Tool for visualizing aero vs rolling resistance

[MetroMPG]

If you are so inclined...

well, i was *partially* inclined.

i updated the tool with the table data from wikipedia, so you can select from a range of pre-calculated rho (air density) values based on various temperatures. the table doesn't specify the other values used in the rho calculations, but i suspect they used "standard" values for pressure & water vapour content (humidity).

http://metrompg.com/tool-aero-rr.htm

while roaming around the web reading about this, i came across a very interesting page which actually does the rho calculation (javascript) from input values of air temp, absolute pressure, and humidity.

most interestingly, it then takes that info and calculates *relative engine HP*.

since our cars' engine hp figures are calculated by SAE rules at standardized atmospheric conditions, this tool shows the effects on HP of different atmospheric conditions (as they affect density of the intake charge).

For the SAE J1349 relative horsepower calculations, the standard reference conditions are: Air temp 77 deg F (25 deg C), 29.235 Inches- Hg (990 mb) actual pressure and 0% relative humidity.

http://wahiduddin.net/calc/calc_hp_abs.htm