Posted by Polar Pilot on September 27, 2000 at 16:56:31:
In Reply to: Cool Air - Run Better? posted by Jabawaki on September 27, 2000 at 15:02:39:
A bit of physics - cool air is "thicker" - technically denser. Because of the higher density - it carries more atomized gasoline (the carb is essentially an glorified perfume atmoizer) your engine will produce more power and run smoother.
In modern carburated/fuel injected engines we are rarely aware of how much change air temperature can make to engine power and smoothness.
On most single engined (piston) engined airplanes there is a control to help deal with ice forming in the carb - when carb heat is selected, which is preheated air drawn from around the muffler, the rpm on a 150 hp 320 cubic inch plane engine will drop by up to 150 rpm - from 2250 to 2100 rpm. Close the carb heat and the rpm's immediately pick up again. In the case of airplanes cooler temperature also impact on the lift of the wings - flying in the arctic at -10 gives us far greater performance from the airplanes than at +20.
So your observations are 100% correct - you would have both a smoother and more powerful engine with lower temperatures.
As the temps lower, we come closer to our magic 31 ponies which is the theoretical hp our steeds will produce under standard conditions.
Keep the rubber side down
Polar Pilot