Dry Sump Scavenge Pump

[NickV]

Hi All,

I was wondering what types of scavenge pumps teams were using on their dry sump setups. We run a post 07 cbr600rr, and currently use the same g-rotors as the stock engine for our scavenge pumps, however I am not sure if the g-rotors are well equipped to move foamy oil. I have a feeling that they create cavitation issues at high rpm with foam. I have also heard of the roots style pumps utilized by dailey engineering, so any experience with them would be appreciated. Does anyone have any positive experience with using g-rotors as scavenge pumps? I'm not necessarily concerned with the implementation, rather just what types of pumps work as scavenge pumps.

Thanks for your opinions

[Drew Price]

I thought most of the scavenge style pumps I have seen are sliding vane pumps rather than rotor or gear style pumps, it always seemed to me like they would self-prime easier, but if your pump is really down low (or like if you machine the housing for a rotor pump into your sump) it probably won't matter since the pump inlet won't have to draw much head (*heehee*) to prime.

If you're comparing pumps you may want to see if the data sheets show the pressure head the pump can draw, or if there's someone you can ask.

Gear and rotor pumps also usually rely on pressurized delivery directed from the high pressure side of the pump to float the rotor inner and outer rings on an oil film within their housings, so you wouldn't want it running in frothy oil or being starved for oil like in a scavenge situation. I can snap a photo of a rotor pump housing if you want so you can see what I mean.

Gear and rotor pumps like to have liquid on the high pressure side at startup too, that'll help it prime, think of it like the pump has something to "push against" so like a loop of line, or reservoir mounted above the pump will help it prime at startup too.

Drew

[Mehul Botadra]

Check out Dailey Engineering.

[NickV]

I checked out dailey engineering, I think it is clear that would be a solution but if the gerotors work our solution of a custom housing completely within the engine is easier, simpler and lighter to implement (also cheaper). So I'm wondering if the gerotors work. I'm not having issues priming the scavenge pumps, more I might run into trouble when the gerotors are going at 6000 rpm. The concept of sliding vane pumps seems ok, but I haven't been able to find any at the size we might be interested in.

Thanks

[Jimmy01]

My experience with gerotors has been OK. They are used standard in Pace drysump pumps, and are also used as scavenge pumps in YZ/WR 450 engines so my assumption is that there is nothing fundamentally wrong with using them. We have had issues with frothy oil but I believe this is more due to poor drysump tank design rather than the pumps.

[Ockham]

The Dailey pump is the easiest solution out there. It's literally a bolt-on dry sump pump. I conversed with Lawrence Tech at FSAE West 2010 about their Dailey pump, and they use it mainly because it's reliable and simple. However, it's also very bulky and wicked heavy.

I'd rather not part with the CAD, but I made a custom mount for a two-rotor Pace Products C6 pump which worked well, and was much cheaper than the Dailey equivalent. Another disadvantage is that the Dailey uses -10AN inlet fittings, which need an awful lot of clearance, so you'll probably wind up mounting the engine higher than with a custom solution. I was biting my nails quite a bit last year, but the custom Pace mount with specially-made -6AN inlets let us place the engine very close to the ground with a 0.375in-thick oil pan.

The short version is that the Dailey will work, and you shouldn't have to worry about it. But cost and mass are its downsides.

Regarding your original question, the vast majority of dry sump systems use gerotor or Roots-type pumps. Cheaper versions will use gear pumps, but given that those aren't positive displacement, I say that's asking for trouble. Gerotors (and other positive displacement pumps) generally don't need to be mounted below the fluid they're pumping, but also aren't the best for high vacuum. AKA, they will draw some head, but how much depends on manufacturing precision. Generally, they draw more than enough for a low-mounted sump pump.