VP37 Standalone Controller: Features & Benefits

Hello fellow diesel mechanics.

My name is Reini, and I've been working on engines for about 20 years, mainly on US engines, but also on my everyday cars, which are mostly older Audis... AEL, AAT, ASE, AKG, MC, 3B, etc.
Professionally, I work in the research and development department of a well-known electronics company.

about the topic of

It's about signals from VP37.

My plan is to use a 1.9 SDI engine to power a generator.

I've also created a printout that monitors oil pressure, coolant level, coolant temperature, battery status, dual speed monitoring with a hard cut-off, preheating, and other parameters.

The HDK is considered a transformer with an adjustable core, which works well. Specifically, the side with the fixed short-circuit ring is subjected to a 10 kHz sine wave at 10 Vss, resulting in 1-2 Vss at the other end, which is easily measurable.

The MSW is still voltage-controlled via a buck converter, using feedback control.

Upon initial power-up, the MSW is calibrated by being moved to its end-of-travel position. It then measures its position based on the HDK value. If the control ring experiences a position-dependent clamping issue, the system will start for 2 seconds and then initiate another calibration sequence.

It has been shown that I need a relatively high initial injection amount, and it must be reduced immediately after starting.

My problem is this: the engine starts, but immediately goes into a regulated state. The engine then stays at a certain RPM, which slowly increases and then suddenly jumps up rapidly.

I simulated this with DC power on the MSW. I need 3.5 amps to start, but I have to immediately reduce it to 3 amps, and then back up to 3.36 amps (that's the actual number) to keep the motor running (in an unstable idle state). Then, it slowly increases again, and suddenly it spins up very rapidly.

My initial suspicion was that it was a problem with the injection start regulator, so I blocked it, but the result was the same... I also tried actuating it, and it produced white smoke, so it's working. Since the injection start depends on the internal pump pressure, at what speed does the internal pump pressure actually build up?

I hope I can ask you a few questions.

"In the future, I will be controlling the MSW with a 500Hz PWM signal. As I understand it, a PWM value of approximately 20-30% corresponds to the range between 0 and full output. This means that the PWM needs to be very finely tuned. This might also help with the dosing process, because the control ring seems to "vibrate" into its position."

Would it help to adjust the injection timing to a later setting in idle to reduce power? For example, with AEL, it seems to be at an 80% duty cycle in low load.
"When running in combined mode, I would like to start at 1000 rpm for 1 minute, then increase to 1500 rpm... so I don't need a significant adjustment to the injection timing."

The pump return flow is actually quite constant at both low and high speeds, and doesn't change much. Is this normal, or is the suction line limiting it (which I don't think is the case, since it's relatively short and has a diameter similar to the original)?

I would be very grateful for any feedback, as there are not many true experts on the VP37 and its control.

Thank you.

Reini.

Hello Reini,

It sounds like the quantity control valve is being regulated. However, this doesn't work that way with this type of injection pump, as there is no internal regulation whatsoever. In mechanical injection pumps, the regulation is implemented in "hardware" and built into the pump.
In SDI/TDI engines, this function is handled by the engine control unit (ECU).
Without a functioning system in place, nothing can be achieved, so all your other questions are a lower priority.

So, you either create your own tuning solution or have the engine control unit (ECU) adjusted accordingly. A sharp limitation of torque from a certain engine speed shouldn't be too difficult for even average chip tuners.

Best regards, Rainer.

hello Rainer,

Thank you for your reply.

Well, there is a system in place, although it's still quite basic, but in principle, it should work...
What I still need to change is that I'm currently using a voltage-driven system, which is converted into current through the coil resistance, and that current then drives the motor. That's definitely not the right approach, and I'll soon switch to a 500Hz PWM system.

I built a simple PWM (Pulse Width Modulation) stage for the MSW, which I operate using a frequency generator.
At a 25% duty cycle, the motor starts to move away from the zero position, and at 35% it reaches the end position. This means that, effectively, I only have a 10% difference between the zero and full positions. Considering the non-linearity, only a maximum of 5% duty cycle is available for control, which isn't much.

It would probably be best to use a current clamp with an oscilloscope on a running vehicle to measure the actual current levels.

Thank you.

Reini.

To be upfront: I'm not an expert on the VP37. However, what I do know is that the MSG (Motor Speed Governor) not only regulates the engine speed, but also controls the idle speed stabilization.

The standard motor runs up to >4000 rpm, which is 66 revolutions per second. However, your PWM is only running at 500 Hz. I suspect that your control speed is still far below the output signal. I believe that your control system is likely too slow to properly regulate the motor.

Regarding the sudden load surge/increase in your engine's speed: Could it be that the preheating cycle is ending, causing the load to decrease? Keep in mind that the load has a much greater influence on the required fuel injection amount than the engine speed. (What I mean is: Without a load, you can easily bring the engine to its maximum speed with a very small increase in fuel injection / (slight accelerator pedal pressure). Any change in load has a significant effect.)

In short: You will probably have to fine-tune and adjust things much more precisely and quickly.

Regards,
Guste.

hello Guste,

Thank you for the feedback.

A picture is slowly starting to emerge.

In the initial tests, almost no diesel fuel was returning. It turned out that the impeller vanes of the pre-injection pump were stuck, preventing any pressure buildup, and the regulator had no chance of maintaining any speed. This issue has now been resolved, and I'm now getting a large amount of diesel fuel returning.

The afterglow feature is not yet implemented. I'm already running the engine with a standalone controller, which has a pre-glow function, but (not yet) an afterglow function. I'll implement that once I've worked out the speed control .

"I completely agree with you; there's approximately 100mA difference in current between the motor stalling and running at full speed. However, I was directly powering the motor with electricity, and... if I quickly adjust the current regulator up and down by hand, I can maintain a certain speed. If I can incorporate this into a regulator that is much faster and more precise than I can manually adjust, then it might work."

If anyone is interested, I'd be happy to keep you updated.

Best regards,

Reini.

Reini wrote:

If anyone is interested, I'd be happy to keep you updated.

Sure, I'd be happy to.

I would be very interested to see how well you manage to optimize your "self-built engine control unit."

If you could mention a little more about the background, I would also be curious (both the intended use of the generator and the hardware and software used in your MSGs). It sounds like it could be fascinating bedtime reading .

I'm not sure how it works with the electronically controlled VP37, but with the mechanical VP series, only the idle and maximum speed are regulated. Therefore, I suspect that if the VP37 works the same way, it might be difficult to use it in generator mode, unless the generator always produces the same amount of power.

The VA series, which uses hydraulic regulators, provides control across all speed ranges.

Hi,

For generator operation, I would simply implement a speed control system. If the actual speed is lower than the target speed, increase the fuel supply; if the actual speed is too high, decrease the fuel supply.
https://rn-wissen.de/wiki/index.php/Regelungstechnik
https://github.com/tekdemo/MiniPID
https://github.com/pms67/PID

Best regards, Rainer.

Hello everyone.

It's been some time, but I would still like to provide a brief update. The standalone controller is running, has been under constant power for about a year, and is working perfectly.
The MSW is controlled with a 500 Hz PWM signal, starts up perfectly in both cold and warm conditions, and also regulates the required 1500 RPM well and dynamically. Load changes on the generator, from 0 to 12 kW and back, are very well compensated for.

Thank you again for your answers.
Best regards,
Reini.

Is there a schematic diagram and source code available so that people can replicate it?