Dry sump oil systems

[osubeaver]

For those of who run dry sump oil systems, what size oil line do you run? I have noticed that our car from last year has 3/4" ID on the oil feed and return and this seems a bit large, but I'm not sure. Also, what type of fittings do you use on your oil connections to your oil reservoir?

[osubeaver]

For those of who run dry sump oil systems, what size oil line do you run? I have noticed that our car from last year has 3/4" ID on the oil feed and return and this seems a bit large, but I'm not sure. Also, what type of fittings do you use on your oil connections to your oil reservoir?

[osubeaver]

bump

[Jackson]

Considering a Chevy 350 has a ~1/2" input on its oil pump, I think a 3/4" fitting may be a bit overkill for this situation.

I would probably just run 1/2" ID line everywhere. 3/8" would probably work too, especially if you have multiple pumps.

Get out your friction factor plots and see how much pressure drop you get at the flowrates you need. http://fsae.com/groupee_common/emoticons/icon_wink.gif (I know asking this question was a way to get around doing that, but I had to play the devils advocate)

Brian
Washington State FSAE

[Mark100]

Osubeaver,

Are you sure that the line is 3/4" ID? If it's an AN-12 line, it's not 3/4" ID. Also, if it's AN, none of them have a ID dimension that comes out to .750, as far as I can remember.

To just ask what size the hose should be without any other information is basically an open question. What is your flow rate through that pump, or your projected flow rate? Is the pump a scavenge pump or a pressure pump? Is the oil flow continous or intermitent?

The main concern you have in the low pressure / inlet lines, is that you don't drop the absolute pressure far enough that you get below the point where dissolved air (not the same as entrained air) will come out of solution. When the dissolved air comes out of solution it will become entrained air, and will drastically reduce the volumetric efficiency of your pump.

On our car, we ran a pressure pump that had a higher volume capacity than the stock pump. The design criterion (suggested by a professional) and from looking at some old WW2 SAE papers, was to keep the velocity in the inlet to 5-6 ft/s or below. This was to reduce the chance of having dissolved air come out of solution. I wanted to put some pressure sensors on the inlet lines to see what the absolute pressure was, but never around to it. That would be the ideal way to verify that you have your line sized correctly. Can't remember what the suggested pressure to stay above is, but I think it's around 2-4 psia.

The scavenge lines inlet sizes CAN be smaller if you want to, as they are already pulling in air with entrained air, and the volumetric efficiency will be lower than the pressure pump. With our system, the scavenge pumps had a higher theoretical volumetric capacity, but obviously VE would be reduced, and they are pumping oil and air, plus for ease of manufacturing, we kept all sections the same inlet size.

Generaly rule of thumb for outlet lines is to keep oil velocity below 25ft/s. We ran -12 on the inlets (.484" on the inlets) and -8 (can't remember ID) on the outlets. Probably could have gone to -10 on the inlets to the scavenge pumps, but didn't for ease of manufacturing.

Hope that helps.

[osubeaver]

Thanks for the info. The problem is that I did not design the dry sump, and the guy who did is gone and did not leave much information behind as to his calculations and such. I do know that we run 2 pumps though. As for the hose, I don't believe it is an AN size. I think it is just 3/4" ID. I notice that you say -12 is .484", but I'm looking at the russel performance catalog and they list -12 as having an actual I.D. of 11/16" (.6875").

[Mark100]

Your right, the ID for an AN-12 fitting is bigger than .484". I'm getting old and senile at my age, and my memory plays tricks on an old guy like myself. I'm getting old and senile at my age, and my memory plays tricks on an old guy like myself.

AN-12 is however, also not .6875" ID. AN-12 fittings have an ID of .608-.610".

You have to measure an actual fitting to get the real ID. The will be the same across companies though. XRP, Earl's (a.k.a. dog shit), and Aeroquip will all be the same ID. You can go into ProE and look at the parts libraries and they will have the fittings in there. The models (and thus the ID's) are fairly accurate.

Here's what I looked up from my numbers that I had.
AN-12 .610"
AN-10 .484"
AN-8 .391"

Hope that clears things up. Sorry about that.

[Mark100]

Osubeaver,

If you don't mind giving the numbers out, what is the pump width, the volume pumped per rev, and the revs the pump is turning at? Or just the theoretical volumetric flow. If you have only two pumps, I'm betting that 3/4 ID hose is very reasonable, and not too large at all. I would think talking to the guy that designed the system would also be the best place to start with basic questions. Just my $.02. Later.

[osubeaver]

I will post those numbers if I can track down the guy who designed it, but they may be difficult. I think he may have graduated and moved on.

Mark100,

Thanks for the heads up on the AN sizes. I figured what they had printed in the catolog is all I needed to know. I do have to ask, however, why you say Earl's is dog shit. I personally haven't ever used any Earl's products, but I was under the impression that they were pretty good.

[Mark100]

Earl's is decent, but it's more that there quality control is rather lacking. I have bought plenty of AN plumbing fittins ranging from -2 to -12. I have seen two AN-12 (Earl's) hose ends that had poorly cut threads, that were basically cross threaded. These were new out of the package hose ends. There was anodizing on the messed up threads, so it wasn't a return. I have seen one bad -10 hose end, too. We have also had a -12 hose end that would not swivel at all -totally seized. Also the swivel hose ends from Earl's only swivel or turn if you man handle them. Aeroquip swivel hose ends, spin very easily - because the construction of the hose end is different.

Also I have waited months for Earl's servishop (one at Indy) to get me my parts. And, while less of a big deal, I have received some -4 and -6 unions that had horrible anodizing. I also had a quickrelease hose end come with no seal in it. Like I said, most of it is bad QA, but still aeroquip stuff is nicer. While fittings can be taken back, I expect quality and time is at a premium when in a FSAE project.

However, I do think that the Earl's lightweight hose is much nicer to work with and doesn't have as much a tendency to pinch as the Aeroquip startlite hose. Aeroquip fittings on Earl's lightweight hose (called Prolite or something like that). Earl's also has a better selction of speed-seal (teflon hose) fittings, and other oddball adapters. Although XRP is good, too. It's nice to have a mix of hose ends around, too, as some things like how far a hose end sticks out, for the same bend angle, is different from Aeroquip to Earl's.