Oil pressure drop after small rev on idle

Hi Guys,

Im hoping someone can assist me with this as Im setting the oil pressure on my dry sump pump and have come across an issue which has me confused.

Im aiming for around 40psi oil pressure (FJ20 Turbo) at around 70C oil temp on idle. I set this however when I give the a slight rev the oil pressure then lowers when it comes back to idle to around 25-30 psi. I increased the pressure in the pump to 50 psi on idle ( after shutting down engine and making adjustment) then after a slight rev the pressure will then again drop to 25-30 psi when it comes back to idle... I did this again, increasing pressure on pump to around 55-60 psi when is starts but after a slight rev it seems to go back to 25-30 psi???

its a fresh build and the was dynod a couple of days ago with no issues occurring on the Dyno. On the way home after say 30 min of driving I noticed the oil temp has crept to 108C. Which is unheard of as I used to struggle to get oil to operating temp on the last build as I use a 12L dry sump tank. It has never been an issue before to the point I contemplated adding an oil heater to ensure correct oil temp. and now I have the total opposite.

Same oil, same engine, same pump, nothing has really changed.

what would cause this??

Engine?

dry sump loosing effectiveness?

oil has lost efficiency, (I only suggest this as oil temp rose to 108C on my drive home from tunning. and this was when the issue caught my eye in the logs)

Advice on how to proceed would be appreciated as I dont want to damage the engine if I am looking in the wrong area!

Hmm, some thoughts.

It seems the issue has developed, or at least been noticed, since the dyno' - it doesn't mean that's caused the issue but it is suggestive. Where is the oil cooler placed - between the scavenge pumps and the tank, or between the pressure stage and the engine? If the former, it's possible it's partially blocked by debris from the engine and/or scavenge pumps, if the latter it's possible it's less effective because of ail in the oil - neither may be the case, but something to consider.

With the oil pressure, does it recover if left idling to the set pressure, or does it stay low? What happens if it's held at a fast idle?

First things may be to check the oil tank level with the engine running, that it's baffle plate is in place, and that it's outlet is clear (it should have a mesh on it, too) - either could be allowing air into the oil to the pressure stage.

Next may be to check the various in-line filters and pickup meshes, including the one in the tank if not done with the above. There should be meshes on the sump pick-ups and in the tank, with at least one filter between the pressure stage and the engine with one between the scavenge stages and the tank that is easily inspected for potential developing problems very wise.

Next I'd suggest stripping and checking the pump assembly for damage and internal leakage.

Depending on what is, or isn't, found the next thing is to drop the sump and check the bearings of the B/Es and mains for damage.

Hi Gord,

Thanks for your response

I probably should have done more tests as you have suggested prior to posting.

In fact the issue occurred after adjusting the oil pressure the first time... I need to go back to the start oil pressure and see how it behaves. I am sure it would return to normal operation. It may be just set too low... I have inspected the the serviceable oil filter and the oil is clean and I'm certain it is not motor related.

The reason for reducing the oil pressure on the oil pump as I felt the oil pressure was a little high for cruising rpm, so . Which I feel contributes to the oil temp increasing whilst cruising for around 30 min. I don't run an oil cooler as in previous, the oil temp was too low and there was no need to an oil cooler in any season.

It may be the case that I will now need to add an oil cooler to the system and run the pump at a higher pressure previously set to achieve the desired result for cruising

Ok so i simply loosened the oil pressure setting a little too much. having played with the idle settings last night didnt help either.

I have now achieved my gaol which was to get the engine idle as low as possible smoothly 1100 -1150rpm (the lowest is has ever been) and maintain - 45psi at full temperature at idle (previously 55-65psi) and 90-100psi at full noise (previously 110-120psi).

Im hoping this would have also reduced my cruising oil pressure but i am yet to test a long cruise... Regardless the addition of an oil cooler i feel is required as this will assist with temp control, good thing is I have one ready for use ,but never bothered as was never needed.

Thanks Anyways