I scratched out some numbers:
*I took the 64" width and resolved it into a semicircle of 32" radius for the greenhouse.
*From the beltline down to the belly,just a 64" by 18" rectangle.
*Then using 145mm tires,at 8" exposure X 3 for the three wheels
*This gets me a projected frontal area of 20.121 sq-ft.
*At Cd 0.15 we'd have a drag factor of CdA 3.018 sq-ft (0.28 sq-m)
*At 1,300-lb,with 170-lb driver,the test weight would be 1,470 lbs.
*With 9.0 bhp,and a powertrain mechanical efficiency of 94% we'd have 8.46 hp available for propulsion,which would also be its road load at top speed.
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Using Honda R&D Co.,Ltd's R-R power curve for a 1996 Accord I did some iterations to dial in the velocity at which 8.46 hp would be consumed.This is with a Coefficient of rolling friction of Cf= 0.0134 lbs drag/pound vehicle weight.
*I came up with 63 mph for the top speed.
*With an enthalpy efficiency of 42% and 129,900 Btu/gallon diesel,we have 54,558 Btu's per gallon of useable energy.
*At 2544.433 Btu/horsepower-hour it gives 0.4197 gallons/hour= 150 mpg at 63 mph.
If I use a BSFC of 0.38 lbs/bhp-hr,at 9 bhp I get 3.42-lbs,or 0.4858 gallons/hour,for 129.6 mpg at 63 mph.
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A Lilliputian turbocharger would be handy for hills,but on the flat,the tadpole won't have much competition for mpg.
