is it the higher the engine temp, the higher the oil pressure relatively and vice versa?

Thanks

 

No. Oil pressure is set by the oil pressure regulator.

 

so oil pressure is independent from engine temp.
but i heard someone said engine oil is also used for cooling in rotary? so i was thinking if you run your car under a hotter weather then the engine needs more oil for cooling effect thus higher oil pressure.

sorry for newbie question.

 

So I'm going to assume that as the viscosity changes, the oil pressure regulator "compensates". Is this correct?

 

I know that with other cars, like my bros firebird or my freinds supra; as the engine heats up, oill pressure goes down. The viscosity does change with heat.

I cant remember what my 7 did since I havent driven it in so long

 

I know the viscosity changes. I meant, does that change affect oil pressure (in a RX7)?

 

pressure does drop a bit when the engine is warmed up.

 

Ok, then I don't understand Aaron's statement.

Paraphrased

r33- Does temperature affect oil pressure?

Aaron- No, it's controlled by the oil pressure regulator.

snowball- Yes, pressure does drop.

Confused...

 

Ok, cold thick oil takes more pressure to flow the same amount through a given passage; whats easier to drink through a straw? A milkshake or just milk? But since its regulated, im guessing that excess pressure is bled off through the regulator. This would mean when the oil temprature is cold, there is less oil getting to the places that need it since the regulator is just bleading it off.

 

Maybe you are thinking of the temperature pressure relationship in a closed system. It is true that in a closed system if temp increases, pressure will also increase. Your 13B is not a closed system, so any increase in oil pressure is allowed to transfer its energy to atmosphere. As temperature increases, the absolute or dynamic viscosity drops. Kinematic viscosity is the viscosity given to you on the label of the oil. It is related to dynamic viscosity by the inverse of the oils density. It is the density that changes with temperature, which brings about the change in dynamic viscosity. As temperature increases, density drops, and the shear stress between fluid layers decreases making it easier for the oil to flow. This should mean that the oil pressure sensor would show you a decrease in pressure. This should be a small decrease that comes about by an increase in flow efficiency of the oil. But like aaron said, its the oil pressure regulator that regulates oil pressure.

 

As the oil thins as the engine warms, pressure does drop a bit. However above 3000 RPM or so the pressure regulator is bypassing oil back into the pan so pressure above that level is supposed to be constant and controlled by the regulator.

Idle pressure is lower since the oil pump is spinning slower. Thicker oils can make that pressure higher but generally the regulator will keep the pressure constant at higher engine speeds.

 

Ok, that's what I was thinking. Thanks for clarifying.

 

so as what Aaron says, oil pressure is not proportional to rpm once it goes beyong 3k rpm?
correct me if i m wrong

 

hey am having kinda the same problem but when my car is just sitting there how high your oil preasure supposed to be

 

mine sits below the first line is that bad or good

 

^my oil pressure is 40-45 at idle

 

Once the oil pressure has reached maximum (according to the FSM this is around 3000 RPM) then the regulator starts to bypass and keep the pressure at a set value.

Oil pressure below the low mark probably means a bad sender.