flyrotary@lancaironline.net Mailing List Archive

Changing the subject a bit, I want to make sure i have my motor on TDC to set my timing marks on the flywheel. This is my plan, tell me what you think. I'm building a fitting to screw in the spark plug hole, and running a vacuum line to a small suringe (like a insulin suringe). I can eyeball the rotor location close to TDC, the install this contraption and rotate the motor so the suringe moves out to the end and starts back in. then back the motor up again till the suringe tops out. I figure that outa be and accurate TDC. Whadda ya think???

Bob Mears
Supermarine Spitfire

-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, 19 Sep 2007 1:16 pm
Subject: [FlyRotary] Re: Strange Ignition?

I do not believe that is a significant factor, either, Al. After all, we're suppose to do our ignition checks on the ground before take off {:>). My understanding is that best power on the 13B has ignition timing between 25-28 deg BTDC, so not surprising that the 20B would fall in that range also. Sounds reasonable to me.

----- Original Message -----

From: Al Gietzen

To: Rotary motors in aircraft

Sent: Wednesday, September 19, 2007 3:08 PM

Subject: [FlyRotary] Re: Strange Ignition?

I wondered if perhaps one issue was that I was doing the ignition check static, on the ground; where the combination of RPM and MAP would be different than in the air. But on checking with Tracy’s spreadsheet on the timing settings, over a fairly broad range above about 4900 the timing is (should be) in the range of 26 to 28 degrees BTDC.

Al

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