Is injection duration critical for PD tuning?

Hello everyone,

The May 2003 issue of "Autotuning" magazine features descriptions of two Polos (base models with 100 horsepower).
According to the article, MTM achieves only 130 hp / 310 Nm with chip tuning alone. Wendland, with a larger turbocharger and intercooler plus chip tuning, achieves 170 hp / 380 Nm – but apparently, these are just manufacturer's figures, as there are no dyno test results or similar documentation available.

What's surprising is that even for the supposed 170 horsepower, the PD (direct injection) components of the 100 horsepower engine are still sufficient, because there's no mention of changing the injectors anywhere (unfortunately, I couldn't find any information about this modification on the Wendland website).

I can only explain this by assuming a significantly higher injection rate (in mg/crank angle) for the PD process compared to the VP process, because with the VP process, it would likely not be possible to achieve at least 70% more injection volume without hardware modifications or piston melting.

On the other hand, B+B offers an upgrade of the 100 HP PD to "only" 150 HP / 340 Nm, including a "special" turbocharger and "special" injectors.

Does anyone here know more about this topic?

Hi Ulf!

Here's my two cents on that:

The question is, how far does the material get affected? To the best of my knowledge, the PDs (presumably referring to a specific type of engine component) do not differ from the VEPs (another type of engine component) in terms of hardware, such as displacement, bore, stroke, etc. Furthermore, the insertion depth of the injector bodies into the cylinder head is the same for both.

In my opinion, this would mean that extending the injection duration in both cases would result in the same problems with diesel fuel wetting the piston surface.

Another question I have is whether the throughput of PDs is actually lower than that of VEPs. What do you mean?
I believe that a significant increase in boost pressure is achieved here. To get a PD_130 engine to produce approximately 165 horsepower and around 420 Nm of torque, tuners typically use a boost pressure of about 2 bar. The original pressure is around 1.3 bar, which is a lot.

The values determined by certain tuners can be displayed using VAG-COM. This shows what the engine control unit (ECU) calculates as the engine's theoretical power output based on the engine settings. Whether this can ever be achieved in practice is questionable, as a wet piston is unlikely to last very long.

...

Hello Julian,

Quote:

To "tune" a PD_130 engine to produce approximately 165 horsepower and around 420 Nm of torque, tuners typically use a boost pressure of about 2 bar. The original is at about 1.3 bar.

That's quite a lot.
Are you sure? The 150 horsepower PD engine only has a boost pressure of 1.5 bar.

Best regards, Rainer.

Okay, here's the information about my tuner, WKR. And the PD_150 only has 'just' 320 Nm of torque.

Julian wrote:

In my opinion, this would mean that when extending the injection duration in both cases, the same problems with diesel wetting of the piston surface would be encountered.

Hi Julian,

so must not be the case, in my opinion.
Let's assume a VP-TDI distributes the full load injection over 30° of crank angle, while a PD injector, for example, distributes it over 20° of crank angle (the numbers are arbitrarily chosen).
This would initially mean a more demanding course for the PD participants, but they are known for handling such challenges.

Furthermore, in the PD system, the injection duration, and thus the amount, could be increased by approximately 50% before reaching the normal injection duration of the VP engine.

Let's assume, for the sake of argument, that piston melting begins with an injection duration of 45°kW.
Then, with a VP-TDI engine, you could achieve a maximum fuel quantity increase of 50% (excluding advanced injection timing), while with a PD engine, it's 125%... Do you understand what I'm getting at?

Hi Ulf!

Yes, I understand that, I probably thought too much about it.

I'm not very good with data, but what's currently striking me as a significant difference between the ALH (90 hp) and the AWX (130 hp) models is:
I've driven both engines, the ALH in a Golf 4 and now the AWX in an A4.

In a direct comparison, I've noticed that the PD (presumably referring to an engine or component) is much more responsive in terms of revving. Above 3000 RPM, it starts to build power significantly, and by 4200 RPM, it barely lets up.
An older ALH model, however, starts to noticeably reduce the VEP pump's performance from around 4000 RPM.

The fuel consumption is noticeably lower than in the Golf, despite the 40 extra horsepower.

My assumption is that the PDs (presumably referring to pre-combustion chambers or similar) atomize the fuel much more finely, which makes it 'harder' for the piston to reach the bottom of its stroke. Therefore, it's easier to increase the boost pressure and thus the diesel-air mixture without jeopardizing the engine components. Generally, it is observed that more power can be extracted from PD devices compared to VEP devices.

So... I hope I didn't think of something too stupid...

Hello Ulf,

Quote:

I can only explain this by assuming a significantly higher injection rate (in mg/crank angle) of the PD process compared to the VPs, because...

I see it the same way. I found the following information about the PD elements in my documents:

The fuel injection volumes in passenger cars vary between 1 mm³ (pre-injection) and 50 mm³ (full load injection). This amount is expelled through an opening of less than 0.25 mm² within 1 to 2 milliseconds.

If you knew the injection angle range used in a VE-TDI system, we could compare the injection rates.

Here's a small example to illustrate the concept:
At a speed of n=4000 RPM, the motor requires 15 milliseconds for one revolution, which corresponds to 360° of the kilowatt-hour (KW).
In 2 milliseconds, therefore, 2/15 * 360 = 48 degrees of the KW scale are covered.

How about the VE-TDIs?

Regards,
Alex.

donalexo wrote:

At a speed of n=4000 RPM, the motor requires 15 milliseconds for one revolution, which corresponds to 360° of the kilowatt-hour (KW). In 2 milliseconds, therefore, 2/15 * 360 = 48 degrees of the KW scale are covered. What about the VE-TDIs?

Hi Alex,

According to an MTZ article, the Pmax injection duration for the 1Z engine is 36° KW.

The 1 to 2 ms mentioned by you for PDs unfortunately include an uncertainty of 50% .
I think this involves the "speed issue," meaning the injection duration at 4000 rpm is approximately 1 millisecond, which corresponds to 24 degrees of crankshaft rotation.
This would explain why PDs (presumably a type of device) have a significantly higher reserve for injection duration compared to VPs (presumably another type of device).

Hi Ulf,

Quote:

The 1 to 2 ms you mentioned for PDs unfortunately include an uncertainty of 50%. I believe that "the dwell angle issue" is involved, meaning that the injection duration at 4000 rpm is approximately 1 millisecond, which corresponds to 24 degrees of crankshaft rotation. That would explain a significantly higher injection time reserve for PDs compared to VPs.

I'm not entirely sure about that. The injection time for the PDs depends on both the speed and the amount. For the full load capacity, the solenoid valve must logically remain energized for a longer duration (in terms of a larger kilowatt interval) than it does at partial load or idle.
However, I also think that the 2ms injection time is likely achieved under full load at low engine speeds, because that's when the full amount of fuel needs to be injected into the cylinder.
At least, the correlations observed in PD suggest a certain degree of reserve in injection duration.

Regards,
Alex.

donalexo wrote:

For the full load quantity, the solenoid valve must logically engage for a longer duration (in terms of a larger kilowatt interval) than it does at partial load or idle. I also think that the 2ms is probably achieved more often at full load in the low RPM range, because that's when the full amount of fuel needs to be injected into the cylinder.

Hi Alex,

Okay, so we agree that the full-load injection duration at 4000 rpm is "a bit shorter" for PD engines than for VP-TDIs.
Why do you then start your post with...

Quote:

I'm not entirely sure about that.

Hi Ulf,

This is because at higher speeds, another effect comes into play. In positive displacement systems, the maximum pressure achieved is highly dependent on the speed. This means that at high speeds, leakage increases. These need to be compensated for by extending the activation time of the solenoid valve.
Generally, the required kilowatt interval for PDs also increases again with the speed.
Unfortunately, I cannot precisely determine the injection duration that would result from that at full load and rated speed. I am missing the technical details for that.

That's why I started my post in such a measured and cautious way.

Regards,
Alex.

ulf wrote:

What's surprising is that even for the supposed 170 horsepower, the PD (direct injection) components of the 100 horsepower engine are still sufficient, because there's no mention of changing the injectors anywhere (unfortunately, I couldn't find any information about this modification on the Wendland website).

I've had the same thoughts myself.
The initial inspiration came from a Skoda Fabia PD with 101 horsepower, which ******** had modified solely through chip tuning.
it was allegedly increased to 169 horsepower, which would represent a power increase of approximately 68%.
Such performance improvements were only achievable in VP TDI engines by replacing the injectors.
IMHO, the PD injection pressure of up to 2,200 bar was used to position the injection volume around the optimal injection timing. The finer atomization is achieved anyway by the higher pressure. This suggests that the nozzle throat diameter remained relatively constant in relation to the pressure of the VP TDI.

As mentioned before, in the VP TDI engines, the injectors were the throttling unit.
Since the maximum power is achieved at high engine speeds, typically around 4,000 RPM in a TDI engine, using smaller injectors results in insufficient time to optimally deliver the fuel injection amount.
This disadvantage is compensated for in PD systems by the injection pressure.
"This allows you to fully exploit the engine's potential."
Piston seizure can be almost completely ruled out in direct injection engines by ensuring the fuel injector spray hits the piston.

These are at least my thought processes.
but it's all just theory, after all.
I assume no liability for engine damage or states of confusion *g*.

Hi.

...while I absolutely cannot understand the "essential higher idle speed" with the 216 injectors, based on my experience (without additional chip tuning).
I currently consider this to be nothing more than a placebo ingredient, used to make the product seem more complex to customers than it actually is - perhaps to deter potential "discount shoppers" .

If anyone here knows what deeper thoughts Mr. ***** had behind this, I would be curious to learn them .

My speech.

This paragraph seemed suspicious to me from the very beginning.
Finally, the idle speed is electronically controlled and...
As far as I know, the injection quantity can be adjusted continuously down to a value of 0.

*digging up an old thread*

Hello again,

After comparing VP (voltage protection) and PD (partial discharge) target data, and an MTZ (German electrical engineering journal) article, I have determined the following injection times for angle measurement in the full load range.

-> The 1Z (90 hp) engine injects fuel for approximately 36 weeks.
-> ATD and AXR (100 hp) engines inject fuel for approximately 24 weeks.
-> ASZ and AWX (130 hp) engines inject fuel for approximately 28° crank angle.

Unfortunately, the 36° KW value for the 1Z likely refers to the Pmax point at 4000 rpm, while the PD data applies to approximately 3000 rpm, and presumably, the PD angle would also be a few degrees larger at 4000 rpm.

A possible response could be a VAGCOM log of block 4, for example, a DZR test. Does anyone happen to have something like that ready?

For now, however, considering the significant differences mentioned above, It's worth noting that with PD tuning, the injection duration can be extended with less risk (in terms of piston melting), and initially, it can also produce less soot compared to VP-TDI.

ulf wrote:

Hello everyone, The May 2003 issue of "Autotuning" magazine features descriptions of two Polos (base models with 100 horsepower). According to the article, MTM achieves only 130 hp / 310 Nm with chip tuning alone, while Wendland, with a larger turbocharger and intercooler + chip tuning, achieves 170 hp / 380 Nm.

However, apparently, these are all just manufacturer's specifications, as there are no dyno test results or similar documents available.

Hello!

The Wendland Polo was a 74kW TDI. However, the brothers swapped the 96kW TDI engine into the smaller Polo. It also came with a 6-speed gearbox. Then she tuned it up to 170 horsepower.


Regards,

Raoul.