Performance at low temperatures

[gilbertohasnofb]

This has been reported by @stuartbuchanan

I'm getting even better performance than I would expect at low
temperatures. Ground temperature was -4C, and I was able to get
1000ft per minute at 120kts up through 5000ft. I know that engine
performance is enhanced at low temperatures, but that's still very
good performance for a 160hp engine.

[gilbertohasnofb]

@dany93 do you think you could take a look at this at some point?

[dany93]

I've done tests.
Weight = close to 2400 lbs.
Air temperature = -4°C at sea level. Decreasing with altitude at -2° / 1000 ft, also changing dew point vs altitude.
Keeping very stable conditions is not easy, my more accurate way is measuring the altitude change in 1 or 2 mn (with the stopwatch).

At 120 KIAS airspeed, I find 750 to 850 ft/mn climb speed. But, at full thrust, the engine is at over range, close to 2800 RPM, 175 to 180 hp power.
I'm wondering if @stuartbuchanan would not have done his observations at default load (close to 1888 lbs).

The specified rate of climb vs air temperature can be found in the POH, e.g. C172P-6508k-poh.pdf p.5-14 (PDF 46/160).
For weight = 2400 lbs.
Climb speed: 76 to 73 KIAS.
As examples, at 0°C SL, it is 745 fpm at Sea level, 640 fpm at 2000 ft, 535 fpm at 4000 ft.

My tests in the POH conditions, -4°C at sea level:
Weight 2400 lbs,
Climb airspeed 70 - 80 KIAS.
Rate of climb 536 ft/mn between 1600 and 2700 ft altitude. Consistent with the POH data, rather not in excess.