Any of you guys that remove the OMP and run premix, did you remove the OMP drive gear and shaft? It appears most people leave the OMP shaft installed--prehaps cause they don't want to go through the trouble of taking off the front cover. I'd like to know if anyone has miles on their engine without this shaft installed--and of course running premix?

I'm doing the TII conversion into an SE. Planning on running straight premix and thought why can't I use the OMP mount connection for my turbo oil drain? It's in roughly the right spot and seems like it would work OK.

I see only one problem and it may not be that bad. There is an oil journal that runs from an inlet in the opposite side of the front cover, through the front cover, and then feeds the OMP shaft and pump with oil. I presume the excess oil just drains out the gear end of the shaft and a little hole that is drilled on the OMP mount. If I remove this shaft the oil will have no restriction and would result in less backpressure on the oil feed system--since the oil can then just drain back into the pan via the front cover. From what I can tell the OMP is the last component in the lube system before draining back to the pan. Would the oil system just adjust and feed more oil to get the same system pressure drop? Definitely don't want to screw up the the oil system/engine.

Thanks in advance for your help.

Scott

 

I am also doing a TII conversion.

I removed my OMP and the shaft and got a cover from k2rd.com

I would also like to know about this. I doubt its a problem though

 

The OMP is fed with oil from a possitive pressure source..... not good for an oil return.

BTW, there is a small boss just below where the OMP it attached to the front cover. Just looking at it makes you wonder why they put it there.... its perfect for an oil return. I've never seen a 12AT, but its my guess that the oil return line is setup to go through that boss.

 

Thats what used for my oil return.

what about the OPM shaft, does it need to be plugged or something.

 

I'm going to use a block-off plate, and hope that should be enough. The shaft itself has an oil bearing somewhat similar to the turbo (only not as good, cause it won't see the rpms and heat that turbos do). It shouldn't see much pressure, so hopefully the block-off plate will be enough.

 

No doubt, the small boss in the front cover would be a good turbo oil return. The OMP location will work just as good. I'd just rather use a hole that already exists and would have to be blocked off anyways.

fatboy7, yes the OMP is fed by +pressure oil but it's only like 3/16" diameter while the turbo line is 1/2-5/8" diameter--both should drain ok--consider that the turbo line is also a +pressure feed. The problem I see is will the loss of the OMP shaft "bearing surface" impact the rest of the lube oil system. A loss of oil backpressure on the oil system will cause an increase in oil flow since the oil system pressure drop is now lower--but I think one or both of the oil control valves will compensate.

I'm looking for verification by someone that is currently running without the OMP shaft.

Scott

 

Shouldn't the return line for the turbo be exactly 90 degrees since it's gravity fed? Will it still be like this if you use the OMP location?

 

Anyone else?

 

Bump again!

 

The small indentation in the 84/85 cars is where the turbo drain is on the 12AT cars. It's the same place as all other Mazda Turbo Rotaries.

USE it. Keep the mechanical OMP, leave it on the max setting, and don't worry about pre-mixing.

 

Also the higher the drain, the more likely you'll drown the turbo bearings.... the lower the better. Honestly, if it weren't for all the horror stories I've heard about putting a fitting in the oil pan, I would have done that. It drains better that way (or allows you to mount the turbo lower, if thats an option).

 

Isn't that good to keep the turbo bearings drowned in oil?

I thought that's how all bearing surfaces worked--they need to be totally filled with flowing oil. Now not allowing the oil to flow is another problem--but I don't think that would happen in this case.

Thanks for your input.

Scott