Oil pressure question

[Nevyn72]

A quick question for the brains trust out there.......

I recently installed an oil pressure gauge to my NB SE so can see exactly what's happening as I drive and was wondering if this is normal?

Once the engine is fully warmed up I see;
Idle: ~20-25psi
Motoring: ~60-65psi

However as I move off from a stand the pressure gradually builds to around 80-85psi mark before suddenly dropping back to the 60-65psi mark and staying there rock solid.

Is this normal?
Why does it happen?

[Regie]

Thats prolly the pressure relief valve buit into the oil pump that brings it down to normal pressure

[Nevyn72]

Thats prolly the pressure relief valve buit into the oil pump that brings it down to normal pressure

Thanks, I remember reading something about that but wanted confirmation that this was how it worked.

[Magpie]

Not sure the specs for the SE but for the NA the oil pressure relief valve kicks in around 50-64 PSI.

An alternative is to shim the oil relief valve and use something like a Peterson's remote relief valve http://www.petersonfluidsys.com/pump_acc.html to control the oil pressure. This is needed if you are operating the engine at high RPM all the time as the OEM MX5 oil pump has some issues when used at high RPM's often. Again this is probably only for engines that see 8,000 + RPM.

[Nevyn72]

Not sure the specs for the SE but for the NA the oil pressure relief valve kicks in around 50-64 PSI.

That sounds about right, just got back from a run through Nasho (I had to go somewhere to confirm! ) and the actual numbers are 58psi motoring and 20-25psi at idle.

Pretty sure a remote relief valve would be overkill in my situation......

[bootz]

So our normal oil gauge, provided by those nice Mazda people, not good enough for you?

[Magpie]

Happy to help!

I guessed a remote relief would be an overkill, but ...

[sailaholic]

So our normal oil gauge, provided by those nice Mazda people, not good enough for you?

You mean the one that is basically a warning light that looks like a gauge?

All nb oil pressure "gauges" are given their information by switch type sensor. Only Na ones were a "real" gauge. Even then the NA gauge has been shown to have some questionable accuracy deepening on the gauge / sensor and accurate you want it.

[Nevyn72]

So our normal oil gauge, provided by those nice Mazda people, not good enough for you?

You mean the one that is basically a warning light that looks like a gauge?

All nb oil pressure "gauges" are given their information by switch type sensor.

Exactly!

Ironically I actually used the circuit for the factory gauge to wire in a conventional warning light.

Having a (slightly, but more to come) modified Turbo incarnation of this engine, I like the idea of keeping an eye on what's happening with the oil pressure......

[JBT]

Only Na ones were a "real" gauge.

...and only pre 1995 cars.

[Lokiel]

So our normal oil gauge, provided by those nice Mazda people, not good enough for you?

You mean the one that is basically a warning light that looks like a gauge?

All nb oil pressure "gauges" are given their information by switch type sensor. Only Na ones were a "real" gauge. Even then the NA gauge has been shown to have some questionable accuracy deepening on the gauge / sensor and accurate you want it.

LOL - the most over-engineered "warning light" ever.

The water temperature gauge is the same too unless you do the "linearisation mod". Normally it sits at the 1/3 mark but will move straight to the 2/3 mark when you're already overheating badly.

[ED_MX5]

How do you do the mod to the water temp to make it read right?
I have noticed it read weird. But as only new car to me, I have not looked further.

[Nevyn72]

How do you do the mod to the water temp to make it read right?
I have noticed it read weird. But as only new car to me, I have not looked further.

Detailed instructions here.

http://www.mazda-speed.com/forum2/index ... 534.0.html

[speed]

How do you do the mod to the water temp to make it read right?
I have noticed it read weird. But as only new car to me, I have not looked further.

Detailed instructions here.

http://www.mazda-speed.com/forum2/index ... 534.0.html

Another worth while mod for me. Thanks



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[ED_MX5]

Cheers Nevyn, having read that post, I think I may just have a separate gauge. I am planning to have oil pressure and temp, so one more above radio wont hurt. Will nicely fill the hole I think