How do you select a dry sump oil tank?

[John Fitzpatrick]

The ratios we're talking about relate to the fact that an inlet(s) will be uncovered periodically, and that stage will discharge foamy oil. Given that that's going to happen, how much larger do you make the tank to accommodate the foam and keep it out of the oil returned to the pressure stage. That's only indirectly related to the number of scavenge stages on the pump.

Some setups manifold the scavenge pumps into a single return line, others run a single line from each scavenge stage to the tank, but I have no idea why one gets used over the other or if that decision effects the size of the oil tank.

 

[Jac Mac]

For most systems with multiple scavenge stages [ 3 or more ] what is really reqd is an increase in size or number of the vent lines from dry sump tank to catch tank/breather tank to prevent pullover of oil with what would obviously be a larger amount of air movement, tank size itself should not really need to be increased as long as the system is well designed and the 2/3 oil-1/3 air ratios respected though common sense would suggest that to run say 4/5 scavenge sections into a 1gal 'air space' could create enough air flow/turbulence in that area to keep the oil in suspension and induce a problem.
Cost & weight are factors in the type/number of scavenge sections, if you have a system with say 4 scavenge sections or more then things would start to get very busy around the pump if they are all individually piped/plumbed, Same reason we are now seeing tailored pans with pumps attached direct.

 

[Randy V]

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.

After re-reading my post, I realized that i fat fingered my response which is not hard to do on an iPad with a virtual keyboard..

I meant to say:
You can pretty well bet that cars running the 24 hours of Lemans AREN'T out there with only 8 quarts of oil in them.

In the case of endurance races, it's also about reserve capacity to cover consumption and small leaks..