Observed Oil Pressure with a gauge
 

As the title says. There has been a lot of talk on oil pressure lately. So the more info we can get. The better informed we will be. So post up. The more info, the better.

Gauge - SpeedHut 0 to 150 psi.
Sensor location - Tee'd with the factory sensor. Different location will give different reading.
Oil - Mobil 1 0w40. Different weight oil may give a different reading.
Oil Cooler - Z1 34 row.
Oil Temp when warm - 180F.
Engine temp when warm - 185F.

These are are the oil pressures at different rpms that I observed. Using 3rd gear. Giving the throttle just enough to get to the rpm and hold it there for about one minute.

Cold Start - 65F outside temp. 104 psi dropping to 48 psi after about 3 minutes
Cold Start - 82F outside temp. 93psi dropping to 48 psi after about 3 minutes.
Warm Idle - 38 psi
2,000 rpm - 75 psi
3,000 rpm - 87 psi
4,000 rpm - 93 psi
5,000 rpm - Goes to 102 psi then drops to 93 psi
6,000 rpm - Goes to 104 psi then drops to 93 psi
7,000 rpm - Goes to 105 psi then drops to 93 psi
7,500 rpm - Goes to 105 psi then drops to 92 psi

Here's my input:

Gauge: Defi Red Racer 0 - 1,000 kPa (0 - 140 psi)
Sensor Location: On oil filter sandwich adapter plate (non-thermostatic)
Oil Cooler: None
Oil: Nissan Genuine Ester Oil 5W-30

Cold start - ambient temp. 27C (80F)
Initial reading: 760 kPa (108 psi)
After 1 minute: 500 kPa (71 psi)
After 2 minutes: 390 kPa (56 psi)
After 3 minutes: 340 kPa (49 psi)

Oil temp. 80C (180F)
Idle (no load): 190 kPa (27 psi)
1000 rpm (no load): 270 kPa (39 psi)
2000 rpm (no load): 440 kPa (63 psi)
3000 rpm (no load): 700 kPa (100 psi)

Oil temp. 92C (198F)
Idle (no load): 140 kPa (20 psi)
2000 rpm (3rd gear): 380 kPa (54 psi)
3000 rpm (3rd gear): 600 kPa (86 psi)

FYI: FSM lists oil pressure specs as follows:
Oil temp. 80C (180F)
Idle (no load): more than 98 kPa (14 psi)
2000 rpm (no load): more than 294 kPa (42 psi)

This is a great idea! I will add my results in a few days.

If your pressure sensor mounts in a sandwich plate, you are measuring the oil pressure going INTO the oil filter. This reading will be higher than the actual engine oil pressure, since it takes some pressure to push the oil through the filter.

If your pressure sensor is mounted in the factory location, you are measuring the oil pressure AFTER the oil filter.

On a future episode MotorvateDIY Garage, we will show how much pressure it takes to push oil through the oil filter.

Sub'd.

I should have something to add once my adapter fittings for my pressure sensor arrive.

Interesting. I can only share my experience. Initially, I installed an AEM oil pressure gauge (0-150 psi) based on a DIY posted by Spearfish some time ago. I removed the factory sensor and replaced it with the AEM sensor (I didn't bother installing a tee fitting to accommodate both sensors). With that set-up, I would see a reading of about 90-100 psi on a cold start, which dropped rapidly as indicated above by Rusty. At operating temperature (200F), I would see a reading of 18-20 psi at idle (no load). I can't recall exactly what the readings were under load at operating temperature, but they varied from about 70-85 psi at 2,500 to 3,000 rpm in 6th gear. I was running Motul 8100 X-Clean 5W-30 at the time. The next year, I switched to the Defi Red Racer Gauge (see above) since I preferred its appearance and it seemed to be more reliable. I re-installed the factory sensor in its original location and installed the Defi sensor on the oil filter sandwich plate (see above). I continued to run with the Motul oil (... only switched to the Nissan Ester oil at my last oil change when I took the readings shown in my earlier post). Anyway, I didn't notice any remarkable difference in readings after switching the sensor location. In fact, the readings remained virtually unchanged. I still continued to see a reading of 20 psi at idle under no load at operating temperature (200F).

I see a red light with the engine off and no light at everything else :).

Seriously, I have a 150# gauge that I need to install on the A Pillar, so at least now I know what I should expect to see.

This is a great thread..

Did you get any DTC / dummy light when you were running without the OEM pressure switch?

No.

This is interesting. I've been putting some effort into trying to maintain the stock pressure switch (waiting on the T-fittings is why it's not done yet). If I can just delete the OEM switch and put the defi sender into the hole (with a BSP->NPT adapter), it will save me some headache. I'll also sleep a little better at night without worrying about two sensors hanging off of a tee, bouncing around on the highway. Thanks for sharing that.

What was the reason for moving from the factory location to the sandwich plate?

There is no issues with installing a tee. The only thing you have to worry about is how you clock it to position the sensor. :tup:

I understand many people have used tees with no problem, but I tend to worry unnecessarily about things. It's one of my personality flaws that I've learned to live with :icon14:

I don't like the "Tee" fittings either. I worry if the belt breaks, it could snap the oil off pressure sensor.

Here is a preview of a future episode "Making an Inexpensive OLED Oil Pressure Gauge"
It uses an Arduino Uno clone, 128x32 OLED display and a 150 PSI digital pressure sensor.

http://www.the370z.com/attachment.ph...1&d=1535463663

Two reasons:
First, I was looking for some redundancy. By re-installing the factory sensor, I had some back-up in the event that the Defi sensor/gauge ever malfunctioned. It was for ease of mind.
Second, the Defi sensor is configured such that it can't be installed using a socket (standard and/or deep). It becomes obvious why once you have it in your hand. And, I found that there wasn't enough room to tighten it into the factory port using a standard open-ended wrench. You might be able to install it using a crow-foot wrench ... but I opted instead to simply purchase an oil filter sandwich plate and install the sensor in one of the ports in the plate. I had to purchase an adapter since the female port thread was 1/8 NPT and the male sensor thread was 1/8 BSP (i.e., the Defi sensor thread is metric).

That's cool; I like the redundancy. Ideally I'd like to run a separate sandwich plate for the sensors, but with the combination of the Z1 cooler sandwich plate and the oem oil/water "cooler", I don't think I'll have enough room left for the filter (and I don't want to relocate at this point)

It's interesting that your Defi gauge is 1/8 BSP; which do you have? I have the Defi BF Advance, and the manual is saying it's 1/8 NPT.

Well, the acronyms used for pipe threads certainly can be confusing. The install manual for my Defi Racer gauge indicated that the threads on the sensor were 1/8 PT ... which is a Japanese Industrial Standard (JIS) designation. After researching the different thread types and designations, I discovered that the 1/8 PT thread was equivalent to and interchangeable with 1/8 BSPT. So, you don't need an adapter if you intend to install the Defi sensor directly into the factory engine port since that port is 1/8 BSPT. In my case, I needed an adapter to fit the sensor into the oil filter sandwich plate since the port on the plate was 1/8 NPT (i.e., I used a 1/8 PT or BSPT male to 1/8 NPT female adapter). Trust this helps!

It's probably NPT if the package says so.
From the Defi web site:

Are you sure your sensor is 1/8 NPT? I goggled the install instructions for the Defi BF Advance gaugesand it appears the sensor thread is 1/8 PT.

You are correct. I'm not sure how my brain added the N to PT. So just to summarize, PT=BSPT and not NPT?

Yes, evidently PT = BSPT. I goggled "What does JIS PT mean" and checked a few of the links and they indicated that PT was equivalent to BSPT.

Raising this thread as I finally had a chance to observe oil pressure for a moment and I'm not sure if I'm worried for no reason or not.

So, I only just checked cold/warm idle and 3k rpm pressures and they were:

Cold startup oil pressure: 7.5bar ~ 108psi
Warm idle oil pressure: 1.6bar ~ 23psi
Warm at 3k rpm: >4bar ~ 58psi

This is with the 25row oil cooler with the thermostatic plate (so it wasn't open at the time of reading), and the pressure sensor is Tee'd of the factory mounting point.

I have replaces galley gaskets last year. This should all be good, right?

Those all seem fine. Maybe a bit lower than typical but they’re in spec.

Nissan calls out >14psi at idle, >42psi at 2k rpm when warm.


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First and foremost, I would like to sincerely thank you for your youtube videos. The throttle relearn and how to check oil pressure ones have been very helpful. I went down the rabbit hole and was worried that my gallery gaskets might be bad but, after installing an oil pressure gauge, I believe that I'm good. I show 114 at cold start up and 27 after warming up at idle.( I still need to log what it's at at 2K, 3K, etc.) I installed a mini OLED gauge with the fitting in the sandwich plate. You have stated that this will give me a slightly higher reading than actual engine pressure due to it being pre-filter. Do you know approximately how much higher that this would read as my numbers look good but, I am interested in what would be considered low with my set up.

So far I love the OLED as it's less than 1-1/2" squared and easily attaches with Velcro pretty much anywhere!!

To me, the best oil pressure indicator, is with the oil temp at 180F and in first gear (7AT) foot brake on, AC off, with idle at 675-700 rpm.

Mine shows 21-23 psi, just after galley gaskets replaced on an engine with 58k miles.

Well, I may have been a bit premature. After driving the car for 20 mins, the idle pressure is ~14-15lbs. Looks like I will be tackling those gaskets next month when I'm off for a week.

Minimum hot oil pressure at idle is 14 psi

Thank you for your kind words on the videos, I'm glad they were helpful!

As for the oil pressure drop on the sandwich plate, my guess is 2-3 PSI, depending on oil temp and engine RPM.

This spring/summer I will datalog oil pressure before and after the oil filter.
I might even try a few different types of oil filters to see if the pressure drop is different with different filters.


As a single data point of reference, here are my oil pressures & temperature at idle on my 2011 G37, 6MT with 130,000 miles over about 1300 seconds (~21 minutes) with no oil cooler, not even the factory one.

http://www.the370z.com/attachment.ph...1&d=1732564815

If you want to boost your oil pressure a little bit. You can put a shim under the oil pressure relief spring. Start with a 0.010 thick shim. You have to drop the oil pan to do it. It's an old hot rodder trick.

On the VHR, the oil pressure relieve valve is used to limit the maximum engine oil pressure to about ~95 psi (depending on oil temp) This is used to reduce oil pressure on cold starts and at RPM greater than about 4,000.

When at operating temperature and below about 4,000 RPM, the bypass valve is closed, so shimming it up has no impact to oil pressure.
Shimming up the spring does increases the maximum oil pressure, which I don't think is a good idea.

Here is some data from my G37 6MT with 130,000 miles recorded in August:
• Up to about 4,000 RPM the engine oil pressure increases as engine RPM increases in a somewhat linear / straight line, due to the bypass valve staying closed.

• From about 5,000 to 7,500 RPM the engine oil pressure is held somewhat flat/level. This is due the valve being pushed open by the oil pressure and bleeding off oil pressure as the engine RPM rises.

http://www.the370z.com/attachment.ph...1&d=1732628547

About the data source:
I've developed a module that plugs into the OBD port, reads the CAN bus messages and saves it in human readable format to a CSV file on the SD card 20 times per second.

Engine oil pressure and diff oil temp, are not on the CAN bus. They are received via Bluetooth using an under hood mounted module that powers any standard oil pressure sensor, reads the analog output, converts it to a pressure value and sends it out to the OBD mounted module using Bluetooth. From there it is saved to the SD card.