The plot thickens...


So, I was at the dealership on Friday. They recently changed out my tire pressure sensors and one of my tires had something rolling around inside it, so I had them remove it. And I decided to ask them about the oil pressure. Their tech told me first of all, that's not where you're supposed to measure the oil pressure because it's an "aux port" and not the main bearings. (This is the plug on the block next to the a/c compressor.) He said the idle pressure is probably "40 pounds or so" at idle, at the pressure switch, and he's not surprised at all I'm only reading 4 pounds at the oil gallery. He said the main oil gallery plugs are on the bottom of the engine, on the heads, but he didn't have time to point them out to me right now. Also said that if there was low oil pressure, the pressure light would come on because the pressure switch activates at around 15 psi. (They also told me my Bluetooth scantool adapter messed up their TPMS module and that's why it didn't work, but that's another subject.)


I've read on here that the stock oil pressure switch goes on around 2 psi, not 15, so I built a pressure tester to see who's right. It's a section of PVC with an air chuck on one end and I put 1/8" threads in the other. Screwed in the stock pressure switch, charged up the pressure and measured ohms between the body of the pressure switch and the wiring terminal. As expected, it shows open circuit when there's pressure, and it closes when the pressure goes down, turning the dash light on. So I started at around 8psi and lowered it slowly until the contacts closed. Turns out around 2.5 psi is where the switch closes.
http://www.ls1m.com/demo/p1.jpg


It did that several times, repeatedly, always closing at 2 or 2 1/2 psi. So that's the first thing. Don't trust - measure. Tech at the dealership was full of it, so I'm going to assume that the other information he gave me is bogus. Like, telling me to never disconnect the oil pressure switch or it'll "mess up" the ECU. Hmph. I think not.

So I did a little more experimenting. I put the stock sensor back & put my gauge sending unit in its place. I turned on the car & pressurized the cylinder until I got about 5 psi on the gauge, around where it goes once the oil is warm.
http://www.ls1m.com/demo/p3.jpg


And on the cylinder:
http://www.ls1m.com/demo/p4.jpg


So when my gauge is reading around 5 psi, I'm actually at 11. Interesting. Then just for giggles I put 35 psi on the cylinder and compared it to the gauge:
http://www.ls1m.com/demo/p5.jpg


http://www.ls1m.com/demo/p6.jpg


So it looks like I have a problem with the gauge. But, at least I'm not actually running 4-5 psi at idle. Oh, and the oil temperature is right around 205-210degF at hot idle, according to the obd2 scanner.


I'm going to contact prosport gauges, but has anyone else seen something like this?

Bad when a service guy guesses and doesn't look at the service manual. It's all there. Dummies!

Well ProSport Gauges says the gauge was 4 psi off, so they sent me a new gauge & sending unit and it's also way off. Just tested the new pieces: I put 10 psi in my tester and the gauge shows around 4. Put 30 on the tester (verified with two tire gauges) and the gauge showed around 22-24. ugh... I'm returning it to get my money back.

Can someone recommend an ACCURATE oil pressure gauge?

No experience with them, but I'd like to get the SPA Technique Pressure/Temp dual gauge...

.1psi resolution with high quality sensors that read to around 250psi...also programmable and temperature recall with multiple alarms - hence the price of these units.

I'm specifically looking at this one:

https://www.spatechnique.com/product...ils.cfm?id=378

Holy cow that's expensive. Nice gauge though...

Well, I finally got a better gauge. It's an autometer 5953. It was only a pound or so low when I tested it. Here's 5 psi:
http://www.ls1m.com/demo/gauge5.jpg
and 10 psi:

http://www.ls1m.com/demo/gauge10.jpg

and 40 psi:
http://www.ls1m.com/demo/gauge40.jpg


It looks real close to stock. The letters are white so you can read it in the day time:
http://www.ls1m.com/demo/gaugeday.jpg
and at night it lights up red:
http://www.ls1m.com/demo/gaugenight.jpg


I used a piggyback fuse adapter for the +12v (fuse block under the dash) and I used the purple wire for the dash lights (mentioned here: http://theattack.rallysportdirect.com/2013/05/how-to-install-ati-60mm-vent-pod-wdefi-gauge-on-2013-scion-fr-ssubaru-brz/


With Amsoil 0w20 signature series at 210F I'm reading about 8-10psi at the port on top of the engine. So it's not 4psi at idle after all...