Yesterday i was driving in scorching weather (32°C / 90°F) and after around 15 Minutes of relaxed driving, when the oil reached around 105°C / 221°F i noticed the oil pressure was dropping when standing and idling (crossings, traffic lights, etc). Idle RPM was normal but the gauge showed between 0.5 - 0.7 bar / 7.25 - 10 psi.
I am sure this is not a normal oil pressure for a rotary, it most certainly isn't for a piston engine. The oil pressure was normal once i just touched the gas lightly (1000-1100 rpm) and sometimes after standing for around 15 seconds the oil pressure would go to 1.0 - 1.1 bar / 14.5 - 16 psi again - which i would consider normal. Oil level was right on the edge to F on the dipstick.

I am running a mostly stock engine, rebuilt 10.000 kms / 6.000 mls and 5 years ago, compression in april was between 110 and 115 (corrected) on 31st of march.
Stock twins, even if the return line of the rear one is leaking they are both working (until they hopefully get thrown out for a single soon)
Most emissions stuff is removed
Oil Pump takes 2T oil from a seperate tank and i add in a small gulp of 2T in each full tank.
Engine Oil is Liqui Molly 10W-60, last oil change was a month ago including a new filter of course.

I could imagine it being an issue with the sensor, which would be of course my preferred outcome - for that i would have to find it however...
If anyone else has ideas and suggestions, let me know, i am happy for any ideas that could bring me to fixing this issue

 

If you are going off the factory gauge. That's not going to be accurate at all, especially in the lower rpms/pressures. For a true reading you need a quality aftermarket gauge.

Many of the factory Oil pressure gauges don't work at all, or work off and on, especially in the idle ranges. My factory one is currenty doing this. Sometimes its a bad sender, sometimes its build up in the sender port etc.

 

My bad, i missed important information: I don‘t use the factory gauge but an aftermarket one (Prosport i think). However i don‘t know yet where and theough which sensor it gets the pressure.
i will try to locate the sensor tomorrow.

 

2 things.....

First, your oil temps should not be that high. You either need to upgrade your coolers or go to a heavier weight oil.

Second, the fsm shows how to check oil pressure and there was minor discussion on it some time ago. If i remember right, the pressure reading is to be checked at 3000rpm. If its above whatever value stated in the fsm then it passes. It makes no mention of idle or any other condition...... or something like that

Since your temps are WAY too high, naturally oil pressure will be lower. Your car requires corrective action with either heavier oil or an oil cooler upgrade.

 

~60 psi at 3K RPM

 

If. Your oil pan is dented up, It could be pressing against the oil uptake strainer.

P.s. oil should only be filled to half way up the hatch/hash marks on the dipstick.

 

Restriction at the strainer would affect high RPM pressure more than idle pressure...the oil intake flow at idle is much less than at high RPM, and, of course, that's why idle oil pressure is always lower.

 

What would be a good oil temp? I would have expected 100-105 to be ok in hot weather. Since i already use 10W60 i am sure i should not go any heavier.
I am not sure if my car has the stock oil coolers... any way to easily verify this?
Maybe the car just needs another oil change to flush through... old oil was pitch black when it came out, despite being only 1,5 years and 1000km old.

I guess when warm? I will check that when i have time.

Oil pan is fine as far as i can tell. Than i misread; found info saying to fill up right below full. However i don't think this will do harm to the engine and should not lead to low pressure.

 

Yes, when warm. Cold oil pressure often can exceed 100 psi depending on oil viscosity.

 

You should be cycling between ~170-195. You shouldn't be seeing 200+ at all under street conditions.

 

I've measured oil temp and pressure in my mostly-stock FD, I've seen around 25psi at 900 RPM idle and 104 degC oil temp which is pretty close to 220F. When the engine speed briefly dipped to 750 RPM when creeping the car around slowly, oil pressure went down to 15-20psi. That 104 degC oil temp is measured at the oil filter pedestal, and my RX7 is a base model with single stock oil cooler. I'm planning to upgrade the oil cooling eventually, but the car has ran OK for dozens of years in this form before I started measuring oil temp and pressure.
More details here: https://www.rx7club.com/3rd-generati...alogs-1170689/

If you have an air compressor, one way to test the sensor is to remove it from the engine and pressurize it with regulated air from an air compressor.