Figuring out what affects my speed

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%. This is harder than most of
us would be willing to run at 5000 ft. Peak EGT at this power setting
is also asking for engine detonation.

Paul kgyy writes:

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%.

OK. That sounds like enough to account for the difference in speed
(?).

This is harder than most of us would be willing to run at 5000 ft.

My virtual funds are unlimited, but in real life, with a limited
budget, I'd be far more conservative.

Peak EGT at this power setting is also asking for engine detonation.

I haven't noticed anything, but I don't know if this is simulated (and
I'm not even sure that it occurs to a significant degree, as there
seems to be a lot of disagreement on that).

--
Transpose mxsmanic and gmail to reach me by e-mail.

Mxsmanic wrote:
Paul kgyy writes:

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%.

OK. That sounds like enough to account for the difference in speed
(?).

The power chart in your POH should tell you how to adjust the manifold
pressure for nonstandard temperature conditions.

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%. This is harder than most of
us would be willing to run at 5000 ft. Peak EGT at this power setting
is also asking for engine detonation.

I might have to read ordinary threads while his sim is getting new
cylinders.

Peter

Paul,

under standard temperature conditions
(15C?).


5 C, actually. 15 is standard on the ground. You lose 2 per 1000 feet
in a standard atmosphere.

--
Thomas Borchert (EDDH)

Peter Dohm wrote:
I might have to read ordinary threads while his sim is getting new
cylinders.

Hopefully the motherboard is still under warranty.

Paul kgyy writes:

The power chart in your POH should tell you how to adjust the manifold
pressure for nonstandard temperature conditions.

It says maximum cruise power at 20° rich of peak, 25" MP, 2500 RPM,
for minus 20 degrees OAT, with the best listed performance at 6000
feet (approximately 200 KTAS), although I'm at 5000 feet because I'm
IFR and that's not on the chart. That's about what I'm getting now
(211 KTAS with the same settings, as close as I can get them).
Economy cruise is about 40 kts slower, but I have virtual cash to
burn.

The cold air doesn't help performance, according to the POH chart.
Maybe it's the adjustments I'm making; I've only recently started
adjusting mixture and prop myself (I used to let the sim do it).

--
Transpose mxsmanic and gmail to reach me by e-mail.

Peter Dohm wrote:

Probably the temperature. At 25" MP and 2520 rpm, I'd guess you would
be running about 78% power under standard temperature conditions
(15C?). But at -1C the denser air is giving you additional power
output so you're probably closer to 80%. This is harder than most of
us would be willing to run at 5000 ft. Peak EGT at this power setting
is also asking for engine detonation.

I might have to read ordinary threads while his sim is getting new
cylinders.

He must have gotten his monitor onto the step :-)

george wrote:

He must have gotten his monitor onto the step :-)

George, you really made me smile with that comment :-) Extremely
clever, inside pilot joke... and not mean.

Thanks!
Kev

In article ,
says...
This morning I'm flying my sim Baron 58 towards KVYS, and I notice
that my airspeed is about 217 kts, much higher than usual. I'm level
at 5000 feet MSL, altimeter is 3038, clear weather, throttles full,
mixture set for peak EGT roughly, props set to 2520 RPM, about 150 RPM
below redline. The temperature outside is -1° C.

The mystery for me is that 217 kts (slightly in the yellow arc) is
unusually fast. I'm not sure what I'm doing different. Usually I'm
just below the yellow arc in cruise at this range of altitudes.

So throttle, mixture, prop, and altitude can surely affect IAS in
level flight, but what else? How much does the gradual burning of
fuel make a difference? Would it boost my speed by 20 kts or more as
it burns off? I started out with almost a full load of fuel, and now
about half of it is gone.

I'm just trying to figure out what factors I may be overlooking.

Temperature *and* pressure (ie what's the QNH?).

Other obvious factors, loading (including fuel).

--
Duncan