Warum sind PDs obenraus so "lahm"? | Posts 16+

Hello Uli,

What you're writing is correct. However, even with diesel engines, exhaust gas temperatures can reach levels where currently used variable geometry turbochargers (VTGs) reach their temperature limits. And in that case, with diesel engines, given certain constraints (injection pressure, injection timing, injectors, etc., including costs), there's nothing you can do other than reduce the injection amount, which reduces peak power, which is what we were talking about here .

Best regards,
Albrecht.

Hello Albrecht,

Albrecht wrote:

What you're writing is correct. However, even with diesel engines, exhaust gas temperatures can reach levels where currently used variable geometry turbochargers (VTGs) reach their temperature limits. And in that case, with diesel engines, given certain constraints (injection pressure, injection timing, injectors, etc., including costs), there's not much you can do other than reduce the injection amount, which reduces peak power, which is what we were talking about here

.

If exhaust temperature were actually a limiting factor, then every chip would eventually "fry" the turbocharger. I still maintain that exhaust temperature has nothing to do with Ulf's question. Sure, diesel loaders also get heated up properly, but the power limitations have other reasons.

Best regards, Uli.

Hello Uli,

Quote:

Eventually, every chip would end up frying the poor charger

.

He would do that too! Most modified diesel engines already run at their rev limiter, which in turn reduces the amount of fuel being injected.
I'm not coming up with that idea about the exhaust temperature. I know it specifically from the test bench.
There are quite a few known cases of VTG systems malfunctioning.

Quote:

but the performance limitation has other reasons.

What do you think?

Hello Albrecht,

Albrecht wrote:

Quote: Eventually, every chip would end up frying the poor charger . He would do that too! Most modified diesel engines already run at their rev limiter,

where fuel is then cut off.

And just before that, they're delivering 30-40 horsepower more than intended, without removing anything, and the exhaust is definitely getting hotter than in the stock configuration.

Albrecht wrote:

I'm not making up the thing about the exhaust temperature. I know it specifically from the test bench. There are quite a few known cases of VTG systems malfunctioning. Quote: but the performance limitation has other reasons. Which one do you think?

"I get the impression we're talking past each other. I'm not disagreeing with the general fact that a diesel engine can produce excessively hot exhaust gases above a certain RPM, but rather with the claim made in connection with Ulf's questions that this is a performance-limiting factor for the PD engines. Maybe I misunderstood you, but in any case, the 115 and 130 horsepower engines have a deliberately steep drop in the torque curve (to encourage the driver to shift gears and not exceed the specified horsepower limit), and not because of the exhaust temperature. The 150 horsepower engine maintains its torque for longer, so it's probably possible (with a mechanically modified engine)." In the description

Quote:

see

under "VW News" and there, "110kW P-nozzle" (I can't "steal" the direct link). Among other things, the engine block and the crankshaft are made of a stronger material. http://www.tuneline.at
"It only mentions aerodynamic optimization of the turbocharger. If the exhaust temperature had been a problem in this case, they would certainly have listed the corrective measures."

Best regards, Uli.

Hello Uli,

Quote:

If the exhaust temperature had been a problem in this case, they would certainly have listed the corrective actions.

and what about the much, much larger intercooler ?
You can trust me on this, the exhaust temperature won't be any higher.
The situation is different with "detuned engines," such as the 115 hp PD (experimental PD) or the later 90 hp VE engine with VTG (variable turbine geometry), which had low production costs due to shared components.

Quote:

..., Maybe I misunderstood you, but in any case, the 115 and 130 horsepower engines have a drastically decreasing torque curve intentionally (to encourage the driver to shift gears and not exceed the specified horsepower limit), and not because of exhaust temperature.

That's the thing, the decreasing torque curve is meant to encourage the driver to shift gears , but sorry, that's nonsense.
Now we're back to square one: Do you really believe that all those engineers spent years developing something just to not extract everything that's possible from it? According to this theory, the 150 hp PD wouldn't have needed any further modifications, and the 130 hp model would still have had some reserves. He's doing it because it's simply necessary.


Best regards,
Albrecht.

that's the thing, a decreasing torque curve is meant to encourage the driver to shift gears, but sorry, that's nonsense.
Now we're back to square one: Do you really believe that all those engineers spent years developing something just to not extract everything that's possible from it? According to this theory, the 150 hp PD wouldn't have needed any further modifications, and the 130 hp model would still have had some reserves. He's doing it because it's simply necessary.


Best regards,
Albrecht

I see things a bit differently. The 150 hp engine was developed specifically for top-of-the-line models and was designed to be durable, which is why it was further developed. The components used are significantly more expensive than those of the standard PD engine. It's essentially a prestige engine, in a class where you want to show the competition what's possible, and the customer has to pay for it if they want it. See also V10 TDI - who needs that?

The 130 hp engine is installed in every VAG car and is likely the best-selling engine. To prevent it from breaking down too often, the torque curve is programmed for 'early shifting.' This is probably the 'TDI for everyone' when it comes to buying a car. But he still delivered results.

My opinion!!

Hello,

I think Albrecht's explanation makes sense.

The ARL engine didn't just happen to be the only one to receive a GT1749VB turbocharger; there was a reason for it.
Exhaust gas temperature (and exhaust back pressure) are indeed limiting factors.

Quote:

do nothing except reduce the injection amount, which compromises peak performance, which is what we were talking about here

.

Or, alternatively, increase the boost pressure (and use a larger intercooler). This could also help to lower the exhaust gas temperature. But actually, in most cases, it only depends on the amount and duration of the fuel injection.

Or, one could cool the turbine with water.

Quote:

If the exhaust gas temperature were actually a performance-limiting factor, then every chip would eventually "fry" the turbocharger.

There's always room for improvement. Even with "aggressively" increased fuel injection amounts, the turbocharger boost pressure is still increased, which also has a cooling effect and lowers the exhaust gas temperature. Most turbos fail due to excessively high exhaust gas temperatures or over-revving, which causes the bearings to fail. This often happens in tuned engines.

How many times have there already been threads here about engines failing due to tuning boxes, where only the fuel injection amount is increased?

Quote:

At high speeds and loads, the exhaust gas temperature is usually the limiting factor. You can't use fuel to cool a diesel engine.

Ah, be careful! Weather... *!?$&§$=?* in K. can do that! They told me personally!

Greetings.
Thomas.

Ah, be careful! Weather... *!?$&§$=?* in K. can do that! They told me personally!


Well, that's probably why they filed for bankruptcy right away...

The ARL engine didn't just happen to be the only one to receive a GT1749VB turbocharger; there was a reason for it.
Exhaust gas temperature (and exhaust back pressure) are indeed limiting factors.


What does the 'B' stand for?

My ALH engine has a GT1749V turbocharger (without the 'B').

CU Gremlin.

Thomas wrote:

Or, alternatively, increase the boost pressure (and use a larger turbocharger). This could also help to reduce the exhaust gas temperature. But actually, it usually only depends on the amount of fuel injected

and the duration of the injection.

Hi Thomas,

It's news to me that more boost pressure lowers the exhaust gas temperature.

Briefly, regarding the theoretical background: Starting the injection process earlier, while maintaining the same injection volume, results in more power and thus increases the engine's efficiency.
Therefore, the losses related to exhaust gas temperature must, in the final analysis, be reduced.

Countless everyday experiences with increased boost pressure demonstrate an increase in fuel consumption: specifically, when a faulty mass airflow sensor (MAF) injects less fuel, but the boost pressure is regulated as if it corresponds to the actual accelerator pedal position.
Then the engine's efficiency apparently decreases, leading to higher fuel consumption at the same (partial) load, which suggests the possibility of higher exhaust gas temperatures.

Alternative reason:
More boost pressure requires more drive energy for the turbocharger, which in turn increases exhaust backpressure. And exhaust gases that are more restricted in their expansion towards the exhaust pipe are, in my opinion, hotter than they would be if they had a "clearer path" to the outside.


That's my theory, as far as it goes. Now, you (or someone else) should be able to find a way to circumvent that somehow...

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

He doesn't have any issues with that part; according to him, the engine revs up willingly without hesitation.
and he previously drove a 1.8T until it was completely worn out... so, if he doesn't find the ASZ to be sluggish, then that must be the case .

CU Gremlin.

Gremlin wrote:

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

. . . untuned

Quote:

He has absolutely nothing to criticize about that part; according to his statement, the engine revs up willingly without hesitation... and he previously drove a 1.8T until it was completely worn out... so, if he doesn't find the ASZ to be sluggish, then that must be the case

.

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

Well, let's see how my impressions of the engine in the Polo turn out.
I don't expect significantly more than what's in my Golf: according to the specifications, it's 35 kg heavier, which is 3% more curb weight, but it offers about 10% more torque, while the peak power (Pmax) is the same, meaning a "mere" 3% worse power-to-weight ratio.

Of course, the torque monster will be somewhat in the foreground.
But whether the engine feels constricted at the top, as is often criticized, remains to be seen – I'll be surprised.

Of course, the torque monster will be somewhat in the foreground.
But whether the engine appears constricted from the top, as is often criticized -> I'll be surprised.

Have you driven that engine in any other car before? I'd be surprised if you hadn't, because you can test drive cars with that type of engine pretty much everywhere.

I often drive him in the A4, and he gives me a lot of fun. I don't find him slow at the top end either!

Sure, here's the translation:

'MFG' is an abbreviation for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English.

Wurstblinker wrote:

Have you driven this engine in any other car before? I would be surprised, because you can test drive an engine like this pretty much anywhere.

Hi,

If I were to get one, I would have wanted it to be in the Polo class, so something like a Polo or an Ibiza.
Because "my" 110 horsepower engine in a 1998(?) Passat (I have no idea if it's an AFN) seemed so sluggish that I would never have been interested in that type of engine.
(It's also possible that the Passat's LMM [mass airflow sensor] is faulty).

The Polo with a 96 kW engine is still too new and hardly available as a test car. In this region (Saarland), there are endless delivery delays for Ibizas, and I don't even bother asking about Skodas.

I basically ordered the engine without having it thoroughly checked, except for a few test runs in a Golf 4 Syncro without a bypass. But the power in third gear, starting at 2000 rpm, really surprised me.

Furthermore, I'm not nearly as curious anymore to drive hundreds of kilometers to a dealership just to test drive a car with the 96kW engine that might be "incorrect" in some way.
Next March will surely come - I just hope my new car doesn't fall apart...

Hmmm, mine also runs very powerfully above 3000 RPM and doesn't feel constricted at all. It revs freely up to 4200/4300 RPM, but you can tell it's starting to get sluggish above that. But yesterday I drove an 'old' TDI again, a Passat with 90 horsepower, and you could definitely feel the difference.

Best regards,

Hi,

Quote:

What does the B stand for?

"B" simply refers to the latest generation of the GT17.
This is ONLY used in the ARL (presumably referring to a specific context or system).

Quote:

That more boost pressure lowers the exhaust gas temperature is new to me.

It wasn't meant to imply that you simply increase the boost pressure on a standard engine and then automatically have cooler exhaust gases. No. If you have a "smoke belcher," meaning the fuel injection is *way* too high, you'll automatically have much higher exhaust temperatures. If you then increase the boost pressure again, the exhaust temperature will decrease somewhat. That makes sense.

Quote:

More boost pressure requires more drive energy for the turbocharger, and therefore more exhaust backpressure. And exhaust gases that are more restricted in their expansion towards the exhaust pipe are, in my opinion, hotter than they would be if they had a "clearer path" to the outside.

I agree.

Quote:

Then, apparently, the engine's efficiency decreases -> leading to higher fuel consumption at the same (partial) load, which suggests the possibility of higher exhaust gas temperatures.

Compared to the standard configuration, the fuel injection volume is reduced by some means, and the boost pressure is regulated according to the accelerator pedal position. In this scenario, the STG (control unit) continuously closes the VTG (variable turbine geometry), narrowing the cross-section until the desired boost pressure is achieved. Due to the lack of exhaust energy resulting from the reduced fuel injection volume, the VTG must narrow the cross-section to maintain the boost pressure, which in turn increases the back pressure. That's how I imagine it...


Sure, here's the translation:

"Improvement desired!"

Quote:

Well, that's probably why they filed for bankruptcy right away...

One less!

Greetings.
Thomas.