I have no flight time on a 914 as of yet. Do have a pretty good
understanding of the Bing type 64 though.
Go up in altitude and the mixture will richen up which = more fuel burn
for a given power setting compared to sea level.
The constant depression carbs are somewhat altitude compensating, but not
complete. Turbo in boost is more compensating than normal aspirated.
Once flying I will be able to tell pretty good numbers on fuel flow as to
just how much thin air richens mixture at given RPM/MP.
I have a fuel flow gauge, EGT, O2 sensor that drives a Mixture Monitor and
ability to lean things out.
Looking at color of spark plugs is not absolute as far as mixture. If you
want the best tell of mixture from the plugs, you need to be hard on motor
and turbo, and your skill of flying if a short wing mono with a right
quartering tailwind:
Run at desired power setting and altitude for a while, then shut motor off
right away and land deadstick without touching throttle position upon shut
down.
When you change throttle position, power setting and altitude things can
easily change and interfere with your good read of plugs.
I am somewhat of a motorhead, don't like to put undo stresses on motors,
so am going with ability to fiddle and test without hurting anything.
If you really wanted to be extreme precise on getting mixture just so,
measure carbon monoxide of each cylinder as per Rotax instructions for
making sure the leanest cylinder is rich enough for full throttle, just
vary a bit for cruise settings. They recommend such a test if you modify
the intake system of a 914. IMHO installing a intercooler is modifying the
intake system. Eastwood sells just such a measuring tool.
Ron Parigoris
|