At first sight, Mazda using a [US] Imperial thread may seem strange, but these threads dominate gauge fittings so it makes sense for Mazda to conform rather than require a metric to Imperial adapter in workshops.

 

Well the stock sensor is BSPT (British Standard Pipe Thread), so it's not US. It's very close to NPT, to the point where some will screw it in there anyway, but not quite the same (28 threads per inch vs. 27), so one set of threads will get messed up. Aftermarket sensors are almost universally NPT, at least in North America.

 

ok, so 2 banjo bolts, one on the inlet to the 2nd oil cooler for pressure, and one on the outlet of the 2nd oil cooler for temp (keep them on the same side so routing is cleaner)?

That gives me oil pressure and engine oil temp before the engine to make sure it's in range and i'm not putting overheated oil back in the engine...?

 

Well I finally set up a Depo 3 in 1 oil p , oil t , water temp and volt meter
I could not see how the **** i could possibly get the front cover banjo bolt out so i put my 2 modded banjos in the lhs side oil cooler . Its only a 10Bar oil p meter and peaks out on the s2 motor It was orignally bought for a 80's Lambo restoration, but at least i can see if oil p is stable
Its good to see how things are running a geez oil yemp takes a fair while to come up

 

Oil pressure seems to be consistently over 150psi ( 10.2 Bar at full throttle,

 

What is your pressure at 3000 rpm, engine fully warm?

 

At idle fully warm its about 2.7- 3bar, ill check but at 3krpm i think it may be as high as 6bar

 

Correction when oil warm at 83c 2.7-3 bar at idle and 8 bar at 3krpm

 

For my s2, oil press at idle is between 20-50 psi, weather dependent at ~operating temp. Cruising was around 60-110 psi IIRC and WOT is always over 150 psi. That is normal.

I find it depends much more on load than it does rpm.

 

The Mazda reference R3 oil pressure is 5.0 bar (500 kPa, 5.10 Kgf/m2, 72.5 psi) at 100 deg C (212 deg F) at the pressure take-off on the engine casing. The pressure at the oil coolers should be slightly higher to account for pressure losses in the in the oil lines and oil filter.

The oil pump is a mechanical gear-rotor (rotor-type) pump driven by a belt and pulley. It's speed and hence oil flow without back-pressure is proportional to engine speed. Pumping into high pressures reduces the flow and the pressure relief valve limits maximum pressure (115 psi for S2 compared to 80 psi for S1), but in broad terms pressure is roughly proportional to engine speed.

The achieved oil pressure for a particular engine depends on a variety of factors, notably oil temperature and oil grade but also including how dirty the oil is. I expect a well-used engine to drop a little pressure on WOT compared to no-load values, say up to 0.2-0.6 bar over 3,000-9,000 rpm. Idle oil pressure varies considerably with circumstances and I'd expect anywhere from 20 to 40 psi.

Oil pressure won't necessarily warn you of a failure. I lost half a track day when an RX8 cracked a housing at one of the oil ways and deposited oil over 3/4 of the track length; the driver, an experienced track and race driver that I trust, said that he had no indications of failure and I could see how he would still have had oil pressure for some time.