Thinking it through some ... I don't think the difference in output will be significant, but it will always be less than stock . As stock you have a significant positive pressure on the inlet so any leakage will flow towards the engine vs the Sohn where there is next to nil pressure and any leakage will flow back towards the inlet.

Started a new thread on this :

https://www.rx8club.com/series-i-tec...cation-268559/

I believe the oil input location to the OMP on the front cover is not pressurized at all. It looks like an oil return, and a gravity one at that, and has a what looks to me like windage passage slow the flow down to eliminate air from the oil flow. I could be wrong, however, I didn't spend a lot of time understanding the front cover oil routes. Also, I had no problem with my Sohn self priming the pump after multiple disconnections of the feed line, and disassembly of the pump itself while on the car, and using a gravity feed only on another pump on a test stand with multiple times disassembly/reassembly.

Feel free to chime in if I am incorrect in any case. It would be nice to have an accurate record on the forum of how this thing works after only 15 years since the first one rolled off the assembly line.

Just checked this out .
Pressurised oil goes through hole at bottom left then comes into the chamber via that nozzle (approx. 1mm dia.) .There is also a hole that would relieve the pressure of oil heading to the nozzle. It would then fill up the chamber which looks like it's designed to take the air out of the oil as you mentioned. Oil then flows to the hole in the bottom of the chamber and off to the omp inlet. There is also a small hole approx. same size as the inlet, at the top of the chamber cover (not shown) which is probably there to to let the air out of the chamber .So .......... it looks like you are correct . The oil flows to the omp at a very low pressure .
Good to know that the pump does self prime . Looks like I was wrong on both counts ....

https://cimg4.ibsrv.net/gimg/www.rx8...b168036a69.jpg

Hopefully this thread isn't dead. Just picked up two 8s (for 900, a steal) and found that my '05 is smoking like a freight train. Disassembled OMP, tested POT, found that it's faulty. Supposedly the POT (potentiometer, i.e. the position sensor) is the same as a throttle position sensor on some other Mazdas, but I can't seem to find the right one. A little assistance? Go easy on me. I may have missed it in the 14 pages of this thread.

This thread is fantastic. I have been reading these pages for 12 months. Got myself an 05 project car after a bit of a break from rotors. The 8 has been going well other than a couple of codes to chase down. Mostly resolved or or just learned to deal with such as the pesky p0139.

Had a couple of p1688 codes that until now i have been able to clear ok. Now i have a rock solid code so i will attempt to clear by adjusting the mop. I suspect that the mop has forgotten its zero point to end up at this point. I will report back with results when i can.

Thanks to OP and all other posters for this thead that took a long time to chew through! Amazing.

Just a follow up. Had a mini win after adjusting MOP switch. After one failed attempt to set switch that instantly set off CEL. Happy spot was full travel towards firewall then forwards a whisker.

Reconnected neg terminal then winner winner. No more CEL. Did full heat Cycle while still on stands. Shut down then reset again via batt terminal to ensure it was not a fluke. All good so far and done about 6 full heat cycles and still no CEL. But still on stands so time will tell.

Will report back if any problems after decent load testing on road. Hope this helps someone else!

Nobody has ever found a replacement sensor switch that I’m aware of. If it goes bad the only known solution is to buy another MOP, either used or new. Seems kind of dumb, but perhaps Mazda considered the assembly too critical to be swapping sensors. Plenty of people have done it, but we don’t really know the true outcome.

Dragon,

Chances are you fixed it. But the OMP switch can also be bad. Some say its a potentiometer, but it isn't, its a switch.

I have mine adjusted on a knife edge apparently. When it is very hot here (over 110 approx) and I shut the engine down and then restart within 5-10 min, the sensor (switch) and the OMP assembly heat soaks enough that when I start again it goes into limp mode. If I shut down again, after running for about 30-45 seconds, the system cools down enough from the fans running, I am assuming, to restart and not go into limp mode. When its cooler outside, or if I let the car sit for longer than 15 min or so, I never have this trouble. Its a pretty fine adjustment apparently. I need to go under there again and fiddle with it a bit so this doesn't happen anymore, I doubt its a bad switch, its probably from my guesstimate initial adjustment.

Someone else on here is getting limp mode when warm and it might be the same thing. Kind of a guess, but I was thinking the same as you; switch might be right on the edge of adjustment. It could just be bad internally. Only one way to find out; try adjusting it.