Sohn OMP adapter

The Sohn adapter is basically a metal slab with a few holes in it, and a nozzle that can connect to a hose.



The point of this adapter, is to stop using engine oil to lubricate the apex seals in your rotary engine. This is a good thing because:

1. Your engine will no longer burn oil from the engine
2. Your seals can be given fresh oil that isn't dirty
3. You can feed your seals 2 stroke oil, which is meant to be burned.
4. If you're a firm believer that you can't use synthetic oil because it's bad for the seals, using synthetic oil will no longer an issue because your motor oil isn't being used for seal lubrication!


First off, you're going to need the adapter, it costs about $100, and you'll have to get it directly from Richard's website (or email him): http://www.rotaryaviation.com/oil_injector_pump_adaptors.htm

It took about 3 days for me to get the adapter.. I also bought a bit of clear hose, a matching nozzle, and some sealant paste.



Now, before you do anything, you're going to need to remove your car battery. Even if you haven't done it before, it's a cake walk. Just remove the neg batt terminal, the pos terminal, take out the batt, and take out the batt base. Once it's out of the way, you'll see the OMP, located just to the left of the engine. You'll also see some clear tubes:



You'll need to unhook the black coolant hose next to the OMP tubes, so that you can move the OMP tubes to the left of the hose. Because of this, you will need to make sure your car is cooled down and the coolant is room temp. I unhooked the coolant hose and the coolant kept pouring, so be quick with this step. When you're done, it'll look like this:



Now we're at the hard part. This step can take you just a few minutes to several hours. In my case, I had to remove my front bumper, so I could remove my turbo intake pipes and the pipes leading from the turbo so I could get access to the OMP from underneath the car. I also had to remove the bottom engine tray.

The OMP is attached by 3 bolts. One is reachable from on top, the other two I had to crawl under the car to unbolt. The lower bolt I could see, the second one I had to feel for.

At any rate all you need to do is unbolt the OMP, then reinstall the OMP - but with the Sohn Adapter in between the engine and the OMP. The Adapter will block the engine oil from reaching the OMP. There is a rubber gasket that seals the OMP oil input... if that gasket falls out, make sure you reinstall it! Without it your car will leak oil.


Once the adapter is installed, you're going to need a source to hold the oil and feed it to the adapter. The easiest solution is to drill a hole in the bottom of your windshield washer fluid bottle and fill it up with 2 stroke oil.



The washer fluid bottle is a great choice since it is designed to hold liquid, not slosh around, and has a tiny pin hole in the cap to allow the container to not create a vacuum as the liquid is used up. I am strongly considering buying the 2006+ washer bottles since they're transparent. They run about $60 from mazda dealers.

I used a standard vacuum tube with a screw in it to plug up the normal exit of the washer bottle.

Just route the hose to the adapter after filling the bottle with 2 stroke oil, and connect it to the adapter.

The final product will look like this:



I like royal purple for synthetic oil.

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User Comments


i'm new to this engine so correct me im wrong, but dosent this engine as no cam shafts to oil feed or major bearing to lube (c'z rotors counter-weight each other) so to me it seems that the engine is accentually doing this but in a big scale. (not for turbo-ed-oil-needing-turbos-engines)
does anyone have input on how well this works and wether or not you need the adjuster? I want to do this mod and have an oil leak on the OMP so now would be a good time to do this... Thanks for any input...
RX-8 burns more gas than oil. I wouldn't worry about burning oil, really. Adding in a larger oil pan would be a better idea than running out of secondary oil that feeds to the seals w/o any adjustment of how much is going in. RX-8 ECU controls how much oil is fed and that's very delicate process. Earlier RX-8 engines failed because the ECU wasn't giving out perfect oil feed.
Installed the OMP, and its great! I replaced the washer fluid tank with 2 smaller ones I purchased at Princess Auto. Had to custom make a braket that could hold both tank, then to screw it in at the same holes where the washer tank originally was. I then put the sensor for the washer tank in the premix tank so I could get a warning that it is almost empty. We did 2 RX-8 the same day, took about 10 hours (5 for first one and 3 for second one). Pretty much we winged it. Looking at this guide, its exactly what we did. The bolts are a bitch though (pardon my language).
Terry, where did you get those tanks? i cant seem to find them at that website. how did the bracket look? what did you make it out of? do you have any pics. i want to do this mod, but loosing my washer tank is not a good plan for me since the salt from all of the snow gets on my windows. thanks
Whether an RX-8 burns more oil than gas is irrelevant. The point is we're using the same oil being fed to the engine for lubrication for consumption and lubrication of the apex seals on the rotors. This is what causes a lot of problems also, and it's known that if you want to use synthetic in the past they ate up apex seals so you couldn't. On top of that normal motor oil is not designed to be burned like 2-cycle oil. That's the benefit of having this adapter on the RX-8; clean and proper suited oil for the application and allowing you to use synthetic to lubricate the rest of the engine.
Brian - I got the tank at Princess Auto. They are made by Power Fist. It is a windshield washer tank kit, with all the accessories (switch, wires, etc). You only need the tank. The bracket was pretty much a bit smaller than the size of a license plate. We made it of aluminum, so it is really light. Make sure to drill the holes at the correct place on the bracket, so you can attach 2 tanks (one for the premix and one for the windshield washer fluid). There is a picture here: http://forum.ottawamazda.ca/showthread.php?t=6045
Mazda - Ireland recommend oil @ 5W30 GRADE Semi Synthetic - is this not a good idea ? Comments please.........
What type of sealant did you use on the gasket?
what a cool idea ive been premixing for a couple of years now is the adapter compatible with older rotaries or is there one to suit ?
I don't own a RX8 but I've owned FB-FDs and know the concept. For those that still don't understand how this works, it's basically an adapter that blocks the original engine oil source to the OMP. Not only is it a blocking plate from engine oil, it's also a sandwich adapter that has a barb fitting to receive oil from an alternate source(reservoir of 2 cycle oil) that goes thru the adapter to the OMP still. Unlike what Soravia thinks the ECU still controls the OMP and the amount disperse. Again all the Sohn adapter does is gives it alternate source of oil of your choosing while blocking engine oil, so you can run synthetic in the engine without worrying about messing up seals.
I live in new zealand and we have been doing this on our rotaries here for 20 years or more. It really works .My car got 120,000 miles before needing a rebuild.I run bel ray 2 stroke oil .It works really well
I just removed my OMP. i just wanted to give everyone who is going to do this some advice. the bottom bolt, and the upper bolt that is hard to get to, are easily accessible through the passenger side wheel well. just some advice to help you guys
why not just premix 2 stroke oil in the tank
Is the oilfeed thats passing the driveshaft from engine totally blocked ? or is there an passage via gasket or a groove in the adapter to lead the oil back to the engine? Not to build up oilpressure to the gasket which can cause oilleakage
i believe that the adapter just blocks the oil from the engine. but the pump pulls from the 2 stroke, leaving there no possibility of any pressure being built up.
How about the new Series 2 engines? Are these any better, or is a Sohn a must for these as well? The OMP is supposed to be electronically metered, more accurate?
I just installed this adapter, do I need to remove air from the oil pipes? how if yes? thanks
The omp is still electronically metered... the only thing that is being changed here is the source of oil.
This is a great idea but will the car pass emissions in all states because I use two cycle in the gas anyway and i notice that the car smoked a little bit when i did mix in some two cycle and passing emissions is very important in some states

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