omp per engines. why 2injectors v. 4 injectors
 

The 12a had a mechanical OMP with 2 lines feeding the carb, right where the fuel was atomized. which apparently did a fine job in lubricating apex seals.

The return of the 13b saw 4 injectors for oil. two on the rotor housings, two in the intake manifold. of course changing from mechanical to electronically controlled in the series v cars.

the whole thing gets jacked up by the 13b-REW (perhaps the RE also). Which goes to two oil injectors in the housings.

How did Mazda get away with two less injectors in the 13b-rew? Considering the MSP if I recall, had six injectors by the time it ran it's course.

early MSP had 4 injectors, then went to 6.

there is no magical right or wrong, in fact im of the concept that oil injectors can hurt the engine, as injecting dirty engine oil generally causes excessive wear where the oil is injected into the engine on the housing and seal.

the whole thing is really about lubricating the seals, AND using less oil.

so if the 12A worked ok, the GSL-SE/S4 setup is actually better, and uses less oil (actually the turbo is capable of using quite a bit more)

the FD again, uses less oil, and i'd say condition of rotor housings at a given mileage is about the same as a 12A, while making 2.5x the power.

the Rx8 is different, as the engine needs lubrication in a different place, and then they found that it also still needed oil in the center of the apex seal =6 injectors

so the oil is too dirty for the combustion chamber, but is still ok for the bearings?

what brings this on is I have a gsl-se motor (no intake manifold), and a 84 12a. my intention is to make a 4 port 13b with a DCOE style EFI. using the center housing injectors as a primary and the injectors on the throtlebody as secondary. it would be simpler for me to use the 12a front cover and OMP to feed the injectors on the 13b housings. or I could use the 13b front cover and try to figure where to tap the two other injectors. There is a 40% chance of running boost in the future. although at lower levels due to the 9.4 CR.

crankcase oil isn't meant to be burned, being that it is laden with wear material and carbon i'm sure that hinders it even further from doing a good job in the dry and extremely hot internal combustion environment where it really shouldn't be. 2 stroke oil has a higher flash point, much more suitable for internal combustion lubrication. OMP engines always disassembled with dry rotors and seals, in some cases the apex seals even being stuck because of dried carbon. engines running premix always had a film of oil on the moving parts, rotor faces and even less carbon deposits.

if you are curious, find some worn rotor housings and grab a straight edge and light, you can see physical wear patterns start at the metering nozzles on just about every series of engines that used them. engines that didn't place injectors in the housings generally only show wear at the extremity of the housing since that is where friction and heat is the highest from the apex seal(since it has 2 faces adjoining that cause the metal to expand and contract as well as gather and disperse heat), as well as wear.

OP, as far as i recall the oil metering pumps from the SA, FB and S4 FC are all interchangable, meaning they will all fit on each other's front covers. so you can use an FB front cover and use an S4 4 port OMP.

so i ran across the FC specs for the OMP, and i think it can deliver MORE oil than the 12A... so more research is needed.

i think if the FD only ran rotor housing OMP nozzles, then that should be ok still. i think i would try to use the FC pump, just because they work, and maybe just run 2 lines to each injector or something. possible that you can just plug 2 of the holes in the FC pump too.

The 12A OMP can not provide oil to the injectors on the rotorhousings as it will blow the internal o-rings and cause a massive leak onto your front cover or will push the hoses off of the barbs. If you notice, the GSL-SE used banjo bolts and a more robust OMP.

so i'm putting an FC together, and i did the metering system yesterday. the metering nozzles are actually different. the nozzles that go into the engine have a big orifice, 2mm? and the nozzles that go into the intake have really teeny small ones, maybe 0.5mm?