Originally Posted by
detpilot
I'm skeptical of this "magical" car of yours, but in any event- at those speeds, gearing has little impact on your fuel burn. If your statement about your car's performance was true, better gearing doing the rpm down to 3000 rpm would have a very minor effect on mileage, if the engine could even maintain the load at that rpm. People overestimate the effect of gearing, especially at high speeds in automobiles.
Gearing has EVERYTHING to do with fuel burn in a car, and has an almost exponential effect on your fuel burn as speed increases.
When I raised my final drive ratio by .15 (a noticeable, but small change), fuel mileage at higher speeds dropped by about 7 mpg. Drag does play a significant factor, but gearing in a vehicle is much more of a factor than you account for.
I'm almost curious to see what would happen if I dropped my final drive down by .45, I might even have the proper unit in my garage, but it would rob my acceleration by a noticeable factor.
Comparing a rv10 to a certified airplane is not fair, I guarantee the rv stall speed is greater than the 61 knots that the faa requires for certificated single engine pistons. That diesel rv is impressive, but unless regulations are relaxed, no certified airplanes will be able to compete on a speed per horsepower basis.
RV10 published stall speed is 57 mph statute, which equates to under 50mph nautical. You could certify the RV10 yourself if you wanted, you'd just have to shell out the clams to buy a few kits and build them all the same way and then get a type certificate from the FAA.
As for airplanes vs cars, theres no doubt you can make cars more efficient. Several of the newer diesels are capable of more than 100mpg if driven properly, however airplanes can be made comparably efficient. Klaus Savier did a 1985 sm transcon in his two seater VariEze, using only 25.8 gallons, that's about 77mpg, he's been known to hit almost 100 mpg in competitions as well.