Calculating oil pump requirements

[buzzinhalfdozen]

I'm pretty sure I've got too much oil pump on my engine (dry sump) is there a way of figuring out exactly how much pump you need? Would you use total bearing area or another method? Or am I simply trying to find an answer that doesn't exist? Thanks Joe

[FED 387]

Joe--- I was told by a friend who is a mechanical engineer that the way an engineer calculates an engines requirements is to find the total surface area in the engine that needs to be lubricated , the thickness of the film you want, the replenishing rate you will need to maintain a cool steady supply of lubricant usually measured in GPM(gallons per minute)-- you then need to calculate the space need for the pump and the area ofthe pan. Its a complex set of calcu;ations--- quite simply I would call Tech @ Serdi/Peterson/Weaver see what these guys say--- Generally the amount of pressure in a hot engine with hot oil at idle should be sufficient to lubricate a drag engine at speeds less than about 8500 rpm----FED 387

[buzzinhalfdozen]

Thanks for the reply, yeah I figured there was more to it than I thought. I did speak to Peterson about a pump a couple years ago but he asked what my GPH requirement was you can guess my reply. Being as most of my oil is contained in the tank I thought maybe that would make it simpler. I suppose another call can't hurt, maybe it's not even worth the effort but it seems like it would be considering the load that seems to be on the pump when I oil prime it. Thanks again Joe

[FED 387]

Joe--- pump gear ratio determines how fast the pump is turning you don't need crazy RPMS I think the absolute pump max should turn like 57% of engine speed usually lots lower than that probably like 1/3 of engine speed and usually there is an adjustment on the pump to increase or decrease the pressure--- you only need so much to make it work and since the pump is belt driven we are talking HORSEPOWER here maybe as much as 15HP if ya got it all wrong. You definitely need to talk around see what these pump guys recommend. Just remember that the oil gets sucked out of the pan into the tank and then along with the help of gravity feed gets sucked out of the tank thru a little bitty hose to the pump to be dispersed thru out the engine ---That sucking/pumping takes a lot of power (horsepower) to run the pump. I'll bet you could get away with maybe around 30 pounds pressure to lube your engine ya really don't need 70-100 pounds. It'll be high when the oil is cold but as it warms up it'll come down to where you want it.---Just remember pressure and volume are not the same thing you can have lots pressure and very little oil actually moving thru the system conversely you can have lots volume and very little pressure. You need to have everything sized correctly( Hoses/ fittings/Bends in the hose etc)

[SSDiv6]

Originally Posted by buzzinhalfdozen

I'm pretty sure I've got too much oil pump on my engine (dry sump) is there a way of figuring out exactly how much pump you need? Would you use total bearing area or another method? Or am I simply trying to find an answer that doesn't exist? Thanks Joe

Could you elaborate what do you mean by too much oil?

[tj310]

Too much oil 'pressure' would force the pressure release valve open . Too much oil would be excessive clearances. I remember running a circle track motor I couldn't keep oil pressure, switched to a dry sump problem solved. ---Trevor

[buzzinhalfdozen]

Originally Posted by SSDiv6

Could you elaborate what do you mean by too much oil?

SSDiv6 Too much oil pump, Pumps more oil GPH than engine requirements. FED 387, I'm running the pump @ 45% engine speed, yes I'm aware of the adjustable pressure regulator, set @ 50 PSI cold, really never loses any pressure. Problem with (in my mind) slowing the pump more is I'm also slowing the scavenge stages, maybe it's not an issue I don't know or maybe I need a smaller pump section and keep the current scavenge, I'm certainly no expert on this hence the questions. Thanks for all the replies. Joe

[SSDiv6]

Originally Posted by buzzinhalfdozen

SSDiv6 Too much oil pump, Pumps more oil GPH than engine requirements. FED 387, I'm running the pump @ 45% engine speed, yes I'm aware of the adjustable pressure regulator, set @ 50 PSI cold, really never loses any pressure. Problem with (in my mind) slowing the pump more is I'm also slowing the scavenge stages, maybe it's not an issue I don't know or maybe I need a smaller pump section and keep the current scavenge, I'm certainly no expert on this hence the questions. Thanks for all the replies. Joe

Joe,
If you are still running the V-6 engine, like you stated, you may need a smaller pump.

[buzzinhalfdozen]

Yeah still trying with the V6 stuff, agreed I believe my pump is too large. Think I'll try on of the pump companies again and see what they'll recommend. Thanks Joe

[Ed Wright]

It would be slick if you could run a factory pump at a constant speed with n electric motor to measure how long it takes to pump a quart, or whatever. Do they rate them in gallon an hour, like a fuel pump? (I'm thinking not) Then do the same with your dry sump pump. Might be a trick to get an electric motor to run at a constant RPM with both pumps. May be easier to do it off a gasoline engine. It would be interesting to know if shortening the housing and impeller 10% would get a 10% drop in volume pumped.

During the 1980s I ran an "outlaw" sprint car on dirt, (didn't drive it, you can hire crazy people for that) with a Peterson dry sump set up. I felt like it was way more pump than I needed. Never did play with that, making enough power was never an issue. Always wondered about that pump. I'm sure it was over-kill in size to cover their tails.