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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "'Rotary motors in aircraft'" <flyrotary@lancaironline.net>
Subject: 88HP vice 130 HP. [FlyRotary] Re: 295cc vs 495 cc Renesis Test[FlyRotary]
Date: Wed, 24 Jun 2009 07:32:40 -0400
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Hi Dennis,

Nice experiment - some useful information for folks to make decisions with
concerning size of primary injector in the Renesis.

I calculated that at your fuel pressure (assuming the rated flows of the
injectors are for 56 psi, I derated the flow 14% for your- 42 psi), that you
were getting approx 507 cc/min total fuel flow at 100% from your two 295
cc/min primary injectors.  This equates to approx 8.04 gallon/hr which at 6
lb/gal = 48 lbs/hr /0.55 = 87.7 HP.  So I do not believe that you were
producing 140 HP - but considerably less.  The RV can fly 0n 87.7 HP once
airborne without any real problem, but I sure would not want to be taking
off on anything less than a 5000 ft strip at sea level {:>)

This is (in my opinion) sufficient reason by itself to have all four
injectors near the same size - or at least have the primary up around 440
cc/min.  That would give approx (derated 14% for lower pressure of 42 psi)
around 12 gph x 6 = 72 lb/hr/0.55 = 130 HP.  That is about what I was making
way back in 1998 when I first flew.  The RV flies fine (but, you won't hit
200 MPH {:>) - my max was around 185 MPH TAS back then)  on that power once
airborne, but take off run on a hot day was overly long - probably close to
2000 feet, perhaps more.

I do agree with your analysis of the engine leaning out once the injectors
hit 100% duty cycle, but believe your power was considerably lower than what
you estimated.  

The average injector flow for injectors shown in the Renesis manual are
Red - 294  cc/min
Yellow - 360 cc/min
Blue - 502 cc/min

Their max flow shown was a bit higher but I took the average.  I presume you
currently have the red primary injectors and blue secondary???


Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Dennis Haverlah
Sent: Wednesday, June 24, 2009 12:26 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 295cc vs 495 cc Renesis Test[FlyRotary]


I've been following the injector thread for a few days so today I tried 
an experiment.  I ran my Renisis with stock injectors (295 Pri and 495 
Sec) on the ground to see how it ran with primary or secondary injectors 
turned off and how much HP I could generate with the 295 cc primaries.  
Note - My fuel pressure is set at 42 psi.

I found I could run around 140 HP ( HP as shown on the Not Calibrated 
EM-2) with the primaries on and the secondaries off.  
I also found that as I opened the throttle above the 100 % duty cycle of 
the primaries the engine would go lean quite rapidly and quit. 
If I were in take-off mode at low altitude and had a secondary injector 
fail I don't believe I could diagnose the problem easily  and keep the 
engine running on the primaries!!  

My theory as to why the engien quits is that as I am running only on the 
primaries and I advance the throttle beyond the point where the 
primaries are at 100% duty cycle the engine starts to go too lean and 
the RPM's decrease - This causes the MP to increase because the engine 
is pumping less air.  As the MP increases the volumn of air in the 
combustion chamber increases.  You need more fuel to compensate but the 
injector is already supplying the maximum fuel it is capable of 
supplying.  The fire goes out and the engine quits. 

I believe to keep the engine running when I have a secondary injector 
fail I'd need to throttle back to some where around 18 inches MP before 
turning off the secondaries and figuring out the secondaries are bad.  
If the engine ran smooth on the primaries I could slowly advance the 
throttle to increase HP as long as I did not go too high MP and get into 
the lean condition.  This is just too much stuff to do at low level just 
after take-off!!

I now plan on replacing the blue 295 CC primary injectors with yellow  
495 CC secondary injectors!!

Dennis H.

>  
>

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