dry sump oil pressure

[Celica RA45]

what oil pressure should i be after at idle and also at max revs of 8800 rpm
At the moment have 250 klp at idle of 960 rpm and at 4000 have 600 klp cant take it higher yet as the new motor isnt run in as of yet

[off-road]

Rule of thumb is 10psi per 1000 rpm
Idiot light are about 15 psi so I guess anything better than about 20 psi is ok for idle.

[jeffro ra28]

80 psi when UNDER LOAD.
Standard for all race spec engines, Nascar use it, drag cars use, sprint cars use it, and japs use it as far as i know.
A "built" motor should hold atleast 50 psi at idle. If the setup is working properly and the releif valve is functioning well.

[gianttomato]

10 psi per 1000 rpm.

[jeffro ra28]

Are we saying we should have 10 psi at 1000rpm?

[gianttomato]

It's just a rule of thumb. I figure you'd run at least what a stockie would run at idle.

[jeffro ra28]

With all do respect, would a stockie run a dry sump? Perhaps so, but in most cases its going to be a purpose built motor.

I dont beleive in this rule of thumb to be truthful, oil pressure also has alot more to do with the load on the rotating parts. Say we are loading the engine heavily at 2000rpm and it has 20psi of oil pressure. If that was happening then id say its a recipe for disaster for any serious engine.

I tried to say that in such a way that i wasnt having a go

[love ke70]

well, i tried 5 psi at idle, and 2 psi at idle on hills for about 4000 km. was making 45psi at 3200.

cant say the bearings liked the idea too much when i pulled it down (was a fresh motor, with a rooted pump, im an idiot...)

so id say more than that as a starting point...

yes im subscribing for my own interest as much as im adding something helpful...

[clubagreenie]

What GT's saying is a dry sumo system would run at least what a road system does since theres no use in running less but will probably run more. Can it be an issue to have to much oil/pressure in reserve?

[love ke70]

well i know too much oil pressure can strip the soft metal off of bearings.

how much is too much?

[jeffro ra28]

I have run up to 100psi on the engine dyno. no problems. Engine was pulled down after 2 full race meetings without any drama's.

The only real debate here with to much oil pressure is when you are running hydraulic lifters. At high revs and high pressure (specially in rb25's) the oil bleeds from the lifters big time and fills up the head with oil, so much so it starts to spit out the breathers. So we use top end oil restrictors and a very large catch can.
Another point of interest is the volume of oil used. Some manufacturers get away with using massing amounts of volume but little pressure (5psi throughout). Namely i think, mercedes benz and rolls royce.

I have heard a fellow engine builder also say that high volume is bad because it doesnt allow the metal to dissapate its heat into the oil enough. Im still having some trouble getting my head around this, i think its BS.

[thechuckster]

i think that infers that if oil flow is too fast, it doesn't spend enough time in the cooler and hence does not assist as much in removing heat from bearing faces as it's too hot.


edit: but if the oil is sitting for longer in the reservoir and cooler (by way of much larger volume of oil in the system) then you would think that the argumetn is bogus.

Bill S. runs a dry sump in his race car - he'd be one to ask?

[jeffro ra28]

Not if you arent running an oil cooler tho.

[cambelt]

A lot of engines have a hot idle of only about 10 psi , most toyota oil light switches bring the light on at about 3 psi . A hot idle of 20 psi sounds like good bearing clearances.
It does depend on the viscosity of the oil tho .
Dave

[jeffro ra28]

a DRY sump tho, should hold well over 20 at idle. Thats using a belt driven, $1500 dry sump pump.

I built an rb25/30 with a n1 pump and its got 40psi at idle.....

The old holden 6 oil light is set at 6psi.....just an example.