It also might be a couple of bad addresses in the area that can’t be tuned
while not in flight. If the throttle change is rapid, the EC2 may change to a
manifold pressure in the high rpm table that is not yet been adjusted.
Ok, 3" would not likely be causing this problem.
It may not be a restrictive manifold pressure sensing line
- but, if its easy enough to take the restrictive plug out of the line, I would
give that a try.
Some folks put a restriction in to damp or smooth out the
manifold pressure pulses - but, if too restrictive can delay the EC2 response
to manifold pressure changes.
Ed
Sent: Wednesday, February 22, 2012 8:37 AM
Subject: [FlyRotary] Re: Throttle Back Bobble
Ed,
I have the Mistral intake. I do think we put a restrictive plug in the
pressure line. Not sure why we decided on this as it was, IIRC, recommended by a
buddy that was formerly very involved in the project. I will check tonight if I
make it out to the hangar.
I am not sure what the diameter, however, I think the turbo duct to it is
three inches.
Thanks.
Chris.
Sent from my iPhone 4
What size throttle body do you use (diameter or type),
Chris?
What I would speculate (and this is all it is) is
that when you throttle down suddenly - the engine manifold pressure drops
rapidly - IF your manifold pressure sensing hoses to the EC2 are too small or
there is too much damping of the manifold pressure signal for other reasons,
then your engine could be down operating at lower manifold pressure while your
fuel injector is still calculating fuel for the higher manifold pressure it is
still seeing. So your engine could be running overly rich for a period
of time.
Throttling down slowly gives the manifold pressure read
by the EC2 to adjust to the engine manifold pressure as it is slowly reduced
and you avoid the mismatch due to manifold pressure differences.
There could also be some mismatch between your fuel map
and operational needs. But, again these are just guesses based on the
limited amount of data.
The easiest way I know to check the manifold pressure
sensing possibility is to try putting on larger manifold hoses running to the
EC2/3 or removing any damping cans or such..
Ed
Sent: Tuesday, February 21, 2012 10:53 AM
Subject: [FlyRotary] Throttle Back Bobble
When I throttle back on my otherwise smooth running
13b turbo, I tend to get a bobble (miss?) as the
engine spins down. I don't seem to have it if I throttle back very
slowly and smoothly, but fast moderate (usual manner) or quick throttle
back produces it. I have noticed this on Lycoming's
if throttled back quickly, but obviously not an issue that I
have noted in a regular car engine.
Just curious if others have had this occur and if so why.
The list has been especially quite lately so come on folks, here your
chance to shine before I start calling DAR's
;-)
Chris
Houston