REFLECTOR: Franklin engine noise?

[Laurence Coen]

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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