Quote:
Originally Posted by clivem2
Hey, I'm no expert on this and you're doing a great job! What I believe is the case is that if you have a 3 series and X3 with a Cd of say 0.33 then the X3 will have the greater wind resistance due to it's frontal area. Yes CdA is simply the normal shorthand for Cd * A.
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Thanks, Clive.
I have almost completed the graph for all models, but given the higher HP max for the upper echelon power types, I will need to zoom the scale at different speed intervals (low, medium, and high) to show the differences more clearly. The next question, depending upon how compulsive one wants to be, would be to figure out the fuel usage of one HP - for if that variable is known, one could almost construct a usage chart for mpg/mph for each type. That seems way beyond the scope of this inaccurate model, but would still be a reasonable concept if so inclined. I have to think that what seems like even small differences, such as 20 HP, at constant speed probably does make a big difference in the mpg differences seen between types.
Also, I will produce a(n) 'X3-only' graph showing how changes in our X3's Cd, 'A', weight, and combinations thereof can lead to prominent changes in the 'HP vs Speed' curves.
What I am surprised about, is that the 'M' series are not necessarily groomed to be 'clean'. It seems their Cds are higher than some of the base models, which now is making more sense, for at the speeds some of these models are capable of reaching (if not limited), they would probably begin to have too much lift (thereby reducing friction and power/performance ability, and become unsafe at top-end speed, hence the need for modifications to keep them earthbound, which by definition, must induce a degree of drag).
Good stuff, and must make coming in to work each day as a BMW designer a joy.