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OMP Oil Metering pump output and modification

Old 04-11-2019, 09:28 AM
  #101  
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Brett,

I really can't say what will work for your setup, other than maybe the actual oil type is not best for your fuel when using omp. I believe you were using crankcase oil, and that may be the only issue when you switched fuels. I have read that the guys who run heavy alcohol fuel content here in the states use a castor based 2 stroke blend, because it stays in suspension in alcohol fuels longer than esters or other blends. This effect may also occur on lubricated surfaces within the engine as the alcohol washes away the petroleum based oil within the chamber. I think your problem may not be (only) oil delivery system here but oil type primarily.Crankcase oil is a terrible lubricant in my opinion in a total-loss system like we have.

If you could get a Sohn on your engine and inject a castor blend, I bet your results would be acceptable with the omp again.

I have found that premix rate directly affects oil blowby into the crankcase much more than omp injection rate does. I think there is a point in the combustion cycle that the fuel injectors really have good access to leakage areas on the side seal and oil seal systems, and the pressurized mixture goes through it in quantity. Fuel too, but that will evaporate to some extent. We have all heard about the modded turbo FD guys complaining about 10% fuel dilution in 1000 miles of running,and crazy stuff like that. That is not solely attributable to a worn engine in my opinion.

In my stock NA setup, I just run oil level lower when changing, so it has room to "grow" during the interval. If you look at my oil analysis submissions posted on this site, there is evidence
of oil dilution by oil. My choice of a thicker sump oil reflects this reality too. I bias my choice of oil toward getting the chambers a lot of lubricant, and what happens to the sump oil is a secondary concern. My wear numbers show pretty good results at this point, so I think I am satisfied with the compromises. I like the OMP, but just with greatly increased output. For you, i think it would be better, but the lubricant choice is very important. Redline and Klotz sell 2 stroke alcohol oils, and are talking about 12:1 or 16:1 oil ratios on their websites! Sounds to me like fuel type leading to oil type is your primary problem, followed by oil quantity. Model airplane oil is in your future!
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Old 04-11-2019, 03:14 PM
  #102  
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Thanks Kevin , some good info there! I'm going to try 120:1 instead of 100:1 to start with and see if that slows down the level rise. Most of the REW guys run that for the street . I wanted to run a higher ratio because I think our exhaust ports need extra but I'll just do that for dyno/track day if 120:1 works out.BTW I'm already using Motul 2T micro, which is a model airplane oil ...so you are 100% on the money there !

Very interested to hear that you get an oil level rise now that you have upped the omp rate dramatically. I'm thinking that at low rpm/load the oil doesn't get burned off and accumulates in the chamber if there is too much coming in . then there is only one place for it to go ..... into the sump.

Last edited by Brettus; 04-11-2019 at 03:32 PM.
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Old 04-11-2019, 10:41 PM
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Brett,

Actually as I reduced my premix ratio, I was upping the OMP output. I reduced my premix ratio to about 1/3 of what it was before and saw an immediate and large decrease in "sump seep". I didn't measure it and its strictly anecdotal, but the premix was largely what was ending up in the sump, in my view. I am running approximately the same overall ratio approximately, combined with OMP and premix as before, just the OMP has the vast majority of the oiling duty, and my sump seep is much less than it was. So, my theory is that the OMP is much more efficient at delivering oil to the chambers, where it will leave via the exhaust port instead of oil seals. There is a lot of oil being burned in my engine, (by current standards), by my choice, and I now prefer the OMP to do most of the work.
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Old 04-14-2019, 01:23 AM
  #104  
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Originally Posted by Delmeister View Post
This pump is the most ingenious electro-mechanical device I've ever come across. Some years back I acquired a used one and studied it in detail..

It really should be included in this thread

https://www.rx8club.com/search.php?searchid=13452228
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