A Question Of Ohm's

[Weaselman]

Would anyone know the ohm range of stock RB series oil pressure senders?

I.E. what would the ohms be for upper pressure indication on the guage and lower.

I have an RB20 DET and need to know the range to program a micro controller to do some fancy things.

Any help is much appriciated.

[KiwiRS4T]

I suspect you will have to replace the stock sensor with something a bit more sophisticated such as this:

http://www.nzefi.com/product/oil-pressure-sensor-0-150-psi/

which tells you that 0.5v = 0psi and 4.5v = 130psi

[Weaselman]

Something to look at but If I can find out how the stock ones work I can write it into the code without the need for a spressure switch that costs more than what I need to spend for the micro controller and switching relays.

[iruvyouskyrine]

This is for R34. No idea what R32 is but this should get you in the ball park. Either way I recommend not using the standard nissan sensor.

[Weaselman]

Cheers mate thats a big help.

Do you know if RB's use a seperate switch for low oil? And if so where does it hide. Or does it rob a signal off the sender for the guage?

[Dan_J]

on the stock 2pin r32 oil pressure sensor one pin is for pressure reading and the other pin is for the red light indicating too low or no oil pressure

[Weaselman]

Thankyou kindly.

I was hoping to work around the system but seeing as it shares the same sender I'll have to re think it slightly.

[XR Pilot]

If memory serves the dash cluster uses pull ups connected to a 10V supply (as if they used battery voltage the gauge readings would fluctuate with charging voltage). To make this work you need to build a voltage divider to your MCU with the oil pressure sender wire tapped in and forming the voltage supply to your divider. Check the workshop manual for resistance at low and high pressure (or better yet, use an air compressor and regulator on the factory sender and check with a multimeter; they are 20 years old after all). Connect your voltage divider up to the sender, key on and bridge the sender with resistors based on the workshop specs. Measure output of the divider, swap resistor, remeasure. That's your calibration voltages for low and high pressure then map those voltages against the pressure tested and you've now got your sender calibrated. If that doesn't make sense let me know if you want a diagram.

[Weaselman]

I'll never say no to a diagram but I know what you are driving at.

[breaker1845]

I'm interested to know what you are intending to use the micro controller for exactly. I.e. the functions you are going to program to display or produce what you want. I think everyone else has covered the rest as you can test the actual pressure sender to find out the ohm range.

[Weaselman]

The micro controller is going to read the voltage off the oil pressure sender and when if it drops below a certain level when the engine is running flat out it will trip a relay that will kill the power to the coils and protect the engine. I'm racing in a flying mile event later in the year so this is just some built in insurance as my ECU doesnt support parameters to do this without expensive modification.

I've whipped this system up for about $50 and installed it in the car with an override switch for cold starting and a set of warning lights to get my attention. I wanted to have the spark cut if the pressure drops at high RPM and boost to allow me to stop the car with enough oil in the system to protect the internals. So before the factory light comes on or the gauge drops past where I want it too.

Its a shits an giggles project that I can install in any car I want like my cruiser or my wifes 260RS Autech for minimal money and without any serious modification to wiring.

[breaker1845]

Sounds like a good and inexpensive idea. Would be good to see the results of the setup when you are done.

[KiwiRS4T]

The micro controller is going to read the voltage off the oil pressure sender and when if it drops below a certain level when the engine is running flat out it will trip a relay that will kill the power to the coils and protect the engine. I'm racing in a flying mile event later in the year so this is just some built in insurance as my ECU doesnt support parameters to do this without expensive modification.

I've whipped this system up for about $50 and installed it in the car with an override switch for cold starting and a set of warning lights to get my attention. I wanted to have the spark cut if the pressure drops at high RPM and boost to allow me to stop the car with enough oil in the system to protect the internals. So before the factory light comes on or the gauge drops past where I want it too.

Its a shits an giggles project that I can install in any car I want like my cruiser or my wifes 260RS Autech for minimal money and without any serious modification to wiring.

The reason I suggested you would need to change the sensor is that I suspect that the stock sensor will not react quickly enough to save your engine. If you do intend to stick with the stock sensor I suggest you at least get a brand new one.

[Weaselman]

Already done mate. I'd never trust an old part in a new system. Also I'm setting the cut out fairly high so even accounting for delay It should have enough pressure in the system to minimize damage.

I.e. If you set the relay to trip when the needle drops below a quarter on the gauge you should still be cutting the spark before its down to a critical level.

[Ben C34]

Good luck with it, but I imagine having problems with hot idle, unless revs are factored in.

[jiffo]

Couple of the lads on the GTRUK forum have been toying with the stock sender and have proved it's not worth a pinch.

This is NOT the way to go if you want to save an engine.

These things will still indicate gauge pressure even when pumping air.

[scotty nm35]

Might have trouble starting the engine unless there is an ignition on delay.

Relying on anything electronic is a little silly imo, and cutting ignition could easily cause an accident. I hope you're not in front of me when it happens...