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Message
My guess is that it appears that when
closing the throttle very rapidly, you probably end up with an overly rich
intake manifold air/fuel mixture. This may occur because in one
fraction of a second you are opearting at WOT (lots of fuel flow)
and the next down to idle. So the rpm drops down in to the LOW, LOW
range due to the rapid decrease in manifold pressure caused by the rapid
throttle closure and still rapidly pumping rotors. So its down in the
low rpm range with a rich mixture and then since the rpm is so low, the
manifold pressure may well creeep back up to the 16-17" Hg range simple because
there is not enough rpm to keep the manifold pressure lower. So
now the system is seeing higher manifold pressure. Since the
system only really uses the manifold pressure (and not rpm) in its calculation,
the higher manifold pressure convinces itself that you have opened the
throttle a bit (while you actually have not) and so it dumps in a bit more
fuel. This keeps the mixture overly rich as there is really not as
much air coming into the system. Once you crack the throttle a bit, more
air flow leans out the mixture, rpm increases, manifold pressure actually
decrease back to 14-15" Hg and the system stabilizes.
GREAT
explanation!!! That's got to be exactly what's
happening.
Thanks,
Rusty (now
I can ignore that
"problem")
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