Warum sind PDs obenraus so "lahm"? | Posts 32+

So, I was just talking to a colleague who drives an Octavia with an ASZ engine...
. . . untuned


Sure. Company cars (fleet vehicles). Everything that costs money is bad. And tuning costs money, so it's HIS money. That's why he drives an Octavia, with everything the equipment list offers (navigation, etc.). He would only have gotten a V6 TDI Passat as a basic model. But then there's really NOTHING included, and it still costs more money.


That sounds plausible... but still, he seems to be in the minority with that viewpoint (for whatever reason).


So far, he has only complained about how long it takes for the car to warm up.
(He drives the first 10 kilometers, but mostly downhill, which is why my ALH engine also has an average fuel consumption of 2.4 liters!)

CU Gremlin.

Hi Ulf,

The whole thing about test drives is really strange... because after the introduction of the 6L model with the 96kW engine, the Seat dealerships really "oversold" those cars – mine has two of them (I've already mentioned one of them).

So, it should be available despite the delivery delay... at least here in Berlin (but that might be too far for you).

Best regards,

Jan.

Thomas wrote:

If the fuel injection amount has been reduced compared to the standard condition, and the boost pressure is being regulated according to the accelerator pedal position, the STG (Steuergerät - control unit) continuously closes the VTG (Variable Turbine Geometry) and narrows the cross-section until the desired boost pressure is reached. Due to the lack of exhaust energy caused by the reduced fuel injection amount, the VTG must narrow the cross-section to maintain the boost pressure, which increases the back pressure. ! That's how I imagine it... Improvement desired!

Hi Thomas,

From my point of view, it's completely correct.
Result: Same fuel injection amount + higher boost pressure = higher exhaust gas temperature.
The principle should probably still apply even with the maximum injection amount.

If the engine produces excessive black smoke (like a Russian tank) and the combustion improves with higher pressure, it will also consume more diesel fuel (because less soot is produced).
And because of that, the exhaust temperature will not decrease, but rather will likely increase again.

I once read that the VTG (Variable Turbine Geometry) system can start to malfunction if only the fuel injection amount is increased without increasing the amount of air (due to higher exhaust gas temperatures). If the boost pressure was increased simultaneously, there were no more problems with the VTG adjustment, as the exhaust gas temperature decreased again.

Best regards, WarLord.

Hi,
If the same amount of diesel fuel is burned with more air at a higher boost pressure, the combustion rate will be higher. This allows the engine to better utilize the heat released, which should result in a lower exhaust gas temperature. Whether this will compensate for the increase in intake air temperature (due to the limited effectiveness of the intercooler) can probably only be determined in a real-world setting.

christians wrote:

If the same amount of diesel fuel is burned in more air at a higher boost pressure, the combustion speed will be higher. This allows the engine to better utilize the heat released, which should result in a lower exhaust gas temperature. Whether this will compensate for the increase in intake air temperature (due to the only partially effective intercooler) can probably only be determined in a real-world scenario.

Ah yes, the consideration of "burning speed" has its merits. Learned something new again...

Hello everyone,

to write something else about the issue of sluggishness at higher RPMs:
Yesterday, I had the opportunity to thoroughly test drive a BMW 320d (330 Nm/2000/min, 150PS/4000/min) here in the Ore Mountains (beautiful, hilly country roads), and I have to say that the engine was very impressive. Up to 2000/min, there's not a huge difference in power compared to my AFN engine, but what happens after that is really something special. It's a smooth, powerful revving experience up to over 4000 rpm, with a very pleasant sound. Unfortunately, I wasn't on the highway, but I can imagine that the engine would be much more fun there.

Best regards,
Albrecht.

Hi,

Quote:

Ah yes, the consideration of "burn rate" has something to it. Learned something new again.

That will be it. I'll look into the matter again.
I only know that the exhaust temperature can be brought back to a normal level by increasing the turbocharger boost pressure.

Quote:

Up to 2000/min, there's not a huge difference in power compared to my AFN, but what happens after that is amazing. It's a light-footed, powerful revving experience that goes beyond 4000 RPM, with a very pleasant sound. Unfortunately, I didn't get to drive on the highway, but I can imagine that the engine would be much more fun there.

A "basic AFN Golf 3" with AXG injectors and an additional control unit/chip can be more fun.

Greetings.
Thomas.

Hello Albrecht,

Is the 320d still equipped with the VP44, or has BMW switched to common rail technology?

Greetings.
Thomas.

Hello Thomas,

The 320d has the CR 2 system with a maximum injection pressure of 1600 bar.
The 216 nozzles would no longer be an option for me, as the noise level is completely unacceptable, and the performance gain is hardly noticeable (I've already had them installed and shared my opinion about them).
Even if you increase the AFN (air filter nozzle), you'll still have the problem of too short of a gear ratio on the highway. The problems associated with transmitting high torque in front-wheel drive systems are not exactly pleasant either.

Best regards,
Albrecht.

Hello,

A crucial factor responsible for the 'weak' upper RPM range of PD-TDIs is the maximum permissible ATL (Airflow Temperature Limit) speed. In the 96kW PD-TDI, the ATL speed at the rated power point is approximately 230,000 1/min, while the maximum permissible speed for this ATL is 240,000 1/min. If maximum power is still required at high altitudes (above approximately 2500m), this is where the limitations become apparent; the ATL is operating at its performance limit. Anyone who wants more power at higher RPMs – i.e., more consistent performance – will need a larger turbocharger. A prime example is the ARL PD-TDI, where significant development work was done on the ATL to reliably achieve 110kW. Unfortunately, measuring engine speed with ATL technology isn't as straightforward as measuring temperature. However, many tuners might be shocked, or at least should be, if they saw where their actual ATL engine speeds are. But the ATL Aftermarket also wants to thrive.

Fixed-speed Christmas.
Best regards, SEPP.

Hello Sepp,

What you are writing is absolutely correct, and I hadn't even thought about that in my explanations regarding the temperature .

Best regards,
Albrecht.

Hello Albrecht,

Quote:

The 216 nozzles would no longer be an option for me, due to the absolutely unacceptable noise level, with only a barely noticeable increase in performance (I have already had them installed and have written my opinion about them).

You were it, then. I think that was the only negative comment on the topic.
I certainly don't want to overstep, but there's definitely some kind of mistake that happened.
But that's getting off-topic now! I sent you a private message.



Greetings.
Thomas.

Hello,

Quote:

An important factor that is largely responsible for the "sluggish" upper RPM range of PD-TDIs is the maximum permissible ATL (Airflow Temperature Limit) speed. For the 96kW PD-TDI, the ATL speed at the rated power point is approximately 230,000 1/min, while the maximum permissible speed for this ATL is 240,000 1/min. If the maximum power is still required at high altitudes (above approximately 2500m), then this is where things start to become problematic; the ATL is operating at its performance limit. Anyone who wants more power at higher RPMs – i.e., more consistent power – cannot avoid using a larger turbocharger. A prime example is the ARL PD-TDI, where significant development work was done on the ATL to reliably achieve 110kW. Unfortunately, measuring engine speed with ATL technology isn't as straightforward as measuring temperature. However, many tuners might be shocked, or at least should be, if they saw where their actual ATL engine speeds are. But the ATL Aftermarket also wants to thrive.

It essentially means that the gear ratio is simply a compromise between the impeller speed and the maximum [something - the context is missing here]. Performance (injection quantity) in a PD system.

But why only with the PDs? Does the same apply to VEP-TDI models?
The VNT15 likely has a lower maximum permissible rotational speed than the GT17. For those models, you would likely observe a "sluggish" upper RPM range in relation to the "more responsive" lower RPM range.

Looking back at the development of TDI engines, the injectors (ATL) are becoming smaller and "weaker." Consequently, the power output is also decreasing, which in turn reduces the fuel injection volume. But does this phenomenon seem to be solely related to the injection technology?

Where is the missing part of the thought?

Greetings.
Thomas.

Greetings.
Thomas.

Hmm, don't BMW and DC use larger chargers for their engines? That's probably why they have such a throaty sound and pull strongly at high RPMs. And then there's the drivetrain: front-wheel drive is just for cheapskates.

Best regards, WarLord.

Hello Thomas,

Quote:

I certainly don't want to offend you, but there's definitely some kind of mistake that happened.

The only possible mistake would have been installing the nozzles rotated 180 degrees. I highly doubt that the only consequence would have been a louder running noise.
It was mostly noticeable at idle and under light load. There was no difference in the higher load range, but also no significant improvement in performance! And pay hundreds of euros for that? No way!
It seems that your tolerance level regarding the diesel noise is higher, for example, when Ulf is taking out the last soundproofing mats .

Regarding the chargers: It's not just about the size; there are also ongoing developments and improvements. To have a proper discussion about this, we would need a compressor and turbine characteristic curve with the engine operating line plotted on it.

Best regards,
Albrecht.