Hello Paul-

Getting ready for 'first' flight again & we've been able to replicate the
engine anomaly that was reported when we had our mishap last time.

Seems that when the engine is running between 4000 - 4500 rpm & the throttle
is smartly advanced, the engine will stumble for ~ 1 second before running
steadily again.  We can replicate this with no problem -- it happens every
time.  If the throttle is slowly advanced, the engine smoothly increases in
rpm with no hint of a stumble.  We also tried this with the mixture set full
rich -- stumble seemed worse / longer, and with full lean -- stumble seemed
less, but did not go away.  If the engine is running below the 4000-4500
range (say 3000) and the throttle is smartly advanced to WOT, the stumble
doesn't seem to happen.

We tried to track the MAP values to see if anything seemed odd during these
tests.  Unfortunately, it seems we've developed an electrical problem with
either the EC2 or the EM2 -- they're not talking to each other, so we had no
way of displaying what was going on as the engine ran.  We spent a while
debugging that issue & ruled out obvious causes.  (Tracy suggests we check
for good ground between the two devices & it that is solid then they need to
get sent back for testing).

Do you suppose this behavior (the stumbling) just means we have more MAP
adjustments to make (once we get the electrical issue sorted), or could the
slide throttle implementation have anything to do with it?  Just trying to
eliminate things to be checked...

Thanks,

Mark & Terry

Move the throttle slowly :) Let them eat cake :)

Does it happen during injector staging when the MAP is around 15 inches of HG?
Making it richer in that area should fix it. Perhaps making it leaner as you already tried richer. It should have nothing to do with the throttle as you are measuring the MAP inside the rotor housing. Carbs handle this problem with an accelerator pump which temporarily richens the mixture. EFI's uses a throttle position sensor but Tracy does not like those.

My C182 engine will stumble if you slam the throttle open. No accelerator pump on the carb. At least I don't think there is one.

Paul Lamar