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


Paul,
this is why automotive ecu's have a throttle position sensor. The computer
uses the injectors as the accelerator pump by increasing the pulse width
momentarily above what the map has given.
I don't think Tracy's unit supports this, but being gentle with the
throttle
does.
Larry


Mark, set the data acquisition system to 2000 samples per second and
monitor the
pressure at the output of the pressure taps on the rotor housings.


Paul Lamar

I think the problem lies with your MAP table addresses. There are two MAP
tables in the EC-2, and it switches between them based on RPM and maybe some
other factors.

I had the same phenomena at a lower manifold pressure, and diagnosed that it
was caused by switching between the two tables.

As you advance the throttle slowly, the manifold pressure rises slowly, and
you can program the EC-2 to smooth operation. When it switches to the second
table, you don't notice the effect.

when you rapidly advance the throttle, the manifold pressure changes
rapidly, and enters a region of the table where you HAVE NOT tuned, because
you can't get to those conditions by slow advance of the throttle. So, the
engine either bogs or leans out and hesitates. when it gets above the rpm
point, then it is reading the table in the region where you have tuned and
it smoothes out again.

The solution, edit the values around the bog/stumble rpm/manifold pressure
in BOTH tables to be the same value. Then when you rapidly advance the
throttle, you will keep the correct mixture. Made all the difference in the
operation of my unit.
Bill Schertz
KIS Cruiser #4045
N343BS
Phase I testing


Sounds like the problem Bill. This is the staging area and it happens at 15 inches of HG according to Tracy.

How many hours do you have on the KIS so far?

Paul Lamar