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Date: Tue, 17 Jan 2012 15:39:12 -0500
From: Chad Robinson <crobinson@medialantern.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
CC: Ernest Christley <echristley@att.net>
Subject: Re: [FlyRotary] Re: tuning advice
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A little Googling turned this up:
http://www.esnips.com/displayimage.php?pid=8400208

On 1/17/12 2:31 PM, Ernest Christley wrote:
> 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
>>
>>
>
> --
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