Oil Pressure Problem or not?
 

I recently installed a Haltech in my FD and added a Bosch Temp/Oil pretty sensor. I noticed that once my car is warm and sitting at around 950rpm idle, my oil pressure is around 16-18psi. My tuner says this was low so I went and put an analog (Harbor Freight Oil Pressure Test Kit) gauge on to rule out a sensor issue. The analog gauge showed the same thing.

Here is the observed behavior of the pressure:

- At startup (like the minute I turn the key on a cold car) the PSI is roughly 100psi around 2.2k RPM but as the idle begins to drop within in a minute or so I see
- 1488RPM = 48psi
- 1380 RPM = 48psi
- 1238 RPM = 38 psi
- 975 RPM = 24psi
After the car continues to idle (5-7 minutes) and the oil gets warm, my RPM drops and I end up seeing the same thing my Bosch sensor shows which is around 16-18PSI at ~950RPM.

If I hold the throttle at 3k RPM, I see around 60psi or so which is above FSM spec. My pressure does rise with throttle so I dont think it's an issue with my pump.

I am running 10W-30 oil in my car but several people I've talked to suggested I put in 20W-50 so that's on my to-do list today. My tuner wants me to get to the bottom of this before and decide if im comfortable moving forward to the dyno. I guess the question is whether this is a new problem or not. I never had an oil pressure gauge on the car aside from OEM so I have no idea if my engine was always like this or not. I'll report back here after I put new oil in but would like any input this forum has to offer.

Your cold-startup pressure sounds normal, and hot idle oil pressures will be higher with new oil even if you stay with the same viscosity. The shop manual spec is 50 psi at 3,000 rpm when the engine is at normal operating temperature.

I use 10W-30 year round. It gets thinned out with raw gas, etc., over the winter because of cold starts and short trips. When that happens, the oil pressure at idle is noticeably lower than with fresh oil. Also, 1.2 quarts (1.7 quarts for the R1 or R2 model) of the thin, old oil remains in the lubrication system after changing the oil and filter. The idle oil pressure is also lower when the engine is hotter, as happens in stop-and-go traffic or spirited driving. If I keep the radiator fans running or the AC on in those situations, hot idle oil pressure doesn't get as low.

..

So are you saying my pressure is probably fine? I’m about to put 20w50 in. It was also suggested to me to put some Lucas Oil Stabilizer in as well.

My 10w30 probably only has 1000 miles on it. Maybe. But two days of that are track days.

That sounds low to me. My car's oil pressure (measured at a Banzai replacement filter pedestal) is around 30 psi at 1000 RPM, when the engine is warm (180 degF coolant and 190 degF oil). Oil pressure ramps up to 100psi by 3500 RPM and stays pretty flat at high RPM. This is with 20w50 oil, I haven't tried different weights since installing the oil pressure & temp sensors.

Does your stock gauge read in the normal range?
What is your oil temp?
What is your oil pressure higher than 3k rpm? and under boost?

The stock gauge does read normal range but I'm not sure anyone really trusts it. I just put in 20w50 +1/4 qt Lucas Oil Stabiler and I see what I think are much better numbers.

This screenshot is my data log from my Haltech. It's cold start to warm idle. Once the car settles around 1000rpm idle, the pressure is about 28-30psi. After I give it some 3-4krpm neutral pulls (this was all in my driveway), it settles to about 23psi. At 3k, it hits around 100psi or so. As for boost, I have not tested it yet. My tuner has been having me go through checks before we get the car on the dyno this Thursday. I has me limited to 3psi of boost right now so I can't go push harder if I wanted to.


https://cimg2.ibsrv.net/gimg/www.rx7...3f4af2e6dc.png

OE oil pressure gauge
 

That will read low if anything (usually blocked or mostly blocked sender internal orifice). I have never heard of one reading high. And especially with non-synthetic 10W30's, there can be a very large drop-off in hot viscosity above 200F which you will exceed if running hard.

If it were me, I'd do some research to see which 10W30's maintain their hot viscosity the best. You'll be surprised how much they vary. You may want to use a full synthetic for track days to maintain hot viscosity better.

Yeh. I don’t trust the OE one at all.

what did you do with the Thermowax pellet in the front pulley? if that thing stays open, oil pressure will be low everywhere. ~30psi at idle is basically find though, it doesn't need much pressure there

no idea. I’d have to ask my engine builder but it’s been a few years that he may not remember. That being said, I ran the latest numbers by him and he said I should be fine.

How did you calibrate the Haltech sensor? I.e. is it ready correctly....

using the corresponding calibration map for it. It’s a pretty well known sensor (Bosch pst-f1). I confirmed readings with an analog gauge

In general, a healthy engine should have 30psi at warm idle and 60psi at 3000 RPM. If you have that your oil pressure is fine and dandy.

Oil that is old and diluted with gas will drop oil pressure. That's why I always run 20w50 - as it thins with dilution it doesn't get TOO thin. I have seen a drop in oil pressure on my FD with old oil, especially after a bunch of hard driving.

All that said, the stock oil pressure sensor, when it is good, typically is accurate enough. Again, if you see around 30 at idle and 60 at 3k you are good. The oil pumps on these cars are super hardy and rarely if ever have problems. Typically the stock senders just read low over time.

If you do have low oil pressure unfortunately that's not fun to fix. There's typically nothing external that can be the problem - it's usually something under the front cover. Front cover O-ring, a plugged oil pickup, bad oil pickup gasket, and worst case bad bearings.

May be worth working with Rotorsports on this to double-check. Have them test oil pressure and also ask their advice since they built the engine.

This may just be a case of nothing but it's worth figuring out.

Dale

Bryan thinks we're good to go with the new readings after I moved to 20w50. That oil that's in there doesnt have a lot of miles on it but it does included 2 days at the track plus my dyno tune from last year so they weren't easy miles.

Duh, I kind of skipped the post with the data log and everything :). Yeah you are fine. SEND IT!

Missed you at DGRR this year! Got to meet APLScrambles though.

Dale

Def. plan to go next year! Heard you won a bunch of shirts!