Posted by Eric on May 5, 2006, 9:35 pm
I was wondering what the theoretical limit was on gas mileage
Someone somewhere must have figured that out that.
The ingredients would be something like:
1. some kind of standardized vehicle shape and weight
2. a specified driving profile (ie speed) over a fixed course
3. a specific gasoline formulation (unleaded 89 octane)
4. determine the amount of energy in a gallon of the above fuel
and compute energy required to complete the course, thus
giving you computed mpg at absolutely 100% efficiency
The results might be quite enlightening, especially when the same
calculations are done for a variety of fuels (ie diesel, hydrogen etc),
graphing against speed, car body shape, weight etc
It might also debunk a lot of those wacky claims by hucksters trying to
sell you various pills/additives/carburettors etc to get "better mileage"
AND, here's a nifty benefit, it would help people to compare various fuels
so you could make a somewhat better informed decision about alternatives.
Posted by rebel on May 5, 2006, 9:57 pm
I have a French vehicle an Axiam it is a bit crap and expensive for what it
is it's saving fact is it returns 80 mile per gallon. good for rural work
Posted by Harry Chickpea on May 6, 2006, 12:01 am
Do a web search and you'll eventually come across the "racers" that go
for this. IIRC, 600 to 800 mpg is the norm, but it probably is much
higher now. Ultralightweight, super-hard tires, tiny engine, slow
speeds and a lot of coasting. No provision for even much venting,
much less air conditioning.
Posted by BobG on May 6, 2006, 1:56 am
Rolling friction and drag is what uses the gas. Sports cars have drag
coefficients like .25. Trucks are like .9. The formula for drag is
.5*rho*V^2*S*Cd. rho is air density... 1.2 kg/m^3 about. S is the
frontal area in m^2. It takes about 15Hp to push thru the air at 40mph,
but it starts going up fast. A 100mpg car would have to be real light
(small rolling friction) and real slippery. Like maybe 1500lbs, 20HP,
and cruising at 45 or 50. And hi pressure tires.
Posted by danny burstein on May 6, 2006, 2:46 am
The Honda Insight - gasoline powered, hybrid - has a bunch
of crazed owners.... The _regular_ and real mpg on the
manual is typicaaly 70 or so highway. (My personal range
is normally about 55-60 on the highway with auto transmission).
Every so ofen one of the " hyper-milers " reports doing over 100 mpg.
(I've gotten as high as 75.4 on a 50 or so mile stretch. There
was a steady 30 + mile wind helping...)
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