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Oltmannd: [quote]QUOTE: - AC in a 250 mpg car would drop your milage by 75 mpg, not 20 or 30. Just turning the headlights on would drop gas mileage by 25 mpg. Do the math![/quote] Typical wattage of headlights is about 50-70 watts. That is 100-140 watts. A gallon of fuel will light them for 100-140 hours. At 30 mph average you will do 3000 miles. So the lights are 3000-4200 mpg. In 3000 miles our 250mpg car will burn 12 gallons. 13 with lights. 3000/13 = 230 mpg In 4200 miles our 250mpg car will burn 16,8 gallons 4200/17,8 = 235 mpg This is assuming running with headlights on non stop. Usually your lights will be on what - 20% of time? 10%? That will cost 5 or so mpg (20%). [quote]QUOTE: -Formula 1 cars do not meet Fed requirements for safety. They are "safer" than they were 30 years ago, but they are certainly not what anyone would call "safe". How you can even say they are the "safest" is beyond me! [/quote] Think about it -on each race several of those cars crash at 100+ mph - and yet not many casualities are there... [quote]QUOTE: Yeah, I know you could make cars a lot lighter using composites w/o sacrificing strength, but even if you dropped the weight from 2500# to 500# you still have some serious aerodynamic issues and I don't think you can drop the Cd low enough and still package the interior into one an aging baby boomer or soccer mom would accept.[/quote] Aero issues can be resolved - maybe not as drastically as in that 12500 mpg car, but surely they can. [quote]QUOTE: 250 mpg is just not possible for a family sedan! 75, maybe. 250, forget it![/quote] Say that when fuel will be at 20$ @ gallon [quote]QUOTE: Besides, for a car traveling 20,000 mi/yr with fuel at $5, going from 25 to 75 mpg will save ~$1700/yr but going from 75 to 250 will only save ~$700/yr more.[/quote] 20000 miles @ 10 mpg = $ 10000 20000 miles @ 25 mpg = $ 4000 20000 miles @ 75 mpg = $ 1334 20000 miles @ 250 mpg = $ 400 Obviously - we save most by going from 10 mpg, to 25 mpg. So - the rest is irrelevant... Besides - afair 70mpg car is already avalible - it's called Volkswagen Lupo 3.0 As for transmission losses: Typical gearset is about 97-95% efficent. Bearings are about 99%. Clutch - depending on the age is about 95-85% efficient. A shaft is about 98%-95% (the longer the less efficent - altho the diameter also counts the bigger diameter - less twisting thus higher efficency) typical drivetrain is: cylinders -> shaft (0,98) -> clutch (0,95) -> shaft(0.98) -> gearbox (0.93~0,95) -> shaft(0.98) -> differential(0.95) -> clutch(cardan)(0,97) -> shaft(0,98) -> clutch(cardan)(0.97) -> shaft(0,98) -> wheel = total efficency: 0,77. That is exocluding suspension (it eats some power) and bearings and assumes mint, well lubricated conditions. 0,7 for a new car and 0,6-0,65 for old is about right. Modelcar: there are ways to move a human at 12500 mpg. We are discussing how much of that can translate to a sensible personal transport - I shoot at 200-250 mpg
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