Boost Issues: Low RPM, 100-130 HP PD Engines

Hello,

According to various reports, the 100 hp PD models start noticeably better at low RPMs compared to the 130 hp models. The often-cited explanation is the larger turbocharger in the 130 hp models, which needs to deliver more boost at higher RPMs and therefore runs slower at lower RPMs.

For clarification, I checked my LDA while driving uphill at full throttle in the highest gear.
0.5 bar at approximately 1200 rpm.
1.0 bar from approximately 1500 rpm.
The pressure remains at 1.0 bar initially (meaning the control system intervenes here, presumably to prevent the turbocharger from operating in the pumping range), and only above approximately 2000 rpm does the maximum value of 1.3 bar become active.

Overall, the ASZ engine builds up the same or more boost pressure compared to, for example, the AFN engine. However, the AFN engine still produces more torque, which is noticeably more directly related to the boost pressure than in the case of the ASZ.
According to this, the weakness of the turbocharger at low RPM is apparently not due to a lack of actual air, but rather to a harsh torque and/or power limitation.

The smaller turbocharger of the ATD/AXR will, in my opinion, behave more like the (also smaller) one of the AFN at the lower end of the RPM range, so the 100 HP engines probably won't have a boost pressure advantage in the low RPM range (-> ATD and AXR owners with LDA or corresponding data logs: please respond ).

For me, the better acceleration of the 100 hp engines is (initially) only the result of a software tuning that is "more similar to a VP" (presumably referring to a specific tuning style or brand).

But why is this relative sag programmed into the ASZ, as it represents a significant disadvantage in everyday use?
Does one want to portray the ASZ as particularly comfortable, considering that it doesn't even produce noticeable vibrations when accelerating from idle speed?
Or could it be due to the larger particulate matter (PM) that, (speculation on) when operating at low RPM, doesn't atomize as well (speculation off), resulting in the ASZ ultimately only being soot-suppressed?

A modified version of the dynamic resonance zone (DRZ) within the range of 1500-2500 RPM, when compared to the "actual" DRZ, might be helpful.

bloeckler wrote:

A modified DZR (Dynamic Resonance Frequency) in the range of 1500-2500 RPM, when compared to the "actual" DZR, might be helpful.

Hi,

"In my opinion, there are too many uncertainties involved, for example, if one charger ramps up slightly slower than another, it could potentially lead to a loss of torque and distort the comparison. However, from 2000 rpm onwards, every (functional) charger should be operating within a controlled range, which should enable more reproducible results."

Today, I performed a data logging of the torque limits: 5th gear, full throttle, going uphill, from 1000 to 2300 rpm. Due to the very slow increase in engine speed (total duration 33 seconds), I essentially obtained the "static" engine operating data.

It is noteworthy how closely soot reduction and torque limitation are linked.
Between 1000 and 2000 rpm, there was, on average, only enough air available for an additional 0.3 mg of fuel injection.
The maximum allowable excess air would have permitted 4.6 mg more fuel injection for a single second, while the most severe air shortage reduced the fuel injection amount by 2.7 mg, but already at 1134 rpm.

Here are the actual mg/hub injection amounts (i.e., the lowest limit) in 100 RPM increments:
1000 -> 30
1100 -> 33
1200 -> 37
1300 -> 41
1400 -> 45
1500 -> 47
1600 -> 50
1700 -> 52
1800 -> 55
1900 -> 56
2000 -> 55
2100 -> 54
2200 -> 54
2300 -> 53.

It would be interesting to compare this with an ATD/AXR to determine whether their (subjectively) better low-end torque is a result of more fuel injection, shorter rpm-to-km/h ratios, or a lower subsequent Nm peak.

"The efficiencies of both engines are likely to be largely identical (bore, stroke, and camshaft are the same), so you can practically directly infer the torque based on the fuel injection amounts - or am I mistaken?"

Well, since no data came from the ATD/AXR, I calculated a torque comparison based on the logged injection quantities from the ALH and ASZ engines.

Even the "weaker" ALH engine exhibits the typical VP characteristics in its low-rpm range, and it performs more powerfully than the ASZ engine, especially when going uphill. In such situations, you often have to shift the ASZ engine down a gear to prevent it from losing power.

Based on the injection quantities, the ASZ offers a performance advantage at every engine speed. . . can someone explain that?

EDIT:
While correcting some minor errors in the diagram, I also included the AFN (presumably referring to a specific element or feature).
It's clear from the curve that the one with the ASZ engine is superior, as the shorter gear ratio in the Golf 3 and the weight advantage contribute to this.

ulf wrote:

... Based on the injection quantities, the ASZ system has a clear advantage at every engine speed... can someone explain this?

Longer gear ratio?

joegolf wrote:

ulf wrote: ... Based on the injection quantities, the ASZ system has a clear advantage at every engine speed... can someone explain that? Longer gear ratio??

Well, in the higher gears, the Polo typically has a gear ratio that results in approximately 9% higher speed per engine revolution (rpm -> km/h). Additionally, there's an extra weight of about 80 kg, which is roughly a 7% increase (when driven solo).

Combined, these factors initially reduce acceleration by approximately 16% - which is exactly the amount of extra torque the ASZ produces at 1000 rpm.

So, theoretically, at 1000 rpm, they should be equal, and above that, the Polo should pull ahead of the Ibiza because its Nm advantage increases with engine speed.

According to the Popometer, the ASZ engine doesn't surpass the ALH engine in power until around 1400-1500 rpm.

According to various reports, the 100 HP PD models start significantly better at low RPMs compared to the 130 HP models.

Hmm, if the ALH already has a VTN17 (like in the movie 'Gremlins 2: The New Batch!'), then the PD_100 probably has one too, right? And the VTN17 in the PD_130 hasn't been significantly (or at all) modified, has it?

Regarding the boost pressure on my AWX, I understand what you're saying, although the pressure builds up faster in my case. I'm already reaching 1.3 bar at 1600 RPM.
My engine reaches its maximum torque at 1750-1950 RPM, but yours, the ASZ, only reaches it at 1900 RPM, right?

Julian wrote:

Hmm, if the ALH already has a VTN17 (see Gremlins 2: The New Batch!), then the PD_100 probably has one too, right?

The turbocharger in our Ibiza is a few millimeters larger on the outside than the one in the AFN Golf 3. It's probably already the VNT17 turbo.

Quote:

Regarding the boost pressure on my AWX, I understand your information, although in my case, the pressure level increases more quickly.

At 1600 rpm, I have 1.3 bar of pressure.

Quote:

Interesting... In my case, it's very clear that this regulation will initially put a stop to things, at least until it reaches a threshold of 1500.

My engine also reaches its maximum torque at 1750 RPM - 1950 RPM, while yours, the ASZ, only reaches it at 1900 RPM or higher, right? }
Okay.

My engine also reaches its maximum torque at 1750 RPM - 1950 RPM, while yours, the ASZ, only reaches it at 1900 RPM or higher, right?
Correct.

Interestingly, my engine (AWX) achieves the above figures with a 5-speed gearbox, while the identical engine (AVF) with a 6-speed gearbox produces 310 Nm of torque at only 1900 rpm. My engine has a torque plateau, while the AVF engine has a peak torque value.
It was also interesting to note that both engines reached a maximum of 330 Nm on the vagcom, but the AWX reached it slightly earlier. The catalog promised 285 to 310 Nm. *pondering*