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Re: [LML] LOP vs ROP Climb: Time and Fuel Burn (LIVP)
A year
or two ago, Aviation Consumer wrote an interesting article on MP v RPM and
what was the best tradeoff between friction and cylinder pressures. The
consensus, as best these things can be known, what it was better to operate the
RPM at a higher level, than low. The friction loss associated with the
higher RPM was offset by the reduced peak pressures such that the wear and tear
on the engine is less at 24 x 25 than 24 x 24 and certainly better than 25 x
23.
So, if
you are going to reduce power, between MP or RPM, it is better to reduce MP
since higher RPM keeps PP lower, at least that was their general conclusion,
supported by engine shop experience.
Thanks,
Chuck Jensen
Diversified Technologies
2680 Westcott Blvd
Knoxville, TN
37931
Phn: 865-539-9000 x100
Cell: 865-406-9001
Fax:
865-539-9001
cjensen@dts9000.com
Jeff,
that's interesting. I wonder why you get
those high temps.
I wonder what is different in our engine
setups.
my CHT's are steady @380 in the max/max condition
@140knots.
It's been tested to 20,000 in that
config.
CHT's get better than that with less power
or more speed.
I have exhaust tunnel extensions which seem to
make a huge difference for cooling.
also have ceramic coated exhaust. I don't
know how much of a factor that is.
Some will say that 2700rpm is a bad idea because
of higher friction losses.
On the other hand the flame front always moves at
the same speed so if the
crank is turning faster your theta pp (angle
after top dead center where peak pressure occurs) is bigger
and the peak pressure is less. ....which
seems good for everything. the pulse on the crank
is not as concentrated, the CHT's are
lower. assuming everything else is setup right.
Colyn
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