PD Motor Performance: Optimization & Tuning

Hello,

AFAIK, all 1.9L PD engines have the same camshaft and rocker arms, and therefore the same PDE lift profile during the crankshaft rotation.
By adjusting the timing of the ignition spark, the performance characteristics of the PD engines can be significantly altered, leading to the possibility that an earlier ignition timing would result in more fuel injection at higher speeds and less at mid-range speeds.
This, in turn, would require that the slope of the lifting curve is not constant (e.g., a constant 0.2 mm of lift per degree of KW, a number invented for illustrative purposes), but rather increases over the course of the lifting process.

Does anyone here have more detailed information about this, including the possible total injection angle (from x° vOT to y° nOT) within which an injection is possible?

And does anyone perhaps know the "displacement" of the common PDE engines (ATD, AXR, ASZ) as a theoretical maximum injection amount with the injector fully open throughout the entire stroke?

The context involves a guestbook entry on a website of a dynamic chip tuning company, which claims a power output of 450 Nm on a Seat Ibiza Cupra with a 1.9 TDI engine.
Extrapolating from the series with 60 mg/injection and 330 Nm of torque, at least 82 mg would need to be injected (assuming the same engine efficiency, not to mention the necessary boost pressure or air mass).
However, if the 550 series PDE of the ASZ or BPX engine had a theoretical maximum injection volume (see above) of, for example, only 75 mg, then such torque figures could be refuted purely on a theoretical basis.

Hello Ulf,
Hello,
AFAIK, all 1.9L PD engines have the same camshaft and rocker arms, and therefore the same PDE lift profile during the crankshaft rotation.


'Not quite. If you take an engine from a vehicle with a Diesel Particulate Filter (DPF) and install it in a vehicle without one, you can inject fuel for 15 degrees longer to facilitate regeneration. The camshaft is adjusted accordingly to provide pressure for a longer duration.'


By adjusting the dwell angle (NW), the performance characteristics of the PD motors can be significantly altered, to the point where one might suspect that a shorter dwell angle would result in more fuel injection at higher speeds and less at mid-range speeds.
This, in turn, would require that the slope of the lifting curve is not constant (e.g., a constant 0.2 mm of lift per °KW, a number invented for illustrative purposes), but rather increases as the lifting process progresses.

Sorry, I don't know anything about that.
In my opinion, you can only adjust the timing of the injection pressure relative to top dead center (TDC) by rotating the camshaft. The pressure itself doesn't change. If you want to inject more or less fuel, that can only be done through the software. The PD system is static in this regard.


The context involves a guestbook entry on a website of a dynamic chip tuning company, which claims a power output of 450 Nm on a Seat Ibiza Cupra with a 1.9 TDI engine.
Extrapolating from the series with 60 mg/injection and 330 Nm of torque, at least 82 mg would need to be injected (assuming the same engine efficiency, not to mention the necessary boost pressure or air mass).
If, however, the 550 series PDE of the ASZ or BPX engine had a theoretical maximum injection quantity (see above), for example, of only 75 mg, then such torque figures could already be refuted on a purely theoretical basis.

Okay, I can imagine that a different type of injector is being used here, and that it keeps the valve open for a correspondingly long time. However, the injection pressure drops significantly when the fuel is injected, so that with very long injection times, the remaining injection pressure is quite low.

The absolute chamber volume that can theoretically be extracted should be known to the people who are revising the components.

Best regards, Jochen.

Jochen_145 wrote:

If you take an NW (Nozzle Washer) from a PD (Pump Doser) with a DPF (Diesel Particulate Filter), you can inject for 15° longer to enable regeneration. The camshaft is adjusted accordingly for this purpose and provides pressure for a longer period.

Hi Jochen,

OK, I didn't know that. I'm limiting the search to "all 1.9 diesel engines without a DPF".

Quote:

. . . that the slope of the lifting curve is not constant (e.g., a constant 0.2 mm lift per °KW, a number invented for the example), but increases along the lifting stroke. . . . Sorry, I don't know anything about that right now. In my opinion, you can only adjust the timing of the injection pressure relative to Top Dead Center (TDC) by rotating the cam. The pressure itself does not change. If you want to inject more or less fuel, this can only be done through the software. The PD system is static here.

Well, the pressure inherently increases with the speed, and also with the fuel injection volume due to the compression of the diesel.
Would it be interesting to spin a PD motor in the PDE lifting cylinder and, in the process, capture the stroke of the PDE piston...? Unfortunately, I lack the means to record this even approximately accurately

Quote:

.

The background includes, among other things, a guestbook entry on a dynamic chip tuning website, claiming 450 Nm of torque for an Ibiza Cupra with the 1.9 TDI engine.
. . .
So, I can imagine that a different NW (nozzle) is being used here, and accordingly, the valve remains open for a longer period. }
Certainly not, because that tuner only offers chip tuning, but not engine parts.

I also find that interesting now, because I don't understand it . Based on the logic, I would have probably guessed Jochen...

ulf wrote:

Okay, well, the pressure inherently increases with the speed. 2) and also with the amount of fuel injected, due to the compression of the diesel.

1) Is it because a smaller "amount of leakage" (sorry for this awkward word) results from a shorter compression time? Shouldn't that be negligible?
"The more diesel is injected, the less pressure, right? Pressure is reduced. So, are you (ulf) talking about the amount of fuel being pumped from the filter towards the injector, rather than the injection amount? You want more diesel to reach the injector so that, with the same stroke, there's more pressure... I'm not quite understanding this."

. . . that the slope of the lifting curve is not constant (e.g., a constant 0.2 mm lift per °KW, a number invented for the example), but increases along the lifting stroke.
. . .
Sorry, I don't know anything about that right now.
In my opinion, you can only adjust the timing of the injection pressure relative to Top Dead Center (TDC) by rotating the cam. The pressure itself does not change. If you want to inject more or less fuel, this can only be done through the software. The PD system is static here.
Well, the pressure inherently increases with the speed, and also with the fuel injection volume due to the compression of the diesel.
Would it be interesting to spin a PD motor in the PDE lifting cylinder and, in the process, capture the stroke of the PDE piston...? Unfortunately, I lack the means to record this even approximately accurately .


But why does the pressure increase as the speed increases?
As I understand the principle, the pressure in the PD (presumably referring to a positive displacement system) is determined solely by the stroke of the piston, which is constant and independent of the engine speed. It is determined only by the gear ratio of the rocker arm and the profile and shape of the cam.

If the pressure were dependent on the engine speed, I would have to measure the pressure, similar to what is done with CR systems, in order to determine the injection quantity. However, this is not done.

We haven't measured the PD (presumably referring to a specific parameter) yet, as far as I know. Maybe Barfische knows something about it?




The background includes, among other things, a guestbook entry on a dynamic chip tuning website, claiming 450 Nm of torque for an Ibiza Cupra with the 1.9 TDI engine.
. . .
So, I can imagine that a different NW (nozzle) is being used here, and accordingly, the valve remains open for a longer period.
Certainly not, because that tuner only offers chip tuning, but not engine parts.}

When you look at pressure profiles during the compression phase of PD injection, you can see how quickly the high pressure drops when the injector opens. Therefore, simply 'allowing' the injector to open will not result in a proportional increase in injection quantity.

Best regards, Jochen.

Jochen_145 wrote:

But why does the pressure increase with increasing speed? As I understand the principle, the pressure in the PD is determined solely by the piston stroke, which is constant and independent of the engine speed. It is determined solely by the gear ratio of the rocker arm and the slope and shape of the cam.

It's just the old story about the perfume atomizer again.
If you press the cap down slowly, the broth will tend to drip out of the nozzle rather than being atomized.
If you press quickly (high engine speed), you get a fine atomization. At the same time, the stronger resistance of the cap indicates that the pressure in the pump is higher .

In the PDE (Pre-Injection Device), the diesel fuel is also compressed under enormous pressure. This means that the pump piston delivers a larger volume than can pass through the injection nozzles in the same amount of time. Therefore, the difference in volume between the amount delivered and the amount that flows out (and thus the injection pressure!) increases as the injection duration increases, i.e., as the amount of fuel injected is greater.

Quote:

If the pressure were speed-dependent, I would have to measure the pressure, similar to what is done with CR systems, in order to determine the injection quantity. However, this is not done.

Given a specific PDE (positive displacement element) geometry, along with the hole size, the stroke profile of the swashplate, and the rocker arm ratio, the pressure will always be the same under identical conditions (speed, swashplate angle duration, etc.).
Therefore, it is sufficient to define the relationship between quantity, speed, and duration in characteristic curves, which the EDC uses when controlling the positive displacement pump (and ignores the pressure).

Quote:

When you look at pressure profile diagrams for PD during the compression phase, you can see how quickly the high pressure drops when the PDE opens. Therefore, simply "opening" the valve will certainly not result in a proportional increase in injection量.

Hm? Don't confuse the solenoid valve with the PDE.
Magnet de-energized = valve open = no injection = PDE "closed".
I meant by "longer opening time" the extended duration of the closed state of the solenoid valve – in the extreme case, for as long as the flow curve of the nozzle is still rising.

It's just the old story about the perfume atomizer again.
If you press the cap down slowly, the broth will tend to drip out of the nozzle rather than being atomized.
If you press quickly (high engine speed), you get a fine atomization. At the same time, the stronger resistance of the cap indicates that the pressure in the pump is higher .


Yes, you are right!
I just found it again. My theory only works if the volume in the PDE remains constant, but it doesn't, due to the injection process.


When you look at pressure profile diagrams for PD during the compression phase, you can see how quickly the high pressure drops when the PDE opens. Therefore, simply 'opening' the valve will certainly not result in a proportional increase in injection量.
Hm? Don't confuse the solenoid valve with the PDE.
Magnet de-energized = valve open = no injection = PDE 'closed'.
I meant by longer opening time the PDE, which means a longer closing duration of the solenoid valve - in the extreme case, for as long as the delivery curve of the NW lasts.

I expressed myself somewhat unclearly, but I meant exactly what you said.
So, the high pressure drops significantly when fuel is injected, meaning the valve is closed.
If the valve is open, high pressure cannot build up.
Therefore, simply closing the valve (as mentioned above, but now correctly written ) does not cause a proportional increase in the injection amount, despite the constant movement of the pump piston.

Best regards, Jochen.

@Ulf
You can measure the backlash by attaching a dial gauge to the rocker arm.
You always have to do that when you perform a basic adjustment of the engine control unit (ECU) after installation or removal.
Of course, I didn't pay attention to the size. You don't need to when doing that.
"In any case, I could see that the camshaft lobe is very steep and flat, and that it stays at its highest point for a long time. I would estimate that about 1/4 of the distance is the lift, 2/4 is the overlap at top dead center, and 1/4 is the descending side of the lobe."

The thing about the 450 Nm is nonsense anyway, because, as far as I know, the transmission can only handle up to 350 Nm. Or does the Cupra have a different transmission than the ASZ's 6-speed?

Jochen_145 wrote:

So, the high pressure decreases significantly when fuel is injected, meaning the valve is closed. If the valve is open,

then high pressure will not build up.
There's a contradiction in itself.
(Magnet) Valve open -> no high pressure = correct.
Where is the sudden high pressure supposed to come from, which drops again when the (magnetic) valve is closed? A PDE (Pressure Energy Dissipator) does not have a special high-pressure pre-charge function .

That's correct:
The solenoid valve closes -> the high pressure builds up, overcomes the nozzle opening pressure, and the injection begins (I'm omitting the pre-injection function here, as it doesn't change the principle).
Because more fuel is injected than can drain through the leakage holes, the pressure continues to rise during injection until the solenoid valve opens -> the pressure drops, the nozzle closes, meaning the injection ends.

Quote:

Therefore, simply closing the valve (as mentioned above, but now correctly written ) does not cause a proportional increase in the injection amount, despite the constant movement of the pump piston.

IMO, yes, as long as the uplift side of the NW structure is still rising.

Quote:

You can measure the lift by attaching a dial indicator to the rocker arm.

Unfortunately, I don't have anything "sophisticated" like that -> I use other "guessing tools" (see the technical article on NW adjustment). :(These are sufficient to determine the full travel of the PDE camshaft, but not to determine the lift profile.
Even if I had a protractor, I would still need to be able to precisely rotate the quadrant in small increments, but without a platform, that's also quite tedious.

Quote:

The thing about the 450 Nm is nonsense anyway, because, as far as I know, the transmission can only handle up to 350 Nm. Or does the Cupra have a different transmission than the 6-speed one from the ASZ?

The transmission is fundamentally the same, but it doesn't fail immediately at 351 Nm; it can actually handle significantly more (for a short time). However, in the process, it ages rapidly, which means that statistically, its lifespan is shorter.