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Old 02-01-2014, 03:29 PM   #9 (permalink)
aerohead
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GM Impact/EV1 LSR

Goro Tamai had some numbers for GM's land speed record car in an endnote on page 19.
In 1999 GM reported Cd 0.197 for Impact/EV1.
For the speed record they:
*deleted wipers
*covered over the cowl area
*deleted the side-view mirrors
*created fairings at the lower front tire leading edge
*installed flat aluminum wheel disks
*added the 16-inch "Yellow Ferret" boat tail
*taped over body gaps
*lowered the car 40 mm (1.57")
*installed Michelin speed-rated tires
*the nose fascia was devoid of any openings
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Goro Tamai reported that GM's team got the Cd to 0.14 (if frontal area was considered a constant).That could mean Cd 0.149 if considering 'points.'
Since the frontal area was impacted by the mirror delete and lowering,the Cd was probably a bit higher.
By itself,the tail pushed top speed from 178 mph,to 183.From Hucho's drag/speed relationship this would roughly equate to a 8.4% drag reduction.
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