Chris/David;
.
In our
installation
the primary fuel injectors are in the 500 cc range, where
the
secondaries are in the 1500 cc range
Do you really mean 1500
cc/min? That’s huge. It could make tuning a bit difficult.
Here are some
suggestions for getting mixture tuned based on my experience of re-tuning about
15 times, or more (remember the settings corruption problem I used to have?):
Get your coolant temp
readout working.
Set mixture correction
table to default (all zeros) if not already there. Read the manual again; modes
3, 6, and 9. Also read again the EM2 manual about ‘Mixture Display’
and ‘Editing the MAP Table’.
Normally one would
first set Mode 3, but if your secondary are really that large, you may wish to
go to mode 6 first, turn the Program knob toward the left, and push the store
button a couple of times.
Go to Mode 3 at about
22” MAP. Adjust until the mixture monitor (MM) is about mid range (or
oscillating, which it will do around stochiometric) with the mixture knob at 12:00 oclock.
Then go back to Mode 6
and adjust until the mixture is fairly constant above and below the stage
point.
You could then get a first
pass with Mode 1, but I have found it sometimes simpler to just go to Mode 9;
advance the throttle about 0.5” to 1” MAP at a time, turn the
Program knob to either about 9:00 (if you need to go leaner) or 3:00 (if you
need to go richer) and press the Store button as many times as you need to get
the MM about mid range. At MAP below about 12-13” you’ll want it
richer, so set for the MM to be at or near the top. Continue up until maybe
about 22”. Make sure you keep a stable MAP as you make the adjustment.
You can cut the running time by taking bigger steps in MAP as you go you,
because the idea is to edit the in-between entries from the EM2 with the engine
off.
Then, with engine off, display
the mixture correction table on the EM2 and edit the bars that look out of line
to get a reasonable smooth variation. Look at the trend of the bars approaching
22” MAP and continue the trend up (probably up) gradually flattening out
up toward 29 -30. If the values are going to max or min of the range, you’ll
have to re-set mode 3 to shift the distribution up or down.
Now you are ready to go
to auto-tune. I have found that auto-tune (with mixture knob at 12:00) makes it
too lean for best idle; so I usually start the auto-tune at about 12.5 –
13” MAP.
I
would think an ideal IDLE power setting would
be
where the plane does not require braking to remain still.
I have found that with
my 66” dia – 80” pitch prop my Velocity doesn’t
move until engine rpm is somewhere upward of 1500 rpm.
I get about 5500 static
with my 20B, and about 5600 on takeoff. With adjustable pitch you will want
to get some higher numbers.
Hope you find this
helpful,
Al