Quote:
Originally Posted by RobertSmalls
Jack the car up, off its rear wheels, to find out what the suspension looks like near maximum deflection. Options include a flexible panel spanning the axle, or an underbody panel mounted to the axle.
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I ran this experiment slightly differently, but the bottom line is; there is plenty of clearance. I jacked up one side until the tire just cleared, the theory being that this represents the limit of weight transfer, and took the clearance measurement. There is 1.5-2 inches of clearance remaining, so a straight forward large panel covering the entire rear works.
[QUOTE]As to whether the performance improvement would be measurable, well, how good is your measuring technique?
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I've been doing some "testing of testing," but I remain convienced that small incremental improvements will be below the measurement noise on a FE twichy car like the Insight. An approach which tests several "known" improvements at one time has its own shortcomings, but the combined improvements will probably be measurable.
[QUOTE]On the subject of diffusers, MetroMPG posted a promo video a while back that accompanied the release of the Insight. It was not written for a technical audience, but the voiceover guy mentioned that "the coefficient of drag was reduced by keeping frontal area to a minimum"*, and the (7° by my measurement) slope behind the rear axle "reduces turbulence underneath the car".[/UNQUOTE]
I pretty much agree that using a rear belly pan to smooth up the rear and extend the effective area is going to make the diffuser area more effective, particularly if you install a boattail. The lower spring perches and the lower shock mounts will protrude, but even these could be covered by small bulges.