Here is the deal. I attempted to install a Rotary Aviation OMP adaptor on my 93, but unfortunately it will not fit with my A-Spec 500r SP long runner. It leaves only about an eighth of an inch clearance between the end of the OMP pump and the front rotor exhaust header. Too hot! I have the turbo and exhaust header off right now to have some bungs welded and was going to remove the OMP altogether and just go premix. However, the car is a daily driver and I would really like to use the OMP but with a two stroke oil reservoir.

So, I started looking at how RA engineered their adaptor. It appears it is nothing more than an input for an alternate source of oil that extends the drive shaft from the engine gear to the OMP pump. I also found it interesting that the adaptor actually reduces the size of the internal oil reservoir in the OMP by half. If you look at the front plate on the engine where the OMP connects to the motor you notice it is designed to allow for a cavity that marries up to another cavity in the OMP. This creates an internal reservoir for oil to feed the OMP. When the RA adaptor is installed it creates a block off that cuts off half of the capacity of the internal reservoir. It also blocks off the source of pressurized oil into the OMP and relies on gravity to keep the smaller reservoir supplied.

All of that got me thinking; I have not heard any comments about the RA adaptor not working for those who have the space for it. Why couldn’t you simply tap an input source directly into the internal OMP oil reservoir? It would be necessary to block the pressurized motor oil from entering the OMP from the engine, but that seems doable. I did some measuring on the case of the OMP pump housing and it looks to provide plenty of space for an appropriately sized input nipple. There is a small hole that provides engine oil to the OMP reservoir that would be easy to seal up.

So here is what I would appreciate input on. This all seems too simple. There are a lot of really experienced people on this forum, so if this would really work, why hasn’t someone already done it, or have they?

I hope some of you engineer savvy people will trouble shoot my idea. I would really appreciate you comments good or bad. Thanks

 

I think what you said is exactly right. The adaptor is just a way to keep your stock parts clean and the mod reversible. I read about someone blocking the pressure hole off a few years ago...with JB weld. There must be a better way to do it.

 

Thanks, anyone else care to chime in. I am most interested in feedback on tapping into the housing on the OMP. If it would work I could have exactly what I am shooting for.

 

Might want to contact the manufacturer and discuss with them.

 

Someone already did this with a thin plate that goes between the omp and the bolck. then they tapped the OMP and fed it from a separate reservoir. Its tedious, but it would be worth retaining the OMP in my opinion. Allows you to run synthetic in the engine and 2 stroke in the OMP.

Best of both worlds.

 

the only drawback i can think of in designing your own "plate" as mentioned above would be that you'd have to find a way to extend the omp driver. since the pump is mechanically driven and splines into the front cover. as for tapping the omp. i'm usure of it. i'll look at the rx8 pumps tomorrow at work and see what i can figure out for you. i think they're similar. i could be wrong

 

This is what i did a while back when i had My FC.I forget the thickness of the plate but it would have worked fine.I am sure the FD omp can be tapped as well.

 

Thanks for all the input, and especially the pictures. As for the plate, I am not planning on using a plate. I am proposing to tap directly into the small internal reservoir in the OMP. I have been looking at the concept using an old front cover which still has the OMP gear installed. It all looks very doable. I am not sure how much the OMP relys on oil pressure from the crankcase to push oil to the rotors. In looking at the OMP it appears that the only function oil pressure would accommadate is making sure the small internal reservoir doesn't starve for oil. RA seems to rely on gravity to accomplish this, I am thinking about installing a small pump in-line with the feed hose. A pump much like those used to supply water in an RV should work. They activate with a lose of pressure and shut off under pressure. It may be over-kill but I am a little concerned about oil starvation. Thanks again, any other thoughts are welcomed. RD

 

You have to use a plate of some sort to block off the other oil passages. You could tap into the OMP all you want, but you would end up just mixing the 4 stroke and 2 stroke oil in the end.

Tapping the reservoir will just be your route for feeding the OMP from your new 2 stroke source.

 

for reference check this thread:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/mod-omp-2-cycle-oil-injection-585049/

 

Thanks, this thread helps a lot!!