Quote:
Originally Posted by Tesla
Did some more measurements, bit rough, just for a guesstimate.
Current rear dimensions and area in inches - 72 wide base, 48 wide top x 60 high, by my calculations = 3600"sq
at about 14 degrees on top at 36" extension is 9" drop in height, 14 degrees at each side at about 24" come in 6" each.
New rear area would be 60 wide base, 36wide top x 51 high, which comes to 2448"sq.
As a percentage that is 32%, so going by the general rules I could expect 16% FE improvement, providing it is done right.
Particularly if I skirt the rear wheels and taper in from the skirts in the lower section with other trimmings I could hope to crack the 15% mark.
Most of my travel is highway & higher speeds generally.
Not just a pipe dream I hope, will go and do some Payback figures based on a 15% improvement.
Edit 1 : Assumption error, just remembered read somewhere around 30% drag is from the back & overall aerodynamic drag is 65% of fuel consumption at higher speeds, this would mean a 30% reduction in the rear is only 6% improvement in FE.
Edit 2 : Found calculation error in surface area, corrected above, doesn't change much.
Hope there is better opinions out there, please comment on the numbers, what's the likely improvement in fuel economy if rear drag is reduced 30%?
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On the CRX,a 12" tail and rest of 'kit' got me a 16.5% increase in mpg.
On the VW bus,an 18" tail and other mods got me up to 29.6% mpg.
24" of boat tail is a serious mod
Walter Lay was getting Cd 0.20-21 with 35% of (Template) tail.I think you'll be amazed.