Fun facts, kinda OT, for the bored Options

[lapuwali]

1 US gallon of gasoline contains 104,000 BTUs of energy.
1hp = 2,540 BTU/hour of energy consumption.

A typical car requires about 9hp to cruise at 60mph, given aero loads and rolling resistance from tires.

So, if engines were 100% efficient at extracting energy from gasoline, you'd get 273 mpg at 60mph in a typical car. Since most cars actually get less than 30mpg, most engines are extracting roughly 10% of the energy in the gas and applying those to actually propelling the car. Most of the energy is being thrown out as waste heat directly out of the exhaust, or in heating up the coolant, the engine itself, the gearbox, and the tires.

btw, hydrogen has 180,000 BTU/US gal, so if a liquid H2 fuelled engine were produced that only had the same efficiency as a 27mpg gasoline engine, you'll see 45mpg typically.

Pure ethanol has only 70,000 BTU/US gal, for only 18mpg. E85 would bring this up to 20mpg. Britt noted E85 where he lived was $2.10/gal v. $2.58/gal for gasoline, meaning E85 costs 81% as much, but only takes you 74% as far...

Now, as for the efficiency of a Mr. Fusion powered car...

[lapuwali]

QUOTE (SGB @ Aug 23 2005, 07:12 PM)

uh..... (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif) it's like (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif) oh wait. I already did this... Really James, all that is damn fascinating. I'm assuming there is some basis for the numbers you come up with. Shows why it is easier for the oil industry to cavort with people who don't actually like 'em instead of developing other sources, I guess. So we gotta develop a better way to capture turbine energy and convert to appropriate rotational forces. Sounds like it could be pretty inefficient and still be an improvement....

The numbers I quoted in the first post were primarily from a Wikipedia article (BTUs/gallon), and from coast-down figures Car & Driver used to put in their road tests (9hp for an Accord-class car). btw, motorcycles are much worse, at 12hp for 60mph, due to terrible aerodynamics (from Cycle magazine). The rest is just straight, simple math. I'd read years ago that an IC engine was about 30% efficient at the crank, at best. Given known figures for gearbox and final drive losses, 8-15% sounds about right.

The oil figures I got off the web, just googling. They could be very wrong, but sound about right.
The prices/barrel or gallon are, of course, right out of the news.

The gas turbine figures are also out of Wikipedia, and the problems as a direct drive powerplant are from a fascinating story relating to the history of BRM (British Racing Motors), which built a car around a gas turbine engine made by Rover in the mid-1960s, driven at Le Mans by Graham Hill. This story has been related by Doug Nye, in his history of BRM.