How does oil pressure vary w/ RPM?

[Guest Anonymous]

I've never owned a car w/ an oil pressure gauge and I don't understand the relationship between oil pressure and RPM. When I goose it up to around 5k the oil pressure briefly (1-2 seconds) drops from around 2.0b to about 1.0-1.2b, before climbing up to around 2.5-3.0b. When the pressure dips like this, the oil warning light does not illuminate (although it does upon startup). When just tooling along at 3.5K to 4.0K the pressure is around 2.0b. Car is a 74 02 w/ s14 conversion. Can someone please help me to understand my observations? Thank you.

[Guest Anonymous]

You should have around 60lb at 3K. When cold the pressure can run up to 80-90lb at not too great an engine speed.

[Guest Anonymous]

2 psi at 3-4k rpm = lunched engine! A Bar is 1 atmosphere or just under 15 psi. Besides rpm, oil pressure can also vary according to the oil's viscosity (20w-50 will give higher pressure than 10w-30, for example) and the oil's temperature--it thins out as it heats up--why your gauge reads lower when the engine is hot vs cold. I've pegged my 150 psi gauge on a cold morning with 20w-50 oil...on a 200k mile engine at that!

Mike

[Guest Anonymous]

Your gauge is reading Bar which is equal to 14.7psi, your pump is driven directly by a chain attached to the crankshaft so the faster the engine the faster the pump and the higher the pressure, but so we don't blow the engine seals etc. apart the pressure is regulated to a maximum by a oil pressure relief valve, hence you can watch the engine from idle and as you rev. the pressure will increase and should come to a max.

When you accelerate quickly the pressure can drop through a few reasons mostly because of seepage in the pump, it has to have clearance between the moving parts, oil is heavy, so although the engine spins up quick it takes a few nano's for the pump to draw the oil, not unusual but if the pump is worn it will get worse and it can lead to serious trouble. If in doubt check with a professional, pumps are cheaper than engines.

Also with an S14 is it happening on bends (r/h bends normally) oil surge will bring the pump pickup out of the oil level.