Benefits of premixing/ 2-cycle oil reservior feed revisited
 

As mentioned on here in other threads, I had been using a modified oil metering system on my '85 GSL 12A. I bought this car four years ago with an odometer reading of around 123,000 miles. (if odometer readings on 18-year-old cars can ever be trusted). The 2-cycle oil feed system was installed in the first month that I owned the car.

After running the mileage up to 163,000 miles (approx. 261,000 km) the engine finally gave up the ghost---- compression on the rear rotor dropped to near zero and the car ran only on the front rotor. This was in March, and I finally found the time last month to tear down this engine to evaluate the situation. (I've since parted out the car--- it had been rear-ended and was therefore not worth restoring--- and bought an '84 GSL 12A in nicer shape).

The cause of the failure turned out to be severe flaking of the chrome liner of the rear rotor housing--- large sections had dissappeared out the exhaust, causing the apex seals to chatter as they scraped along what was left of the chrome.

This flaked chrome had probably been axacerbated by the fact that the high-mileage engine had (by this time) worn oil control o-rings, which allowed more oil into the combustion chambers. This excess oil acts as a lifting agent and will actually work its way in under a chrome surface that has started to flake around the edges. From there it's only a matter of time before large sections get spat out the exhaust, usually in one catastrophic event.

Compression was already not as good as it had been due to corner seal springs that had lost most of their spring. However, the irons showed very little wear and are well within Mazda's published wear limits. Even the original factory machining and nitriding is still visible on most of these surfaces.

But the reason for this thread is the over all clean and functional condition of the apex seals, side seals, corner seals and their associated springs, as well as the relatively small amount of carbon build-up--- a condition that can only be attributed to the benefits of using cleaner-burning and build-up reducing 2-cycle oil in the metering system rather than the crud from the oil pan.

In spite of the flaked rear rotor housing all seals were intact and functioning perfectly. All springs worked freely, albiet the corner seal springs were weakened and no longer doing much.

Usually when these engines are run for many tens of thousands of miles after the oil control o-rings have begun to let excess oil into the combustion chambers the result is large deposits of carbon on the rotors and plugged into the seals, rendering them stuck and non-functional. The fact that mine showed none of this clogging speaks well for the benefits of pre-mixing or using a 2-cycle oil feed.

Good to hear ! Do you mix at 100:1 ratio ?

Interesting. I've been premixing about 8-10oz. of 2-cycle per fillup for several years in my 4 rotaries, but I left the OMP connected, figuring it couldn't hurt, but now I wonder.

any pics? what are you using to hold your 2-cycle oil.

100: 1 is (I believe) the ratio that most pre-mixers use, but I used a modified metering pump that acted as a block-off plate to keep engine oil from being fed to the carb. Instead, a separate reservior fed the metering pump via gravity. The metering pump fed the carb with the same volume of oil it always had, except that it was feeding clean (and cleaner-burning) 2-cycle oil rather than the dirty 4-cycle stuff from the oil pan.

No pics unfortunately, but the system is really simple: get an impervious-to-oil canister (an old power steering fluid reservior works well) and mount it up high on the RH shock tower.

Run a length of fuel hose from the bottom of the reservior to a custom-fitted nipple on the metering pump so that the 2-cycle oil can drain into the inlet side of the pump.

Fabricate a block-off plate from a beer can (or other sheet aluminum) and sandwich it between two metering pump gaskets and then place these between the pump and its mounting pad on the engine. This blocks oil flow from the engine to the pump, but allows the pump to continue working just as it always had. It's that simple.

I bought one of those block off plate adapter things to install between my OMP and the motor, but I have not installed it yet. The guy that I bought it from said that I should modify the OMP to pull the max amount of oil (i.e. full throttle amount) at all times. Is this a good idea? Bad idea? Will my car resemble a dirt bike with a constant smoke trail? Heh.

Right now, I'm running the stock OMP with the actuation rod, but as soon as I get ahold of a resevior tank, I will install the new stuff.

Search "Oil Metering Options" by Drunkclever. You will find alot of information how to do it with pictures. My set up has now been in place on my FC for about 5,000 mi. and works great. I use Golden Spectro. Good luck.

When going to the direct drive pump, the mop system becomes rpm based, as opposed to throttle based with the mop rod. Your friend is wrong.

What do you think of the PCV OMP kit?http://rotaryaviation.com/oil_inject...p_adaptors.htm

i ordered that adapter. it was pretty easy to install, and i used a catch can mounted on the shock tower to hold the 2-cycle oil. my engine didnt run for very long after i attached it but i dont think it was because of the omp system. (it had 184000 miles on the odo. and i was the 3rd teenager to own it, lol) i havent taken the motor apart yet to find out exactly why it lost compression but i have dismantled 2 jy motors that had had their omp's blocked off to find that the housings seemed much less worn than the others i have taken apart that still had the omp's attached.

He's not a "friend", he works here: http://rotaryaviation.com/oil_inject...p_adaptors.htm

The same place that I bought it from...

Will the R.Aviation omp kit be RPM based? I dont even have the rod, and I've always wondered how much oil the RA adapter will feed the housings.


right now I'm premixing with the OMP blocked off, but it's a pain in the ass to add oild every fill up.

Edit: I just read clean85's post. I guess it does stay open full time.

I may need to go back and look at the RA adapter, but I was under the impression that it replaced the MOP entirely and the the mop rod was no longer connected to the carb or TB. If that's the case, then the RA pump becomes rpm based as there is a drive gear inside the front cover and no lever to meter the mix based on the throttle position. If it mounts in between the front cover and the mop, simply to supply premix and block off the engine oil, then I am wrong as to how it works. But I like my idea better.

As far as the excess oil causing the chrome to lift, I have doubts about that. There is a very strong mechanical bond between the chrome and the housing liner, I can't see oil breaking it down. It should have the opposite effect and provide a layer for the seal to pass over the edge where the flakeing is. The only possible way the oil could accerbate the flaking is if the apex seals and combution gases were forcing the oil under the chrome, causing delamination. Flakeing begins as chatter marks and progresses from there. Main cause of chatter marks is over reving and lack of lube, the apex seal pivoting in it's groove is also a cause to a lesser degree, but that effect get worse as mileage on the engine increases.

i may be wrong but i thought the RA kit just blocked off the inlet from the front cover and would still be sending oil in relation to the rod connected to the carb/tb. i really want to do one of these mods as i think itll greatly increase engine life. i just need to figure out which route is the best to take.

The Metering Pump Adapter, as offered by PCV Technologies takes the solution one step further in allowing to still using the stock metering pump but supply it with two-stroke oil. This adaptor pump is installed in conjunction with the stock oil metering pump.

It says there you still use your omp.

Hmmm, sounds like I had it pictured in my head wrong then. I wonder why they suggest keeping the mop lever fully open/up then?

I didn't get it either, really? He suggested it to provide maximum lubrication, but I don't want my car smoking all the damned time.

Maybe he was thinking about for race applications?

I guess we should call and ask.

Nah, that's to simple. lol

I have been looking at the RA system for years. I called down there last week to determine which I need for my 13B in an '81. Anyway, I take it that the mop lever "on" all the time will result in it running at 100:1 ratio whenever the engine is running (to effectively mimic yet replace premix).

But what do I know. Will anxiously await the outcome before I place my order.

BTW... got a nice Mazdaspeed catchcan to use as a reservoir on ebay last week. Quality seems very nice.