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From: "Steven W. Boese" <SBoese@uwyo.edu>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: RE: [FlyRotary] Re: BSFC and EGT
Thread-Topic: [FlyRotary] Re: BSFC and EGT
Thread-Index: AQHNNRdMecGKskb6jkmqr63mscOZtJbQBgfv
Date: Fri, 18 May 2012 21:07:49 +0000
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Ernest,

The base timing for the test was set as recommended in Tracy's EC2 manual. =
 TDC was determined using minimum displacement which matched the front pull=
ey mark.  The manual states that the timing is adjusted by the controller d=
epending on "many" factors.  I did not investigate the controller timing ch=
aracteristics since I had no desire to second-guess or duplicate Tracy's "y=
ears of testing".

Steve

________________________________________
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of =
Ernest Christley [echristley@att.net]
Sent: Friday, May 18, 2012 10:55 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: BSFC and EGT

I think this is going to be useful information, and concurs to what I was t=
aught as a trucker...to save fuel, run slow
and gear high.

  The first step for me is going to have to be mapping the EGT to AFR.  Has=
 anyone done this, BTW?  Is there a direct
and consistent correlation?  Once I have that, tuning then becomes a matter=
 of setting the target AFR in a table of RPM
vs [TPS | MAP] and then running the engine through several power cycles acr=
oss the timespan of a couple minutes.  The
computer will then adjust the fuel injector open times as needed to obtain =
the target AFRs.

One question I have about the data presented is, "What was done with igniti=
on timing?"  If the timing was held constant
throughout the test, that explains a lot about the numbers.  As the EGT dro=
ps off from the AFR increases, the mixture is
taking longer to burn.  You could possibly be getting peak pressure well af=
ter the 50* ATDC that Lynn has called out.
The same would inform the peak heat transfer to coolant numbers.  The heat =
absorbed by the coolant is going to be as
dependent on how long the fully burned mixture stays in the chamber as it i=
s on the AFR.

I can't speak directly to this experiment, because it doesn't mention timin=
g.  An interesting enhancement to the data
generated would be to vary the mixture as before, but to tune the timing fo=
r max power at each data point.  If that was
done, I'd be interested to see what the graph you shared yesterday would lo=
ok like with the timing numbers added.=