Mailing List flyrotary@lancaironline.net Message #54386
From: Bobby J. Hughes <bhughes@qnsi.net>
Subject: RE: [FlyRotary] Exhaust obstruction test
Date: Sun, 27 Mar 2011 12:32:53 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Steve,

 

Thank you for conducting this test. The attachment contains the data my Advanced Flight Systems engine monitor captured. It logs in five second intervals. A lot can happen in five seconds when the pilot is throwing switches and opening and closing the throttle. The data shows I did not re-enable the primary injector switch until after landing. So no rpm or fuel flow data was captured during most of the glide. Oil pressure indicates the prop was driving the engine. I don’t remember if I bypassed part of the super charger flow or not.  The manifold pressure before the event was only 36” MP so I was not a full power. The rpm dropped from 6700 to 2500. Manifold pressure started dropping but I’m sure I was pumping the throttle and may have pulled the super charger bypass. What I don’t understand is the last seven lines of data. MP is between 18 and 29.4 at idle. This is while I was trying to taxi but could not move the plane.

 

Your data supports a sharp drop in rpm.  Is the MAP  plot EC2 fuel map or manifold pressure? If manifold pressure your test also indicates a high manifold pressure with a low rpm condition.

 

Bobby


From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese
Sent: Saturday, March 26, 2011 9:31 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Exhaust obstruction test

 

Bobby,

 

A plot of data collected from my engine stand with a butterfly valve to restrict the exhaust flow is attached.

 

The MAP was taken only to about 16” rather than full throttle before starting to close the valve.  I tried to close the valve gradually and opened it rapidly.  The valve didn’t seal perfectly since I couldn’t kill the engine completely, but it was still pretty effective.  The EGT’s didn’t drop until the valve was almost as closed as I could get it and at no time did they rise until the valve was opened. About 22 psi of exhaust gas pressure was developed with the valve closed.

 

The engine did not run smoothly with the valve closed but there was no popping.  Remember that this is with a 13B with the peripheral exhaust which may behave somewhat differently than a Renesis.

 

Steve

 

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