in. Subjectively, however, you get the feeling that after that brutal peak torque at around 1900 RPM, not much more comes. But if you compare it to other vehicles on the highway, you notice that it accelerates quite quickly. Drivers of 320d models are always complaining behind me, but this engine already has excellent pulling power.

Of all the TDIs I've driven, the most eager to rev was the 1.4 PD_TDI in the A2... a big compliment regarding its sound, fuel consumption, and performance!

We were chasing the ASZ a little bit today...


Again, sometimes.

Best regards, WarLord.

Jackrabbit82 wrote:

Yesterday, my ATD (turbocharger) only reached 4000 RPM, even though nothing has been changed on the car (same tire width, etc.). I even got a new MAF sensor (mass airflow sensor) with 100% warranty coverage during the winter. Could it possibly be related to this adjustment, or is it simply an old air filter (I now have 56000 km on the odometer and the old air filter is still in place).

Hi,

Please, just check the oil filter .
There are many possible causes for a loss of performance.
Starting with issues from the factory (even new cars can have defects, everything has already been used), to clogged fuel filters, turbocharger problems, and so on, all the way to pure imagination:
A tailwind or headwind of 5 km/h is hardly noticeable, but at maximum speed, it can make a difference of as much as 10 km/h!

Quote:

How can I, as a "talented borrower," check this "NW wheel" (please explain to me briefly what that is) without electronic aids?

Camshaft gear.
Click here. If you don't understand this after careful reading, it's best to leave it alone (don't take it personally , just for the safety of your own well-being).


@Julian:

Quote:

A PD delivers a pronounced "torque peak," while a VEP does not quite as much.

Yes. Nevertheless, the torque curve drops off relatively evenly at higher RPMs (in Nm of loss per 100 rpm).
However, according to reliable reports, the torque drops "abruptly" around 3500 rpm, which means that the loss of Nm per 100 rpm should become significantly larger from that point onwards.

However, at least with the more rev-happy PD engines, such a "dip" is not noticeable. Therefore, I believe that a significant loss of power below 4000 rpm indicates a defect or incorrect setting.

Quote:

Of all the TDIs I've driven, the 1.4 PD_TDI in the A2 was the most eager to rev.

I once drove a Polo from the latest generation with the 1.4-liter engine (75 hp), but it had 3 people in it. At speeds below ~1700 rpm, it barely had any power.

And because of the larger spark gap, 4000 rpm sounds like 3000 rpm in "normal" engines -> the gear is ending, even though the ear, due to habit, signals "pull it up further."
Well, this idea hasn't really convinced me...