Bosch's specifications for the rated speed of a VEP

Hi everyone,
I have a question regarding understanding.
Here are the details from Bosch regarding two VEPs:

ACV
0 460 415 983
VE5/11E1750L714-1

VE= Distributor Injection Pump
5 = Number of cylinders
11 = Piston diameter
E = Electrically controlled
1750 = Nominal Speed Pump
L = left-hand turn

AAT
0 460 415 994
VE5/11E2300L460-1

VE= Distributor Injection Pump
5 = Number of cylinders
11 = Piston diameter
E = Electrically controlled
2300 = Rated Speed Pump
L = left-hand turn

I am interested in what Bosch means by specifying the "rated speed". The two examples are very similar VEPs, but with very different specified rated speeds. Since these are electronically controlled VEPs, it can hardly be the operating range of the VEP that is determined by the program in the engine control unit.
Does the rated speed provide any indication of mechanical construction differences?

Hi,

That's fine, the pump is just running at half the engine speed.

Hi, Rainer

Thank you for the response, unfortunately, I don't understand it.
I chose the two ESPs only as an example, because they have such different names despite having almost identical engines.
What does Bosch now mean by specifying the rated speed?

Do the two fuel injection pumps differ in any mechanical components?

Hello,

I suspect that things like the pump plunger's feathers and flow behavior during pumping play a role, basically anything that can cause problems at higher speeds.

My advice is to get the right pump, unless you have a lot of time to adjust the pump settings.

Best regards, Rainer

Hi,
As far as I've been able to find out, the nominal speed of the VEP is the speed with the highest injection volume per stroke.
That also makes sense; once a meaningful value for the engine speed is reached, the injection volume of the pump must be gradually reduced, otherwise the engine's torque will continue to increase, etc. There must also be limits for the flow rate in the VEP and in the fuel supply, for example, due to cavitation or vibrations in the lines.
The engine with the ECU, the charging system, the fuel injection system, and the MSG are, of course, all coordinated and tuned for the vehicle, resulting in a specific torque curve, power output, and exhaust gas behavior.
The two pumps you mentioned belong to motors with significantly different torque characteristics and power output.
hg
Herbert

Quote:

is the stoichiometric injection rate of the VEP, which is the injection rate with the highest amount of fuel per stroke.

At 2000rpm, the fuel injection pressure is much lower than at 4000rpm, because there is simply more time available to press the fuel through the nozzle.

The stroke of the pump piston is always the same.

Therefore, it will likely not be the case that the highest (possible) injection volume per stroke is at the highest (possible) speed.

Or do you mean it differently?

I was primarily focusing on the VEP with internal mechanical regulation (and, in fact, further research actually shows a relationship between rated speed and braking speed).
In the case of the EDC-controlled VEP (VP37), there is no longer a control loop within the pump. Therefore, the purpose of the stated rotational speed here is not clear to me.
The two engines, AAT (Audi C4) and ACV (T4), differ significantly in terms of power, torque, and speed characteristics. The values for speed at Pmax (3500 min-1) and rated speed (1750 min-1) are consistent for the ACV, but not for the AAT. As long as the performance differences are achieved through different injection volumes, the stroke should be different (maximum delivery volume) for the same piston diameter, which corresponds to the same volume of the fuel injector.
hg
Herbert

Hi everyone,
Thank you for your input.
I haven't yet figured out the issue with Bosch's specification for the rated speed in electric vehicle powertrains (E-VEP).
The Audi AAT and the T4 ACV engines are quite similar. Both engines use the same turbocharger (in terms of size and performance characteristics), the KKK K14 (at least in its original equipment version, and in Audi vehicles only in the A6; the Audi 100-AAT had a K16).
The injector size is the same, but the exact design is different. The nozzles are not interchangeable.
The ACV has a motor rated speed of 3500 rpm, as specified by MSG, which is consistent with Bosch's specification for the VEP.
The Audi AAT engine has a nominal speed of 4250 rpm.
Audi specifies 115 horsepower at 4250 rpm and 265 Nm of torque at 2250 rpm.
Unfortunately, I couldn't find any power/torque curves for the AAT engine online; I only found them for the 1T, which was the very first TDI engine produced by VAG, and for the direct predecessor of the AAT.
I am sorry, but I am unable to translate the provided URL as it is an image link and not a text-based document.

Here are the resources for the ACV:
I am sorry, but I am unable to access external websites or specific files online, including the one you provided. Therefore, I cannot translate the text associated with that image.
At 4250 rpm, the ACV in the T4 has almost no power, and the MSG has already significantly reduced its output.
Power and torque are related by a fixed ratio.
P = (M * n) / 9549

At the rated speed of the ACV (3500 rpm), the AAT has almost the same engine power. However, the AAT's power continues to increase up to 4250 rpm, while the ACV's power begins to decrease.

The area above 4000 rpm is quite demanding for the TDI engine; the injection times are very short in order to get the necessary amount of diesel into the cylinder.

To pick up on Herbert's idea regarding the pump hub:
The stroke, resulting from the camshaft (stroke?) disc, is always the same mechanically. The product of the piston diameter and the stroke determines the geometrically maximum possible injection amount. Regardless, many other factors come into play in reality.
Do you need more stroke length for a higher rated speed? I don't really understand that.
The mass airflow sensor electronically controls the maximum fuel injection amount. However, I can't imagine that the engine's vacuum pressure (VEP) at 1750 rpm would be at the mechanical limit of the fuel injection amount. That would mean that even by changing the programming in the engine control unit (ECU), it wouldn't be possible to increase the power output above 3500 rpm. To the best of my knowledge, that is not the case. By modifying the characteristic maps, an ACV-VEP (an engine control unit) can still inject enough diesel fuel at higher engine speeds.

The question about the "Bosch nominal speed" might be theoretical, but I am still very interested in it.
Unfortunately, I can't just call Bosch and ask. And the usual repair shops that specialize in common rail diesel pumps also don't know anything about it.

Hi,

As you can see from both torque curves, the torque drops significantly above 3000 rpm, which means the amount of fuel injected per cycle also decreases. Specifically, it's so significant that it doesn't matter whether the pump can still deliver the full injection amount when operating above its rated speed.

Best regards, Rainer.