Oil pressure readings!
 

I know this is been discussed many times but i cant find the answer that im looking for.
The issue I have is that i installed a cpts sensor at the OEM oil gauge sender position and the readings i get on my loggings are kind of low and will like to know if its the position of the sender the problem.

The car is single turbo with OMP delete and double greddy oil coolers. The readings i get is oil pressure at cruising 60-70 psi 40-50 idle and when on boost it starts to drop. My temperatures are at the top 140-160 degrees if in traffic and drop to 120-130 when the car cruises.

The specs are in the shop manual for what is good/normal

That really sounds fine. In general if you have 30 psi at idle and 60 psi at 3000 RPM minimum you are doing good.

Dale

IIRC 50 psi @ 3k rpm is minimum in the FSM. You’ll probably see oil pressure readings highest at cold start-up with fresh oil and then over time they’ll slowly start to drop a bit on cold start with a bit of fuel dilution…which IMO is kind of normal for a rotary.
Oil temps sound fine, but I’ve never monitored mine.

I think im a bit low on oil pressure the temperature i know its because i dont use a thermostat but the pressure is on the low side because on WOT it drops down to 50 psi, but its totally normal on idle and 3000 rpm.

Edit

Did you leave the shaft in the front cover when you eliminated the OMP? I have seen multiple engine failures from people removing the shaft and not blocking the supply passage, causing oil to blow by into the cover.

I have also seen where the oil pump set screw works its way into the pump and ends up sitting inside the oil pick up tube. This allows the center section of the pump to rotate.

https://cimg8.ibsrv.net/gimg/www.rx7...2f5bdfea8a.jpg

No just removed the OMP and used one off your own blocking plates and the injector plugs nothing else.

Great. Was the engine rebuilt?

Yes its a street ported rebuild

Then there is the possibility that the woodruff key on the oil pump was pushed out when the gear was installed.

But wouldnt it affect the idle pressure or the cruising?

There is a nut and washer holding the gear on the pump, but the key stops the gear from slipping on the pump shaft. I am just giving you possible issues that would cause your described problem. These are all things I seen in the decades I have been rebuilding engines.

I have an aftermarket oil pressure sensor and oil temperature on my car, the readings get datalogged by my aftermarket ECU. Both sensors are mounted in a Banzai aftermarket oil filter pedestal. This screenshot shows pressure vs RPM, the blue dots are when the oil is cold and red dots are when the oil is warm. This is 20w50 oil on a stock engine with single stock oil cooler (base model), I don't know the exact mileage but I've put about 20k miles on it. It was a used JDM pullout engine from a 1996-1998 car based on the engine harness and turbos that came with it, so I'm guessing at least 50k miles on the engine total. Oil pressure is higher when the oil is cold, and lower when the oil is warm. I haven't noticed different readings for high boost or low boost, pressure seems to depend mostly on engine speed and oil temperature.

https://cimg5.ibsrv.net/gimg/www.rx7...2e318f6725.png

On my loggings i go about 85psi to 4000rpm and then always dips exactly at 4000 rpm about 15-20 psi.

Thanks guys will check everything again and see what the problem is.

Hey guys changed my oil pan because it had a dent in it because someone had the same issue with oil pressure dipping over 4000 rpm and it was his oil pan that was dented.
Changing the oil pan got rid of the 4000 rpm dip but other issues showed on my ecu logging now.
First of all i had my pressure sensor hooked up on the line out from the engine before the oil cooler and it was reading good at cruising speeds around 50-80 psi depending on engine speed, during wot i was seing pressures rising at 150 psi droping down to 70 psi rising up again, changed my sensor location and installing it on my oil pedestal which changed to 120 psi and droping to 70 psi up and down.
i dont know what this issue is now im really confused.
One thing im considering is that my oil pressure is to high forcing my relief valve opening and losing pressure and the closing bulding pressure up again?
I even seen my oil pressure droping to 6 psi on decelaration.

That sounds wild, I'm not sure how long an engine would survive with 6psi of oil pressure. If you can share ECU datalogs or screenshots, I would be interested to take a look.

Screenshot from a recent datalog below, this is my car running through second and third gear. This is pretty fresh 20w50 oil, I changed the oil about 20 miles ago. The oil pressure sensor is mounted in the oil filter housing. I do see a slight dip or plateau, but the high numbers are 101-104psi at 4000-5000 RPM and the low numbers are 96-97psi at 7000 RPM. The pressure appears to be pretty consistently related to engine speed, not throttle or engine load. In other words, about 100psi at 5000 RPM when accelerating and about 100psi at 5000 RPM when decelerating. The lowest reading in this screenshot is 27 psi at 875 RPM.

https://cimg4.ibsrv.net/gimg/www.rx7...fa1a726602.png

Is it possible that during decel the oil pump pickup is being exposed to air?

https://cimg6.ibsrv.net/gimg/www.rx7...4bb2896201.png
Most probably figured out what the problem is. Since i have two Greddy oil coolers and using 10w45 oil with no oil thermostat and ambient temps close to 25 celcius my oil temp reaches top 73 celcius which causes high oil pressures forcing my relief valve opening and closing causing the eratic oil pressures on my logging.
The only thing i cant figure out is why it dropped to 6 psi on decelerate.

Not possible just had a new oil change

not possible just had a new oil change

I find it hard to believe that the relief valves would overcompensate so much that the pressure drops from 120psi to 20psi or lower, unless yours are modified or damaged and not working properly. Generally those sort of bypass valves are spring loaded and often working in a 'partially open' state so they relieve just enough flow to keep the pressure stable.


Can you zoom in closer to the dropouts? For instance, I would zoom in to view just 5:00-5:30 in the log, or just 10:20-10:50 in the log. Have you seen any other sensors dropping out or jumping to unrealistic readings near the same time? If so, that could be an electrical problem or harness problem resulting in bad sensor readings.

https://cimg7.ibsrv.net/gimg/www.rx7...114f268012.png
https://cimg7.ibsrv.net/gimg/www.rx7...7a02c0df23.png
No no other sensor dropouts at the same time.