Dave, see my 0.02 worth in blue below.  At 30 seconds at a time, you still have a ways to go to match my 14 minutes of rotary glider time {:>)

 

Ed

 

SNIP

 

 

 the bad news.  It became very difficult to run lean of peak with the
lack of an automatic waste gate actuator.  Since boost is very dependant on
RPM, even the small of pitch changes required to maintain level flight
caused enough variation in RPM to significantly change the boost - i.e. slow
down just a little, boost drops, less RPM, less boost etc.. and in about a
second the engine quits running.

 

  Slightly increasing the mixture is not
enough to get it back as by then the RPM s have really dropped.  It usually
took a significant increase in mixture to start the engine again.  I'm even
starting to get used to the sensation of my engine stopping (watch out Ed,
I'm gaining on you in glider time). 

I think, Dave, you are once again pointing out the risks and difficulty in trying to maintain boost control through throttle control alone.

  Here is what I think what may be happening -  a rapid feed back situation. Without the boost gate and using manual throttle control  you have no "reserve" of exhaust mass flow.  In other words, with a waste gate you could be dumping say 10% of your exhaust mass through the gate.  So   a slight variation in exhaust mass flow caused by varying the aircraft attitude (and rpm)  could be handled by the wastegate system without your knowledge.  As the massflow started to slow, it simply stopped dumping as much (or any) through the gate.  This kept your boost stable and therefore the air/fuel mixture control could be leaned (you would loose some mass flow - but hey! you were dumping 10% of it in any case).

Now you disable the waste gate and go to manual control of boost by the throttle.  Here YOU must adjust the throttle and mixture control precisely and exactly to maintain X level of boost.  There is no exhaust mass flow reserve like you had with the waste gate.  You are exactly at the state where throttle and mixture produce X psi boost.  Now,  the attitude of the aircraft changes causing the engine rpm to drop slightly, this results in less mass flow - but now you have no reserve mass flow.  Mass flow drops, turbine wheel slows, boost drops, manifold pressure decreases all of this results in even less mass flow which causes more boost drop, etc.,etc.  A feed back situation that can quickly cascade into power decay rapidly when using manual throttle control. 

I am not certain why the fuel mixture gets out of whack. I would think if you waited long enough (30 sec?) the system would stabilize and the E2 catch up with the current state and everything would start running again.  I suspect that under boost the EC2 is of course providing gobs of fuel to go along with the high air mass flow (represented by high RPM and BOOST).  Suddenly it finds the the boost all gone or greatly decreased, in fact without the boost the manifold pressure may plummet very sharply.  The EC2 may simply in effect shut off the fuel flow due to this rapid decrease (same effect as if you had closed the throttle quickly). 

Tracy, of course, would be the one to ask.  This is just my 0.02 worth

 

Ed Anderson

 David Leonard
The Rotary Roster
http://members.aol.com\_ht_a\rotaryroster\index.html
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