Maybe a dumb question but, what is the benefit? Better oil lubrication between the bearing and e shaft? I'm in the middle of a rebuild and my bearings are showing copper pretty bad.

Atkins link to product

 

Thats my understanding. More pressure may be needed with it as well maybe.

 

i think it ends up having more oil in and around the journal. you should price out the competition number and the FD/rx8 number, as they are the same design.

they actually are different, the FD part is graded by size, and so it allows a more precise fit

 

Mazda switched to a three window bearing on the FD's 13b and also on the Renesis engine.

It seems to me that it allows the oil to lubricate the bearing from three places instead of one and then the eccentric shaft rotates to distribute oil on the rear bearing.

I thought the shaft got it's lubrication from the front of the engine that it distributes to the rotors so if there's a three window bearing there, it allows oil to flow into the shaft every 120 degrees as well as allowing the journal to get more oil as well.

I wonder if it's like some main bearings on a boinger that have a slot in the middle of them and one oil hole since according to REC's writeup that I link to below, there's a slot milled into the stationary gears as well.

These guys have a good writeup:
http://www.rotaryengine.com/services/bearing3window.htm

On the 13B build I'm working on, I'm going for the three window bearings as well as the hardened gears. While I want power, I really want reliability with it so I don't grenade my new rotor housings or anything else I bought and have machined. Of course I take care of it like you're supposed to, always letting it warm fully if I start it, check the oil every two weeks, change the oil every 3000 miles and I keep my eyes on the gauges and I also put in a 160 thermostat but I think the rad needs coring again.

I'm definitely going to do this and I already have the OMP rebuild kit but I'll need another gasket. Excellent writeup:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/richard-sohn-metering-pump-adapter-install-809207/