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aeration from scavenge pumps?

General engine tech -- Drag Racing to Circle Track

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dwilliams
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aeration from scavenge pumps?

Post by dwilliams » Thu Mar 26, 2020 4:00 am

Does anyone have any suggestions for sizing scavenge pumps vs. pressure pumps?

Most of the dry sump systems I've seen have a single pressure stage and three, four, or five scavenge stages, often the same size as the pressure stage. So the scavenge pumps are mostly churning air.

Is this contributing to oil aeration, or is it a non-issue?

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Re: aeration from scavenge pumps?

Post by Caprimaniac » Thu Mar 26, 2020 5:55 am

Doesn't the oil tank w/ baffles etc take care of the aeretion? So, when the pressure suck oil from the tank- if the tank has the necesarry de-aeration Devices, it will be- yes... de-aerated.

I have the impression that more than two scavenge stages are for roundy- round or roadracing; for instance 4 corners in roadracing. 3 on one side of pan in circles. And all stages large enough to suck out whatever volume in that corner. So, they have to be large. In a discussion one single scavange, I hear AN16 or most desireable AN20.

AN 12 on 3 or more scavange should be OK.
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Re: aeration from scavenge pumps?

Post by dannobee » Thu Mar 26, 2020 9:15 am

It's a non issue. There are baffles in the oil tank to combat aeration. And more stages can get you more crankcase vacuum, which generally gives you more power and better ring sealing.

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Re: aeration from scavenge pumps?

Post by Rick! » Thu Mar 26, 2020 11:19 am

https://www.drysump.com/index.php/technical-info

Seems like stated above, two scavenge stages are adequate for most applications.

When we were designing a dry sump system for a turbocharged 750 twingle, the target scavenge volume was around 4 engine volumes at 7500RPM or so. More scavenge made it tougher to de-aerate, less scavenge allowed oil vapors to condense in the intake system.

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Re: aeration from scavenge pumps?

Post by allencr267 » Thu Mar 26, 2020 4:13 pm

deleted
sorry

Walter R. Malik
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Re: aeration from scavenge pumps?

Post by Walter R. Malik » Thu Mar 26, 2020 5:37 pm

dwilliams wrote:
Thu Mar 26, 2020 4:00 am
Does anyone have any suggestions for sizing scavenge pumps vs. pressure pumps?

Most of the dry sump systems I've seen have a single pressure stage and three, four, or five scavenge stages, often the same size as the pressure stage. So the scavenge pumps are mostly churning air.

Is this contributing to oil aeration, or is it a non-issue?
I saw an interesting display at the last PRI show where several venues were using electric pumps for scavenging and just a single stage mechanical pump, on dry sump systems.
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Re: aeration from scavenge pumps?

Post by swampbuggy » Sat Mar 28, 2020 10:10 am

Good day Walter, Single stage mechanical pump....belt driven ?? Mark H.

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Re: aeration from scavenge pumps?

Post by Walter R. Malik » Sat Mar 28, 2020 11:03 am

swampbuggy wrote:
Sat Mar 28, 2020 10:10 am
Good day Walter, Single stage mechanical pump....belt driven ?? Mark H.
YEP ... I looked it up.
The company was "MATE-USA" using electric scavenging pumps from MARCO Automotive in Italy.
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Re: aeration from scavenge pumps?

Post by frnkeore » Sat Mar 28, 2020 1:47 pm

I'll add some of my thoughts, regarding dry sumps.

They have been in common use since at least WWII and are the best oiling system, for reciprocating engines. I ran Formula Atlantic for more than 5 years. They use a 1.6L Cosworth Ford engine, reving to 10.5K (I don't count the Toyota's they used for a time =; ) Those engines used a savage pump, 50% larger than the pressure pump, with a center pickup, -10 pickup and return. Pressure side, mounted pump to block. So, you can get by with that, comfortably. But, for V8's, it it's easier to use 2 stages for the return, one front and one back. The Open Comp car I sponsored, in the '80's, used 4 return stages, 3 in the pan and one in the right head, I consider that max but, you can mix and match stages. In gear pumps, the are 1.2 and 1.8 long pump gears (1.8 is from long ago memory) and you could make a 1.2 pressure x 1.8 return, for a simple dry sump system, then use a vacuum pump for drag racing.

Just as important, is the return system and the tank. The tank needs to be round, with a center pickup cone, -10 pickup (at least -8 pressure to block) and at least -12 return for SB V8's. There needs to be a Oberg screen (check them out if you don't know about them) in the return plumbing. It both catches fine engine particles and takes most of the air out of the return. You can use a regular filter but, you have to cut them open to check and the Oberg is reusable.

The tank needs to be round, at least 6" in diameter (6 x 16 = 8 Qt), to 10" and 10" to as much as 16" tall (add 1.5 - 2" for expansion and breathing, over the oil level) and then the filler and breather line. The return should come in from the side and dump on a perforated plate or replaceable screen. Oil level should be near the bottom of the screen and unless you create more that 3G's, that's all the baffle you need.

I also have a very well designed H&M SBF dry sump, from the mid '60's. They machined a pressure pump and savage pumps (2) that bolted to the stock location, inside the pan, chain driven from the crank, with only a single inlet and outlet, bulkhead fitting in the pan. All stages are the same, with non standard gear pumps, mounted inline with the crank.

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