Paul;

I inadvertently deleted your e-mail in which you asked my opinion about
how well Tracy’s ECU worked for various conditions.  It basically sets a
base pulse width, and modifies it according to the absolute manifold
pressure (MAP) via the mixture correction table – which is user
adjustable – and can be done via the auto-tune.  In controller ‘A’ of
the redundant controllers, there is also induction air temp correction,
which is relatively minor.  So fuel is delivered as a function of rpm
and MAP, and so automatically accommodates altitude changes.  There is
manual over-ride to adjust the pulse so you can choose richer for max
power or leaner for best economy.  Simple and effective.  Once set up,
it can be run hands off over the entire flight regime, if you so choose.

It uses two mixture correction tables, one for below 3000 rpm, and one
for above.  Since it uses no throttle position indicator (TPI), this is
necessary to handle the case of low MAP, high rpm as in the case of a
descent.  This may not be the most optimum, and can complicate the
tuning, but this is a value priced unit.

I would say that the unit is not particularly “noise” tolerant. I had
much frustration with the unit resulting from spontaneous corruption of
user adjustable settings, apparently unique to my electrical system
design, and in a composite airframe.  Having these changes occur
in-flight was definitely disconcerting. Many attempts at wiring changes,
filtering external circuits, and numerous re-tunings later, the problem
was finally resolved (I believe) just recently by adding further
filtering on the circuit board.

I can’t see any issues with a constant speed prop, except for a
possibility of complicating the tuning of the transition from low to
high table, but since I’m running fixed pitch, that is only a WAG.
Tracy could certainly clear that up.  My particular problems
notwithstanding, I’d say it is a very effective way to go.

Al


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