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I'm not sure about "suicidal" either, but yes I do
understand why you'd feel that way... That is why it would need to be tested
which should be pretty simple in run-up, etc. Also, I much prefer the
"ARMED" approach. To that end in my Legacy, as most know I'm going to be
beta testing the Vertical Power modules in my Legacy.
I've been talking with the designers about this issue and
they will most likely implement a form of "ARMED" detection/triggering where you
can setup a programmatically rule to address emergency conditions around the
boost pump. This may allow picking the percent power where an abrupt fuel
pressure reading going to zero or below some settable threshold would trigger
the "Emergency Boost mode". It may also allow for automatic triggering of
the boost pump (either low or high) at specific altitudes, etc. Mind
you, these "software features" do not exist today, but the capability certainly
does with their system.
But short of their system, the logical thing to do based
upon what Continental told me, is to determine if HIGH boost causes the engine
to get too much fuel in run-up, etc. Then to determine if there is a
"simple" way to develop a "retro" option to support this concept of
"ARMED". It would nice to know what Columbia uses as the "triggering"
mechanism. It can't be fuel pressure alone as it is RPM dependant (this is
a engine driven pump we are trying to figure out right?).
*WITH NO SPECIFIC KNOWLEDGE*, it does seem that because the
Dukes pump is *pre* the engine, that too much fuel really can't happen, it's
metered by the fuel divider and if the throttle body is not open, then the fuel
is returned via the return line. So in effect you are just pumping fuel
back into the tanks via the return line.... Course like I said, I have no
specific knowledge, just conjecture on how the fuel system works. I do
know tho that some people use the high boost mode to purge the vapor out of the
lines after shutdown or before startup. They simply allow the pump to
circulate cool fuel throughout the lines, which is why I assume that the
injectors can only take a Max amount of fuel and the remainder is shuttled back
to the tanks via return lines...
As I also said, I wish
this wasn't all "black art" and that there was a scientific way to determine the
optimal in all conditions...
Alan
Posted for "Colyn Case on
earthlink" <colyncase@earthlink.net>:
Alan,
I suspect high boost
+ a working mechanical pump on TO would be fairly
suicidal but I can't say
that from experience. (hmmmm......)
Colyn
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