REFLECTOR: Slow idle speed for short fiel landings

steve korney s_korney at hotmail.com
Tue Mar 20 12:54:25 CDT 2007


On my four cylinder Lycoming, I can get it to idle below 350 rpm's....  Talk 
about short field landings...

Best... Steve



----Original Message Follows----
From: "Laurence Coen" <lwcoen at hotmail.com>
Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Franklin engine noise?
Date: Tue, 20 Mar 2007 04:50:15 -1200

Hiroo,

John is right, 600 RPM is too slow.  The recommended idle is in the range of 
750 to 900 RPM.  The Franklin has a large valve overlap which works great at 
high RPM but is terrible at idle.  On engine start I have rough idle at 1000 
RPM but by leaning immediately, the RPM will rise to as much as 1300 RPM and 
things smooth out a whole lot.  If you don't lean for ground operation you 
will foul your plugs.  My idle is set for 750 RPM but warm-up is 1100-1200 
RPM.  750 RPM idle is still rough but 900 RPM makes things tough for short 
field landings.  As far as I'm concerned, landing is the only time you need 
to hit the idle stop.

Larry Coen
N136LC
SE/RG Franklin-IVO
   ----- Original Message -----
   From: Hiroo Umeno
   To: Velocity Aircraft Owners and Builders list
   Sent: Monday, March 19, 2007 4:40 AM
   Subject: REFLECTOR: Franklin engine noise?


   I have a favor to ask for those who are flying a Franklin.

   Would someone able to capture the engine startup, runup, and idling sound 
digitally?  It does not have to be "audio-phile" quality.  Some handheld 
device is fine but preferably with gain set low enough that it does not clip 
due to high sound pressure.

   What I am looking for is.

   Startup, running at 1000rpm, runup at 1700rpm, mag-check, then idle with 
throttle pulled all the way back.

   I am convinced that my Franklin is "missing a beat" but I do not have any 
reference to compare against.

   I finally got mine running again this weekend (changed the ignition 
harness) and it is back to its old trick of growling and shaking. The 
shaking is most pronounced when the throttle is pulled back all the way and 
the engine is idling at 600rpm or so.  You can see the canard tip bounce 
around ½" or so at the tip.  My wife thought that I had some bolts loose.

   Hiroo



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