Long story short, the scavenge pump on my truck stopped working. I don't know why, don't really care why, I think it was an ebay special to begin with so was probably only good for intermittent use and burned out the brushes already.
Because I'm on the "You're an adult and can't modify cars anymore" budget the fix has to come from the pile of parts I have.
I was looking at power steering pumps. I mean, not just staring at one on the bench, but figuring out what design they are and how they work. Found that they are capable of pumping 15-20 GPM, are a vane style pump, with some interesting design differences from the one in the transmission to make them handle the 1500psi range. https://www.pirate4x4.com/forum/gen...IPjegxU8anZXZrQy9zb6lG_tpkx5ikgpCc1xTGgYShOd4
There is no center ring for the vanes to ride. A combination of centrifugal force and outlet pressure push the vanes out (and hold under high pressure), so there is no center ring to wear/crack/break under high pressure. This also means that as configured in power steering systems, it needs to be 'submerged' in the reservoir to build pressure because it can't really pull much vacuum when dry.
In my mind all it needs is a pressure differential where the inlet pressure is higher, and of course it can't run dry. In order to run it as a scavenge pump it needs a few specific changes made to the configuration. The first thing to note in the design is it's basically two pumps in parallel, and there is a gap that carries fluid from the outlet back to the inlet (very low volume). So you could in theory mount the pump below a reservoir, aka the oil pan, where the pump outlet directly connects to the bottom. This would allow oil to back-flow into the pump and maintain lubrication. It also seals up the pump, so it would pull suction because centrifugal force alone is enough to spread the vanes. Backflow volume is low enough that it shouldn't pool up in the intake side, and because there is minimal incoming oil it would be nearly impossible for it to build pressure and whine.
I guess I'm looking at this and thinking why nobody ever done what I thought, at least in grassroots/backyard engineering. It's probably not going to work well with rear mounted turbos or anything where the oil pan is low mounted. Anyway, It's a high flow pump that can handle very high pressures, they last forever, and every car has one so it's an easy junkyard pull. The downside is it has to be mounted below the oil level in the pan so that gravity pressure on the 'outlet' side can backflow oil into the pump. Aside from probably having to add a belt, I don't see this as a real problem in my truck. But you could also use this as a belt driven oil pump (with a large enough pressure regulator to keep up with the flow) if you wanted to see rock solid 100psi oil pressure at idle lol.
Because I'm on the "You're an adult and can't modify cars anymore" budget the fix has to come from the pile of parts I have.
I was looking at power steering pumps. I mean, not just staring at one on the bench, but figuring out what design they are and how they work. Found that they are capable of pumping 15-20 GPM, are a vane style pump, with some interesting design differences from the one in the transmission to make them handle the 1500psi range. https://www.pirate4x4.com/forum/gen...IPjegxU8anZXZrQy9zb6lG_tpkx5ikgpCc1xTGgYShOd4
There is no center ring for the vanes to ride. A combination of centrifugal force and outlet pressure push the vanes out (and hold under high pressure), so there is no center ring to wear/crack/break under high pressure. This also means that as configured in power steering systems, it needs to be 'submerged' in the reservoir to build pressure because it can't really pull much vacuum when dry.
In my mind all it needs is a pressure differential where the inlet pressure is higher, and of course it can't run dry. In order to run it as a scavenge pump it needs a few specific changes made to the configuration. The first thing to note in the design is it's basically two pumps in parallel, and there is a gap that carries fluid from the outlet back to the inlet (very low volume). So you could in theory mount the pump below a reservoir, aka the oil pan, where the pump outlet directly connects to the bottom. This would allow oil to back-flow into the pump and maintain lubrication. It also seals up the pump, so it would pull suction because centrifugal force alone is enough to spread the vanes. Backflow volume is low enough that it shouldn't pool up in the intake side, and because there is minimal incoming oil it would be nearly impossible for it to build pressure and whine.
I guess I'm looking at this and thinking why nobody ever done what I thought, at least in grassroots/backyard engineering. It's probably not going to work well with rear mounted turbos or anything where the oil pan is low mounted. Anyway, It's a high flow pump that can handle very high pressures, they last forever, and every car has one so it's an easy junkyard pull. The downside is it has to be mounted below the oil level in the pan so that gravity pressure on the 'outlet' side can backflow oil into the pump. Aside from probably having to add a belt, I don't see this as a real problem in my truck. But you could also use this as a belt driven oil pump (with a large enough pressure regulator to keep up with the flow) if you wanted to see rock solid 100psi oil pressure at idle lol.
