Howdy, folks!

I’m curious how electronic MOP output is controlled. What is coming down the wires to its little brain to affect the oil delivery?
Is it a variable voltage? Is it constant voltage, but varied pulse width?
Anyone know?
Anyone know actual specifics?

Thanks!

 

According to section D of the FSM it looks like voltage directly from the ECU, there's 7 wires going to the MOP. 1.1V at idle at idle and it goes up with acceleration. It's a stepper motor inside with a position sensor.

 

https://www.rx7club.com/3rd-generati...sified-892750/

https://www.rx7club.com/3rd-generati...art-ii-895388/

https://www.rx7club.com/3rd-generati...-897507/page2/

https://www.rx7club.com/3rd-generati...e-ends-978918/

 

it works exactly the same as a drive by wire throttle, there is a stepper motor to move the plunger, and a position sensor so the ecu knows that what it commanded actually happened.

 

I don't have great data, but I measured the OMP position sensor voltage a long time ago. The position increased with RPM during a full-throttle pull at 10-11psi, which makes sense because the amount of oil should probably mirror the fuel flow.

 

^That’s my understanding too. Load AND rpm.

 

True statement. If you look at the FSM schematic wiring diagram, you'll see that the MOP stepper motor consists of 4 coil windings, arranged as 2 pairs of windings with a common terminal that goes to +12V when the car/ECU is powered up. So it's a unipolar 6 terminal stepper motor, 2 terminals (common to each coil pair) go to +12V and each of the remaining 4 terminals get pulled to ground on command via the ECU (i.e., 0 = ECU keeps an open circuit, that coil winding is NOT energized, and 1 = ECU connects to ground, coil circuit is completed & energized). In effect, the stepper motor plunger can be moved to any of 16 different positions from min to max plunger range (2^4 = 16 possible states).

 

The 2009+ Rx-8 OMP has a totally different and more modern design with plungers that are controlled by the ECU. Too bad that redesign came so late.

 

Thanks, guys! That is great info!