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My scheme is to have two "Throttle" levers
- a long one to
the throttle and a shorter one to the wastegate. The wastegate would
remain "OFF" or all the way back for ground and pattern operations. Take
Off and initial climb would be with wastegate OPEN and throttle adjusted so as
to not exceed 30" MAP even with the "residual" boost that we would have even
with wastegate open. Climb to altitude (after MAP dropped below 30" at
WOT) and cruise would generally be at WOT and gradually increasing boost
(closing the wastegate - advancing the Boost lever). The first step for
descent would be "Boost - OFF".
You've described the
system I'm flying with exactly. I used the "mixture" lever for my
wastegate, largely because the quadrant was already fit to the fuselage.
If I were choosing from scratch, I'd probably go with a vernier type
cable. The wastegate lever has very little throw, and the most you can get
is about half travel on the lever to go from one stop to the other.
I'm afraid the wastegate adjustment is going to be touchy.
Fortunately for you, I should be able to answer that question in the near
future.
I still have more power available than any NA engine and even if I get
excited and two-block the throttle, I only have a couple of inches of boost -
not enough to damage anything, even at SL.
Don't count on only having a couple
inches of boost with the wastegate open. As I mentioned before, I
have more than 3 psi (I originally wrote this in inches, but it sounded like I
was bragging <g>), and won't know how much more until I can increase
the pressure of the relief valve spring, and go to a safe altitude to test
it. My greatest hope is that I'm already very near the limit, and the
relief valve isn't really having to dump any boost.
If I did away with the waste gate, I would have full boost all the time,
which would, as well as excessive care and attention, involve a great deal more
intercooling (and other heat rejection) than I am prepared to accept.
Additionally, I would be pumping full boost through partial throttle which I
presume to be quite inefficient. It would involve taking off at a little
more than half throttle.
You won't really get boost at low
throttle, even with the wastegate (wg) fully closed. In fact, the
normal wg actuator keeps the wg closed until so much boost is produced that
it needs to open. Having it closed will make the plane a bit quieter in
the ground also. I've opened and closed the wg on my engine at low
throttle, and there's a noticeable change in sound. It's not all that
significant though.
For all the talk, it's STILL ... just a theory .... Jim S.
Not for very much longer
:-)
Rusty (installing a real oil cooler
today)
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