Quote:
Originally Posted by Frank Lee
Since this second point refers to ride height and not how far out the sides wheels are, it seems to contradict the prior point, since a lower ride height causes the wheel to fill up the well more.  |
Frank,you're correct.
The message I took away was that you'd minimize the wheelhouse as best you can,with an eye on active suspension,bringing the tire up into the body for it's lowest drag configuration on the highway when it counts the most.
Cogotti's (sp?) test model showed about a 0.078 drag increase when his big honkin' wheel wells and wheels were added to his drop car.
Buchheim,when he did the VW 'Flow' body (long-tail),adding the minimized wells and wheels pushed the Cd from 0.0915,to 0.14,only a 0.0485 drag increase.
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The report on the VW Jetta hybrid land speed record car said that the mirror delete,wiper delete,lowering,and narrow tires did not affect the Cd,only a CdA reduction from frontal area.
Tamai reports that The GM Impact land speed record car,with same mods as the Jetta,except for a covered cowl and 0.5-meter boat tail,went from Cd 0.19,to Cd 0.14 if you calculate at a constant frontal area.(not really the case).They don't break out the contribution from 'hiding' the tires a bit.Wish they did.
Finally,early in Tamai's book,he mentions that the wheel fairings,even though they add frontal area and wetted area,do produce an overall drag reduction.So it looks like the wheels/wells are something worth investing time with.Hope he expands on all this later.Hucho really doesn't get into it.