Oil Pressure Observations - Anyone else using a gauge?
 

So I finally hooked up the control unit for my gauges and installed the oil pressure gauge in the block (via the plug between the intake and AC).

At idle, I get between 750-850 kPa (108-123 PSI). That seems kinda crazy high, but whatever...

It starts dropping as it warms up, eventually settling at about:
idle: 115 kPa (16.7 PSI)
3k: 400 kPA (58 PSI)
3.5k: 450-500 kPa (65.2-72.5 PSI)
4k: 525 kPa or so

It's fairly steady from there until ~7k RPM where it starts dropping, eventually down to around 425 kPA at/near redline. That's 61.4 PSI.

Having heard the whole 10 PSI per 1,000 RPM that seems a bit low.

Also, I am running a fairly large oil cooler (19 row) which can account for some pressure loss.

So would anyone be concerned with 61 PSI near redline? Not sure if a bigger or smaller cooler would help/hurt. No cooler would increase it of course so I'm somewhat curious what people are seeing stock. Maybe I'll bypass my cooler and see whenever I have some time.

I wouldn't be concerned with 61 psi at redline. I have heard that these boxers have crazy high initial oil pressures.

"Standard" WRX oil pressures: 100PSI cold/startup, 20-40PSI idle.

EDIT: This is 5W-30. Our cars on 0W-20 would see lower pressures overall I think.

What oil are you running?

I don't think that is anything to be worried about, but the fact that it starts to drop at the top end means people that up the rpm might have issues. I wonder if any tuners have looked at the oil pressure at their increased rpm.

Currently M1 0W-20 is in the car.

Sounds low.
I think location of the plug matters in these (IIRC the plugs on top of the block yield a bit lower readings, but only by few PSIs.

Details on the plug you used?

I thought about getting the reading just after the cooler also via another sandwich plate. I do have one laying around.

I get more than enough at idle and at around 6k I get 500 or so, it's just after 7k or so that it starts dropping, almost like cavitation in a water pump at high RPM.

^^ what he said. The sensor is very short and the oil pressure bounces around a bit in that location so I am questioning the sanity of putting the sender there.. just not sure it's the best spot. After the head is nice but I'm not exactly sure where in the oil gallery that plugs leads to.. right before it dumps back to the pan? If so I'd imagine lower pressures there...

It is low but not by a lot... the question how much lower does it fall if you raise the temp of the oil to 250-280F? Daily driven it's nothing to worry about but on track it could be or get to be too low.

You may consider running an 0w-30 or 5w-30 on track (like is suggested in your owners manual)

OR

Put a spring-shim in the oil pump to bring back up the oil pressure. I have an oil cooler on my race car and I have my oil pump shimmed to bring the pressures back up so I don't have to run thicker-than-necessary oil.

Hell 0W-20 is water at 150 degrees anyways :)

I have nothing against 0w-30/5w-30 though. I have 6 qts of RP 0w-20 I might have to swap out for 5w-30.

I think first I might try to switch the sensor location to see if I'm reading from a dump tube going into the pan. The reading might be just fine earlier in the system.. I have no idea where the oil galleries route in these non-hondas :) Pressure I would guess would be lower if this is coming from the end of the system (logically - no evidence of this).

I think you're reading from a correct location (misread what you were saying earlier), just past the pump, unless Subaru completely re-did their oiling for the FA engine.

Hmm that sucks. I was hoping it was at the end of the circuit :)

Under certain conditions the gauge bounces a bit so I was hoping that location wouldn't be ideal. I'll move it anyways, not going to hurt or take much time to do so. See what it reads just after the cooler. Could bypass the cooler too.

we will be logging pressures at the track this weekend with the stock system then put our overkill solution back on and relog to see how everything changes.

Dave, you are on the safe side

My observations:

I got my DEFI oil press\temp gauge installed recently

using stock fill 0W20

On a warmed engine (90С\190F oil) engine runs 1-0,9 bar \ 13-14 psi oil pressure

On the road the oil pressure seems to follow the tacho pretty fast and pretty straightforward in most cases - 2K rpm for 2bar \ 30psi , 3 for 3bar and so on till the bypass at 6 bar \ 87 psi sharp , no matter how you redline the engine

of course, when it's cold, the oil press could be higher


1 difference is I get steady 6bar under high load, no mater what

I will try these measures again when an oil cooler comes

I wish I had 87psi. A 26psi drop should not occur due to the cooler. Ugh. :(

correction - that's with Motul 300V 0W20

I recall stock fill didn't show that sharp 6bar performance when hot

which oil cooler do you use?

Mocal 19row 235 matrix with -10 AN lines.

On the race car it resulted in a net loss of about 2-3 PSI loss with at least twice the hose length, remote oil filter, 4 90 degree bends and 2 45s.

Current setup in the BRZ is that cooler, a total of ~4 feet of hose, 2 0 degree fittings (basically zero loss), 1 90 and 1 45.

Oh also.. I'm hoping to not take a nap after work tonight and hopefully will do the following testing:

Tonight: Install the gauge sender sandwich plate after the oil cooler sandwich plate, install oil pressure there (and temp, or I may just move temp over to the location the pressure is currently read from). If I don't put the temp in the current spot in the block I'll reinstall the OEM plug there.

Tomorrow night: Move the gauge sender sandwich plate between the spacer and oil cooler sandwich plate if possible (lines are exact length more or less but hopefully they'll move up 3/4"), otherwise, remove oil cooler sandwich plate and drain the cooler or loop the lines.

Possibly Friday/weekend, bypass cooler and test pressure sender in both locations again, although I suspect the tests above (plus original/current config) will show the same data as this test.

Does this car have one of those OEM oil to water cooler things? If so, getting rid of that would help- they have a pretty significant pressure drop.

And IMO you are measuring pressure in the right spot- right before the bearings.

I do not believe we have those.

No, OEM there is no oil cooler.

They do not have an oil to water cooler.

Have you taken measurements without the oil cooler in the loop? My search skills are failing me, but I can't find what pressures this vehicle should be running stock.

I haven't yet. I currently have the temp and pressure gauges in a second sandwich plate above the cooler sandwich plate. I didn't drive the car today but I'll probably drive it tomorrow and get some readings from that location, then I'll move it before the cooler which will show exactly what loss I'm getting from the cooler itself.

I can't wait to see Robi's testing... but here's some more data from this morning.


As noted above I switched both sensor locations and oil weight. Most of this increase is due to the oil weight I'm sure. However, the gauge is actually STABLE now instead of bouncing often in the original location.


It's still "cold" here (~60 degrees) but on the same route today I showed the following oil pressures at approx 75C oil temp (at the sandwich plate after the oil cooler):
3k: 650 kPa (94.3 PSI)
3.5k: 680 kPa (98.6 PSI)
4k: 715 kPa (103.7 PSI)
High RPM to redline: Rock solid at about 750 kPa (108.8 PSI)


That's a massive increase from before. Again I think the pressure increase is a combination of weather (colder temps and thus colder oil) and oil weight. The stability of the reading is, IMO, related to the location of the sensor but Robi will hopefully be able to provide his experiences this weekend.


Looking forward to tracking the car next weekend instead of worrying about oil pressure :)

Hi,

Am running a Greddy oil cooler with defi sensors on the greddy sandwich plate.

Oil pressure at idle is 1.5bar (around 21.8psi)

When car is started, oil pressure is at 7.5bar (108.8psi), which is pretty much the max. outside of track conditions.

Oil - Motul 0W20.

Hope the above info helps.

Cheers

I hv an oil cooler from Mishimoto.

Local weather noon time is about 32degC. Oil is TOTAL 5w50 full-syn.

Normal driving:
Oil temp reach 85 to 91DegC, the press is 1.5bar @ idle, Drive is ~ 6bar.

Track day:
Oil temp reach 116degC, the press is ~1.2bar @ idle, Drive is 6bar, but if went over 6000 rpm is ~ 5bar+.

if temp is about 100 to 109degC the press all the way hold 6 bar.

Q? should I used something like 15w50 for track day to gain the higher oil press, like keep it at min 6 bar with engine load?