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Date: Tue, 17 Jan 2012 14:31:18 -0500
From: Ernest Christley <echristley@att.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: tuning advice
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If you haven't done it, spend some time with "Rotary Engines" by Kenichi Yamamoto.  Lynn sent out a link to it in 2008,
but I downloaded and started reading it on the treadmill last week.  The first chapter is some interesting history.  The
second is a lot of math, that some may find interesting.  I just skimmed it.  But starting in Chapter 3, it gets REALLY
interesting, and explains how a lot of these factors affect one another.

In particular, it explains what it calls a 3:3 burn pattern when there is a lot of overlap.  The first time around, the
three chambers have fresh charge, so they burn normally and produce power.  The next time around, the exhaust gasses
push back the fresh intake, to the point that the mixture won't burn.  So you get three unburnable charges.  The next
time around you get some mixture of unburnt charge from the previous, burned gasses from two cycles ago, and new mixture
from the current charge.  If that actually fires off, the next cycle will have an overload of burnt exhaust, and won't.
 Then it all repeats.


Lehanover@aol.com wrote:
>  
>  
> In a message dated 1/17/2012 6:47:41 A.M. Eastern Standard Time,
> msteitle@gmail.com writes:
> 
>     Lynn, 
> 
>     Thanks so much for a very detailed reply.  It sounds like the
>     factory EC-2 setting for advance will be pretty close for cruise
>     (5200 rpm) mode for my p-port engine.  I usually lean pretty
>     aggressively, so maybe a couple of degrees would be in order.  
> 
>     Can you tell me if its normal for the MAP to be different for p-port
>     engines, particularly around idle (1800 rpm)?  My MAP readings are
>     approx. 17.0 - 17.3 at idle.  This is about 2" higher that with my
>     side-port engine.  I'm thinking this is because of the much higher
>     intake/exhaust overlap with the p-port engine.  
> 
>     Thanks,
>     Mark
> 
>  
> Everything affects everything, all of the time.
>  
> So where the side port can have less overlap, or even no overlap in the
> case of the Renesis, the Pport has a lot of overlap. So, the Pport is
> easily affected by exhaust system and muffler design. At any particular
> RPM a wildly differing set of factors plays out inside the engine. The
> most obvious is the exhaust gasses re-entering the chamber diluting the
> intake charge, and making it over rich (because some of the oxygen
> bearing charge has be displaced and the fuel delivery has remained
> unchanged. This whole scenario may change just a few RPM up or down the
> range.
>  
> So you might get it idling really well today, and in the morning it
> barely runs at all until the oil temps come up a bit. What could cause
> that? The cold rotors are condensing fuel back into droplets, which
> makes for less surface area to mate up with any oxygen, and the engine
> is now very much over lean. Everything affects everything.
>  
> If you have fiddled with dirt bike engines, this all comes to be very
> clear. There is a similar interaction between intake design and exhaust
> design in a piston port 2 cycle engine.
>  
> Notice the strange mufflers on those bikes. A seemingly over sized
> muffler ending with a very small tube that seems far too small to make
> any power. And still it works.
>  
> The rotary is a 4 stroke Otto cycle engine that tunes like a 2 stroke
> dirt bike engine.
> Less so for little or no overlap. Much more so for lots of overlap like
> the Pport.
>  
> So, it will never tune up in idle quite as well as a side port. But the
> higher the idle RPM you can stand the better it will be. Another factor
> that removes the engine from its car like idle, is the fact that the
> prop load is higher than the engine would see in just stirring up trans
> oil at idle. So instead of say 3 HP required to idle you may need12 or
> 15 HP to spin that prop even 1,000 RPM.
>  
> Your first Viking departure will make it all worth the trip. 
>  
> Lynn E. Hanover
> 
>