Quick recap, so first run of the day I installed the advance piston with the ag db4 cam pin on the stand. We start bleeding the air out and notice our transfer pressure is super high for barely any rpms we are turning to cycle the pump. With the perfect tolerance on the cam pin bore our transfer pressure was at 50psi where we used to have 5. Pulled the inlet fitting and adjusted our transfer pressure regulator down a few times before we got back to a comfortable range. We were pleased to see that the regulator responded very well to adjustments, the pressure was very controllable where previously a hair's width made all the difference.
After getting our pressures dialed in, we noticed our return volume was pretty low, swapped a factory return fitting on, and swapped the #5 vent wire for a #3. Now we had 1-2 psi housing pressure, and a perfect amount of return, where previously we were ******* the flow meter with how much transfer pressure was going out the return. We ran the pump and noticed the governor pulling in a lot sooner, and while bringing the stand rpms down from where the pump was coming clean at 3750 down to 3600ish range, it smacked itself with the hydraulic load as the governor started making fuel again, it shot the advance piston end plug across the room with part of the housing with it, you can even see where the cam pin smacked the slot where it can travel with the advance piston movement:
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Not letting that stop us, we grabbed a freshly sleeved torque screw equipped housing, stripped the original pump, and built the pump again. In the meantime I went to engineering a way to keep from destroying another housing, and found a simple enough way to lock the advance piston in place but have the location and timing of the cam ring be adjustable with a thin stack of shims. By doing that we lost our light load advance arm, but got a much sturdier design.
With a completely new housing, we were able to set everything up to our previous spec before putting it on the test stand by going through my notes from earlier runs, and got a very repeatable setup spec sheet, even with a different housing we were making exactly the same as before. Here is the graph for the initial outputs with the new housing, these numbers are pretty conservative averages, I got peak numbers 10-15cc more but with the spread over several runs this is how it averaged out to give as accurate of a representation of real world performance.
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After that run I played with my shim pack, adjusting our angle of the cam ring to see what gave us the most fuel, then installed some new parts to hopefully eliminate the governor completely from cutting fueling at higher rpms and make a flatter fuel curve. I noticed after modifying the governor, and finding the sweet spot for our cam ring we picked up a lot of fuel and dropped transfer pressure, so I was able to adjust the transfer pressure regulator even more to get more fuel filling the plungers, which told me we were heading the right direction, less pressure means there's less restriction for that transfer fuel trying to get into the plungers, which is what we are trying to optimize for a flat fuel curve.
Notice for this run, I did change the rpm points we tested at because we were pulling at a much higher rpm than before we touched the governor. This setup gave the most fuel down low we saw that day,
315+cc at cranking, and over 220cc main fuel.
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At this point, this pump is really straining the 10hp stand. We have a 20hp stand at the shop, but it is setup for hotrod inlines, and would take a few hours to swap everything over to run this pump on that stand, so we are limited to 5-10 minute runs before we had to let the stand cool down. We would bring the stand rpms up to 2000 rpms, energize the pump, and the stand would drop 200 rpms just from the load of moving the fuel, it was already rotating the pump at that speed, but just the hydraulic load this thing makes was enough to really work this stand over. We've run 3208 cat pumps, stock inlines p7100s and all kinds of ag pumps on this stand and never had anything that pulled it down like that, and this is just a little rotary pump!
Anyways, after that run I wanted to check my idle and then play with the governor some more to try and nurse some more fuel out of the mid to high range. As it was it was idling just under a 1000 rpms, so it would be just under what cold high idle is, which isnt terrible but I wanted this thing to act stock. I set the idle at 700 rpms, and noticed we dropped fuel all over, it seems when you move the fuel curve so far up, it becomes much harder to make resolution to have it just barely dribble enough fuel to idle, intrigued I wanted to see just how much this can affect our overall fueling, and ran the pump set at several idle speeds settings to see what averaged the best, and ended up settling at an 800 rpm compromise.
With the target idle speed there, I spent a few hours just fiddling with shims, guide stud, minimax, transfer pressure and delivery valve settings until I got where I was happy, and we met the goals of our customer. Here is what we ended up with,
300 cranking, 190 main fuel, and 130-110 from 2800-4500+. I know for sure this is going to move more fuel in the truck with our stage ones injectors our customer has, and saw much higher peak numbers throughout the curve, but like before these are averages. I know there's more in this setup, if we were going for all out performance, a higher idle, more transfer and inlet pressure, a more radical governor setup and some more work with the delivery valve would net more fuel, but that wasnt the goal for this pump. This pump still works with the factory high idle and cold advance, takes stock inlet pressures and has an advance curve very similar to a stock pump despite not having the light load advance and with it being a torque screw housing, the pump has a lot of fueling adjustment built in so it can be tuned to put out whatever is needed.
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This has been a big project for us, Ive learned a lot from the db4 platform and am taking away some new data to apply to my db2s, as well as really repeatable recipe for a beast of a rotary pump. Im looking forward to seeing how this thing performs in our customer's rig, and after we get some bulk miles and get a healthy checkup on the pump, this things going to be available on the market.
A big thank you to Justin Anderson, for helping to steer me in the right direction when putting the parts together at the beginning of the project and letting me bounce some questions off him from time to time. Of course a big thanks to the Oilburner's community for being so supportive throughout my endeavours, and for hosting a place for projects and information like this to be shared. We all owe
@Goose_ss4 a thanks for taking the risk in funding this project with no guarantee in its success, and for his patience while I sorted out issue after issue, without guys like him, products like this wouldn't ever get made.
Thats a wrap for this one, cant wait to see whats gonna be done with it!