We
have recently tuned the Ec2 on a 20B & although it
has
helped it run a little smoother we still get alot
of
roughness & surging at idle from 15 to 18 inches
Mp&
especially when pulling back power Has anyone
experienced
this problem? The plane has been run on
the
ground, however the problem was just as bad in air
in
a descent.
Lou
& Paul N ES 117ES
Lou;
You’ll probably need
to spend a fair amount of time tuning, with an O2 sensor readout. But my
first question is about the MAP. MAP at idle ought to be more in the 10 –
11” range. Second question is have adjusted the mixture knob when
it is surging to see if it can be improved. Surging is most likely with a
too lean mixture.
The transistion from
the ‘low’ to ‘high’ table at 3000 rpm on my 20B occurs
around 13.5 -14.5” (table entries 7-9). Tuning in the transition
region needs to be good, or it will cause surging as it transitions back and
forth. Also; if the 3000 rpm transition gets close to the staging point,
it can get really messed up if the tuning on across the stage point is not well
set. I found that moving the stage point up to about 17” helps stay
away from that problem.
I found that I could
not get smooth running below about 1500 – 1600 rpm when running on the
primary injectors (in the housings). It idled much better down to about
1000 rpm running on the secondary injectors that are out at the throttle body.
In my case, that puts them about 8-9” out from the ports; so either the
distance, or the MSD injectors, makes the difference.
If you find it runs better
on the secondary only, there is a simple change to make. In the 20B
version of the EC2, with the external staging relay, you can do what I did and
put the stage relay in the primary power circuit so it runs on secondary only
at low MAP; and the primary kick in above the stage point.
Hope this helps.
Best of luck.
Al G
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