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Date: Sun, 21 Nov 2004 20:47:40 -0500
From: Mike Robert <pmrobert@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: MMO vs 2-cycle    (was  Re: how do you carry,
 and measure oil?)
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Russell Duffy wrote:

> Just curious, is this increasing oil level we find using pre-mix only 
> happening because we run such high power all the time?  I just spent a 
> dizzying few minutes searching the RX-7 list for any mention of this 
> phenomenon, and couldn't find one.  Neither of my previous RX-7's (85 
> and 93) ever showed any sign of increasing oil level.  The 85 injected 
> oil at the carb, so it would be similar to pre-mix.  The 93 was oil 
> injected, but I also added 4 oz MMO per tank, so there was some pre-mix. 

Rusty, I daily drive a street ported 12A fuel injected 83 RX-7 premixing 
marine 2 stroke oil 1:128 and do observe scavenging of the premix oil 
into the sump. I (and many other much smarter people than I) think that 
1:128 is an excellent ratio for high power settings but anything less 
than high power settings will scavenge the premixed oil into the sump. 
Personally, I change the sump oil when it's at the "full" mark - at oil 
change I fill to halfway up the stick. I'm fairly certain that 2 stroke 
premix oil is not the best lubricant for plain bearings so change when 
there is a significant amount in the eshaft sump. This report is 
courtesy of My Gut Feelings and anecdotal evidence from people who I 
fully trust. This polarizing issue gets brought up on rx7forum.com every 
now and then and usually turns into a giant flamefest with the concept 
of premix->sump oil scavenging taking on the properties of UFO or 
Sasquatch viewings. All I know is that my car does routinely end up with 
more oil in the sump over time. I have no OMP due to the difficulty of 
fitting the pump linkage to the TBs so all rotor seal oil comes through 
the fuel injectors. I have 15K+ miles and couldn't be happier.

> Rusty (finally off to see if our latest part actually works)
>  
>  

Good luck!
    -Mike