Observed Oil Pressure with a gauge

40 to 332

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!

SouthArk370Z

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

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40 to 332

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.

dts3

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

40 to 332

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.

filip00

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?

Averying

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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Da Flash

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!!

SG4247

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.

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Da Flash

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.

redondoaveb

Minimum hot oil pressure at idle is 14 psi

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MotorvateDIY

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.

Attached Images

370-1_sm.jpg (300.8 KB, 56 views)

Rusty

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.

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MotorvateDIY

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.



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.

Attached Images

EOP_bypass.jpg (209.7 KB, 42 views)