Observed Oil Pressure with a gauge

MotorvateDIY

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.

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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).

dts3

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

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No.

dts3

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.

Rusty

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.

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dts3

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

dts3

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

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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).

dts3

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.

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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!

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?

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!!

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.

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