I've noticed that the NASCAR people generally use a 5 gallon oil tank while Sprint cars look like they're using something closer to half that. That started me wondering if there's a calculation or rule of thumb for deciding what the volume of the tank ought to be. Do you start with the volume normally used in a wet sump system, deduct for the difference in the volume of a dry sump versus wet sump oil pan, add in the amount held in the lines and cooler and come up with a figure that's an equivalent to the original wet sump, or do issues like race duration and governing body rules come into play?
How do you select a dry sump oil tank?
- Thread starter toy264
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Most manufacturers etc suggest 2/3 oil- 1/3 air for any given tank. Taller & smaller in dia is preferable to short & larger dia..... sooooo a 3 gall tank with 2 gals of oil plus whatever else in the system, cooler/filter/lines should be more than ample.
The sprint car setups are plenty for short races-sprints, only issue with many of those is some cannot be split for cleaning etc. Available space will dictate what you can run..
The sprint car setups are plenty for short races-sprints, only issue with many of those is some cannot be split for cleaning etc. Available space will dictate what you can run..
Terry Oxandale
Skinny Man
Good question, and one I wrestled with when I built my tanks. I think important aspects are how much oil remains wet in the pan (it shouldn't be much), and then how efficient is the separation of air from the oil while in the tank. I chose a minimum volume of 150% of what was normally carried in the OEM pan, and then designed the tank so that at 1.2 Gs of lateral or longitudinal force, the outlet port would remain covered in oil. Then to be safe I added another couple of quarts (9 quarts). Not scientific by any means. Jac mac's statement of a more narrow vertical tank allows less oil and still keep the outlet port covered, but how much air is in that oil if you go with too little volume to recover before being pulled back out of the tank?
Longest corner in seconds x 2 x volume of oil moved per second = minimum capacity of reservoir. There are some sanctioning bodies that dictate placement of the tank although I've not seen any restriction on capacity. There are considerations as well when looking at the type of events the car will run. You can pretty well bet that cars running the 24 hours of Lemans are out there with only 8 quarts of oil in them. Some people look at the temperature of the oil and figure that it will take 15 quarts a lot longer to heat up than 10. While that may be true, it's a flawed logic in my opinion.
My take on GTD dry sump oil tank, 548hp Gurney Weslake. The tank is filled with oil to the sill level, above that is a complex de-aeration screening. Before I get jumped on by Rons Rules, these pictures are for the benefit of the questions above, not any offer to sell such items. Frank
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I am doing some research on dry sump pans and most of the off the shelf units suit left or right hand turns. Pace build pans with a center trough which sort of ticks all the boxes, although they dont make a unit for the sbf I think I will fabricate something along these lines.
Bob
http://www.gt40s.com/forum/attachment.php?attachmentid=69782&stc=1&d=1390040611
Bob
http://www.gt40s.com/forum/attachment.php?attachmentid=69782&stc=1&d=1390040611
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Wouldn't a well-designed tank have a fill tube on a tangent? Just dumping in the oil from the top (as it appears to be the case here? Or am I just missing that?) doesn't start the de-aeration process very well.
The Peterson tanks, and all of the racing tanks I've seen all put the oil from the pump into the tank that way.
Even the swirl pot Wayne and I designed fills fuel from a tube on a tangent, and when tested with airy water was quite effective.
Will, you cannot see the many connections at the back of the tank, the pipe at the top is a breather for air outlet, you are correct in that the inlet pipe from the engine is indeed angled to the wall line, as it should be ! Frank
I have done a fair bit with hydraulics and I am surprised that the filter diffusers have not found their way into the world of automotive dry sump tanks. They are very effective at de foaming hydraulic oil and see no reason not to use one in an oil tank. They are also a filter trap so its a win win situation.
STAUFF:*Diffusers
Bob
STAUFF:*Diffusers
Bob
So it appears there is only one inlet? And the diffuser must be submerged in the tank?
From all I can see, it's obvious that one of the primary jobs of the tank is keep the air that the scavenging pumps add from reaching the high pressure pump stage, but I can't find anything empirical relating the size of the tank and the efficiency of the pump in doing that — beyond generalizations. In the interest of period correct: does anyone know who made the external oil pump Ford used back in the day and how they performed?
I'm starting to think it just might be easier to start with the assumption that in an ideal world, oil would be completely free of entrained air and then start adding fudge factors. But that just sounds lazy.
I'm starting to think it just might be easier to start with the assumption that in an ideal world, oil would be completely free of entrained air and then start adding fudge factors. But that just sounds lazy.
I'm starting to think it just might be easier to start with the assumption that in an ideal world, oil would be completely free of entrained air and then start adding fudge factors. But that just sounds lazy. [/QUOTE]
By its very nature scavenge pumps will always create air/foamed oil. To minimise this in an ideal world you would have sump shaped like a funnel, you would then have a single scavenge pump with just enough suction to cope with what the charge pump can fire at it. That in theory would not be sucking air. In the real world the engine is slung so low that a very shallow pan is used and depending on where you are on the track,uphill,downhill right,left and heavy braking will probably have all the oil going to one of the scavenge points in the sump. That leaves all the rest momentarily sucking air,multiply that by a 5 stage or more pump and that is a lot of air to get rid of.
Bob
By its very nature scavenge pumps will always create air/foamed oil. To minimise this in an ideal world you would have sump shaped like a funnel, you would then have a single scavenge pump with just enough suction to cope with what the charge pump can fire at it. That in theory would not be sucking air. In the real world the engine is slung so low that a very shallow pan is used and depending on where you are on the track,uphill,downhill right,left and heavy braking will probably have all the oil going to one of the scavenge points in the sump. That leaves all the rest momentarily sucking air,multiply that by a 5 stage or more pump and that is a lot of air to get rid of.
Bob
Jac mac-- Your 2:1 oil/air ratio for tank size implies some oil vol. to begin with. How would you start off figuring that?
Yes, I guess it does, but the answer is not so simple as there are many factors to take into consideration.
Lets think of your 289 for a start as an example with say the 3 gal tank mentioned & therefore 2 gals of oil in that tank.
Lets also assume that you have a 3 stage pump ( 1 pressure/2 scavenge ) plus a smallish oil cooler & std size ford filter & minimal oil line lengths. Once the system is primed & started & the motor has oil in all the right places that tank level might drop by say 1.5/2 quarts.... now in your 289 with a relatively short stroke you might be able to run safely at this lower level, that will depend on how much oil gets stacked away with windage @ hi-RPM, or rocker covers/ valley etc where the scavenge pump cannot reach it until you get on a straightaway.
Longer strokes & confined shallow oil pans increase the above issues, so you need more scavenge sections, deeper/larger pans & more oil capacity to match these, but with any race car weight is the enemy so less or just enough is best.
I think Randy mentioned earlier about how some people think running extra lube helps temp, again yes & no, it just takes longer to bring the larger amount up to temp & if the pan/scavenge system is not up to par that extra oil will just cause drag ( power loss) by way of windage.
The cooler should be able to keep the oil temp within a safe range, in perhaps your particular case you 'might' be able to run with a relatively small total amount of oil in the system, especially for shorter events, if your planning on endurance stuff tyhen you have to weigh up the cost in lap times of hauling an extra gallon around for the duration of the event versus perhaps having to pit for a top up if consumption rises.
Not to pin you down, but from that I'd think an "average" 289/302 3 stage with a well designed pan and 3 gallon tank would be reasonably safe running a 2-3 hour event keeping the RPM below 6,000, but 3-1/2 to 4 would be, I don't know, less daring?
Another thing that occurs to me is that a track with a lot of vertical curves could result in the scavenge inlets being uncovered and more air being drawn into the tank than on a flat track or oval. That true?
Another thing that occurs to me is that a track with a lot of vertical curves could result in the scavenge inlets being uncovered and more air being drawn into the tank than on a flat track or oval. That true?
Vertical curves- you mean flat corners with little to no camber/banking?- yes but longer high speed corners where you carry a lot of engine RPM are more likely to be an issue. Teretonga circuit in my area has a very long hi-speed sweeper that has been the undoing of many wet sump motors over the years.
Actually, I meant "bumps" when you get light in the seat for a second or so-- seen a lot in rallying. Something I have no intention of doing!
Dont the rally bashers call them 'yumps'?...You need to change to something like a 'Mustang', the only suitable vehicle for maintaining positive 'g' during those antics..
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Each section of the scavenge pump is bigger in capacity than the oil pump, so there will always be the same volume of air and oil being pumped back to the tank. It will just be different section of the pump thats pumping the air depending on track conditions. With three sections of scavenge pumps against one pressure pump its always going to be a third oil going back and two thirds air no matter what.
Bob
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