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-   -   VP44 Standalone ECU Project (http://www.competitiondiesel.com/forums/showthread.php?t=202024)

zachu812 01-29-2019 03:21 PM

VP44 Standalone ECU Project
 
3 Attachment(s)
Title says it all, I've had this idea for years but haven't had the time and resources to start on anything until recently. Go figure it's after I ppumped the truck, now it's more about seeing what these pumps are capable of and learning something along the way. I'm an electrical engineer by trade so I've got a good start on the electronics portion of things but my software skills are pretty rusty, gonna have a lot to figure out there. I'm open to ideas when I get to that point.

This all started when I took a VP44 apart a few months back and came to the conclusion that the pump itself is capable of moving a decent amount of fuel, the biggest problem it seems is the timing piston galling and locking up. Once this happens the PSG gets all confused and starts doing weird stuff then people blame it on the electronics. I've got some ideas to fix the timing piston problem, or at least to help it live, but that can wait until I get a pump running on a truck. I want to set the code up so the pump still runs fine with static timing, none of that dead pedal crap.

Attachment 71857

My plan to start is making an Arduino Due based standalone ECU that only references the internal pump position sensor and fires the fuel solenoid. Timing, map based fueling, and all that can wait until I've got something running. I started by pinning out the pump sensor, it has a ground, 5V supply from the PSG, and two outputs. I was hoping for a nice 0-5V logic level signal when I spin the pump but wasn't that lucky. The output almost looks like something from a variable reluctance sensor with some DC offset but the voltage doesn't seem to change with speed. At first I thought it was a differential signal but I think there's actually 2 sensors offset slightly. You can see each sensor output on the blue and yellow lines in the scope plot below, the red line is what happens when the wires are connected together. The higher points on the sensor outputs are actually dips on the pumps internal tone wheel, there are 6 of these evenly spaced so the plan is to use these as reference points to time the injection events.

Attachment 71858

Next step is to turn whatever the pump sensor is putting out into a usable 0-5V signal. I put together a circuit simulation with a couple op-amps and it seems to do exactly what I'm looking for. The red trace is a simulation of whats coming out of the sensor, green trace is after I remove the offset, and the blue trace is the 0-5V signal I'll be able to feed into the Arduino. Getting these results on an actual circuit might be another story but it's doable, I'll get started on that when I'm back from this business trip next week.

Attachment 71859

jasonc 01-29-2019 03:56 PM

Very interesting.

J-Pipes 01-29-2019 04:04 PM

Not going to lie, I understand about zero of that, but it's cool to see someone taking a fresh look at the VP44! Watching the progress.

Sent from my SM-G960U using Tapatalk

Mark Nixon 01-29-2019 04:22 PM

Thing is, the electronics on the VP44 engine ARE, in fact, junk.
That argument got put to bed many years ago, IMO.

The VP44 is just a VE with an electronic befuddler attached. :hehe:

Now that I have lashed out at a thing I feel is problematic, I will say that if someone can look at the VP44 and create a whole new way to run it successfully, I'm all for it, as the pumps do have a lot of potential.

Right now, though, if people ask me for replacement ECMs, I usually just look at them and shake my head.
Many of those trucks have died because the electronics truly ARE...junk.

Mark.

wwentzler 01-29-2019 09:44 PM

Didnt know you were an EE. Sounds neat, my buddy whom I'm fairly certain you know (name starts with an R) had been talking about this about this time last year. I think it's certainly doable, and sounds like you've got a decent start.

WUnderwood 01-29-2019 10:11 PM

Quote:

Originally Posted by J-Pipes (Post 2692432)
Not going to lie, I understand about zero of that, but it's cool to see someone taking a fresh look at the VP44! Watching the progress.

Sent from my SM-G960U using Tapatalk



Exactly what I thought as well. Good luck!

Hdhorton 01-29-2019 10:51 PM

In on this one

zachu812 01-30-2019 01:43 AM

Quote:

Originally Posted by wwentzler (Post 2692461)
Didnt know you were an EE. Sounds neat, my buddy whom I'm fairly certain you know (name starts with an R) had been talking about this about this time last year. I think it's certainly doable, and sounds like you've got a decent start.

Yup I've been talking with him along the way, it was actually a few things he told me that clicked when I pulled the pump apart. He's thought a lot more into the control strategy so I wanna try to get him involved when the time comes.

dieselbeef 01-30-2019 06:33 AM

im in on this..vp life.......

99GreenCummins 01-30-2019 07:44 AM

You beat me to the punch! This was my next winter plans. I believe that it will be a complete waste of money and a bunch of wasted parts because of common rail technology. I feel like it is a forgotten technology that has a chance. I love my VP and would love to compete in 2.5 class.

wwentzler 01-30-2019 08:07 AM

As far as the circuit it looks good, (I hate ltspice but its useful af). If you use semi decent quality components I would imagine the circuit will operate close enough to at least get a rough start on making it work.

weazel 01-30-2019 08:40 AM

Hmmm interesting... in to see how this goes

thatguy69 01-30-2019 09:09 AM

Gotta say my vp has treated me well,i know I'm one of the few. Be interested to see what you come up with

paulb 01-30-2019 01:57 PM

I like the thought of a replacement PSG. I've been custom tuning the ECM for awhile now, and the PSG always comes up as a road block. There have been flaws (and improvements) to the VP44, but there is a reason so many people hang onto this trucks. My 02 has 310,000 miles and over 1600 1/4 mile passes and the bottom end has never been apart.

If there is anything I can help with the project let me know.

Paul

zachu812 01-30-2019 02:40 PM

1 Attachment(s)
Quote:

Originally Posted by wwentzler (Post 2692492)
As far as the circuit it looks good, (I hate ltspice but its useful af). If you use semi decent quality components I would imagine the circuit will operate close enough to at least get a rough start on making it work.

The program is kind of a pain but it's a good starting point. I did some more thinking and got a better handle of what the circuit is actually doing, it's just a comparator that pulls the output to VCC+ or VCC- based on the inputs relation to the reference voltage. Knowing that I was able to get rid of the other 2 parts of the circuit and just change the voltage divider to set reference in the middle of the sensors waveform.

Attachment 71864

Quote:

Originally Posted by paulb (Post 2692522)
I like the thought of a replacement PSG. I've been custom tuning the ECM for awhile now, and the PSG always comes up as a road block. There have been flaws (and improvements) to the VP44, but there is a reason so many people hang onto this trucks. My 02 has 310,000 miles and over 1600 1/4 mile passes and the bottom end has never been apart.

If there is anything I can help with the project let me know.

Paul

What do you use tune the ECM on these trucks? It's a shame the PSG doesn't allow more adjustment, it really is a pretty neat module. I'm sure the information is sitting in a file cabinet somewhere.

Thanks for the offer, I might have some questions for you when it comes time to write the software.

joefarmer 01-30-2019 03:28 PM

How fast were you spinning the pump to get the signal in the scope? 240rpm? Depending on the sensor it wasn't fast enough to get a voltage difference.

Have you thought of using an IC to handle the sensor to uC? There's a few out there depending on the sensor involved that are cheaper than individual components.

AKDieseL 01-30-2019 08:16 PM

I'm headed towards P-Pump as well, but I'm gonna rubber neck the hell out of this thread. Not understanding a lot of the technical stuff, but I've always been hungry for knowledge on pretty much anything. And when it comes to Diesels, especially 2nd Gen Cummins, i can never get my fill.

PRINCETON_JAKE 01-30-2019 09:24 PM

What is a psg? I don’t know much about the vp44 but isn’t it a mechanical pump with electric over mechanical timing? It’s not like you can adjust pressure or pulse electronically, and your stuck with mechanical injectors.

zachu812 01-31-2019 04:36 AM

Quote:

Originally Posted by joefarmer (Post 2692526)
How fast were you spinning the pump to get the signal in the scope? 240rpm? Depending on the sensor it wasn't fast enough to get a voltage difference.

Have you thought of using an IC to handle the sensor to uC? There's a few out there depending on the sensor involved that are cheaper than individual components.

Yea the pump was spinning a little over 200rpm in that scope capture, I've started turning it about 500 rpm with a drill since then. I don't have any scope captures but I can say that the voltage levels didn't seem to change.

I'd love to have an IC that I can just feed the sensor output into and get a logic level signal out but I'm still trying to figure out exactly what kind of sensor it is. My best current guess is a magneto-resistive sensor and I can't find an IC to read that.

Do you have any ideas on they type of sensor or even something to read it? The sensor has 2 outputs, both are reading around 250mv pk-pk normally and 500mv pk-pk on the larger dips for injection timing. One has a 2.5V offset, the other has a 2.75V offset.

Quote:

Originally Posted by PRINCETON_JAKE (Post 2692563)
What is a psg? I don’t know much about the vp44 but isn’t it a mechanical pump with electric over mechanical timing? It’s not like you can adjust pressure or pulse electronically, and your stuck with mechanical injectors.

The PSG is the computer that's mounted on the VP44, it controls the injection quantity and injection timing of the pump. The PSG receives a generic fuel and timing request from the Cummins ECU and controls both solenoids accordingly. It can't adjust injection pressure but it does adjust the pulse electronically. Unfortunately the PSG cannot be tuned freely so we don't have full control over fuel and timing.

PRINCETON_JAKE 01-31-2019 05:15 AM

I can not see how it can adjust pulse electronically when the injector is fired by mechanical/fuel pressure. The only way to adjust pulse on a mechanical injector would be increased pressure to open it sooner and longer, or by providing pressure to it sooner or latter, but from what I see that’s controlled by the rotor/head of the pump which I don’t understand how that would be possible.


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