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I
certainly bow to greater authority on this. Although I suspected OAT diff
might have accounted for this, I talked to a Unison insider who suggested
something about better flame propagation with thier Iridium plugs, and therefore
more efficient burn of fuel in the cylinder. Would have suspected this
would have raised the CHT's, however, if that were the
case....
Doug
Doug:
**Of
interest, within the limits of my setup (VM1000, all altitude and engine
parameters the same with the exception of a 15degF cooler OAT) I did notice a
20-30degF cooler CHT with the new Iridium plugs over a broad range of fuel
flows, and a 2-3 knot improved speed at lean-of-peak operations (no change at
ROP operations).**
I know of no
scientific reason that the type of plug making the spark could make such
differences. It's more likely the OAT. More O2 molecules for combustion and
better air cooling. The improved LOP speed is O2 increases in the cooler air.
It allows for more FF at a given LOP setting. If you were to set the same FF,
the HP output and TAS would be the same. We must be careful to assign the
correct cause for an observed change.
Walter
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