Performance in the cold
Comments
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ShimanoBottomBracket wrote:Keezx wrote:Even when that's true, taking in more oxygen doed not mean that more oxygen reaches the muscles....limited by the cardiovascular system...
That sucks ass! The human body is pretty shetty in this regard. You'd think that more oxygen breathed due to denser air would mean more oxygen hitting the muscles. Yet we have to breath much faster during a workout. Could someone explain this mechanism in lay terms?
Yes this is an easy one to explain.....
Your O2 availability (oxyhaem dissociation curve) is already at maximum at sea level and not limited by air pressure under about 1000ft (rather by the oxygen carrying capacity of the haemoglobin concentration in blood itself....which is relatively fixed for nonEPO users). So given oxygen sat in blood and lungs is pretty much at its ceiling, it is the denser air of cold winter days has fairly big effect on aero drag as well as CDA (specifically on drag coefficient....but yes a little bit on the CDA*A* due to bulky clothes) times the inferior air pressure. further drag coefficient is amplified by most winter clothing (baggy, flappy, hairy, wooley etc) and lastly there is the massive effect of wind which is usually (as any cyclists knows) blowing in an unfavourable direction!
Hence winter Aerodrag is a combination of almost all variables being worse: Fa = 0.5 * Cd * A * ρ * (v + w)²
CD worse
A worse
P worse
W worse0 -
If it's any consolation I notice something similar with my car. It's a small, relatively light modern turbodiesel, and in the summer months the fuel economy can be astounding (the computer appears to be pretty accurate according to my occasional manual calcs)
But as soon as the temps start to dip in autumn / winter so does the average mpg. The denser air clearly has a big effect on drag. I have no idea if the engine management system is smart enough to factor in the higher O2 content of the air it takes in...0 -
Not my area of expertise but I wonder if - assuming mostly shorter journeys - the engine management software will run the mixture richer for longer as the engine takes longer to properly warm up.....keef66 wrote:If it's any consolation I notice something similar with my car. It's a small, relatively light modern turbodiesel, and in the summer months the fuel economy can be astounding (the computer appears to be pretty accurate according to my occasional manual calcs)
But as soon as the temps start to dip in autumn / winter so does the average mpg. The denser air clearly has a big effect on drag. I have no idea if the engine management system is smart enough to factor in the higher O2 content of the air it takes in...FFS! Harden up and grow a pair
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Svetty wrote:
Not my area of expertise but I wonder if - assuming mostly shorter journeys - the engine management software will run the mixture richer for longer as the engine takes longer to properly warm up.....keef66 wrote:If it's any consolation I notice something similar with my car. It's a small, relatively light modern turbodiesel, and in the summer months the fuel economy can be astounding (the computer appears to be pretty accurate according to my occasional manual calcs)
But as soon as the temps start to dip in autumn / winter so does the average mpg. The denser air clearly has a big effect on drag. I have no idea if the engine management system is smart enough to factor in the higher O2 content of the air it takes in...
more than likely, though I don't do many miles, I'm dangerously close to doing more by bike! when I do it tends to be for a good while, this is a old Volvo V70 tends to do low 30's lots of stop start traffic will make it eat fuel, but cold seems to make no difference, nor very high temps.0 -
Correct. Plus denser air will have an effect on drag especially at higher speeds.Svetty wrote:
Not my area of expertise but I wonder if - assuming mostly shorter journeys - the engine management software will run the mixture richer for longer as the engine takes longer to properly warm up.....keef66 wrote:If it's any consolation I notice something similar with my car. It's a small, relatively light modern turbodiesel, and in the summer months the fuel economy can be astounding (the computer appears to be pretty accurate according to my occasional manual calcs)
But as soon as the temps start to dip in autumn / winter so does the average mpg. The denser air clearly has a big effect on drag. I have no idea if the engine management system is smart enough to factor in the higher O2 content of the air it takes in...0
