Chris Cosman wrote:

My question is, since diesel fuel is heavier than gas is the HP/pound

of fuel

still about the same?

The HP/lb depends not only on the fuel, but also on the engine.  Recall

thast

engine's can be rated by the BSFC.  That's HP / lb / hour.

If you want to talk about energy available per pound, that would be

Btu/lb.

Gasoline and diesel are roughly equivalent on a Btu/lb basis (both in

the range

of 18,000-19,000 Btu/lb), but since diesel is denser, diesel has more

Btu/gal

(128,400) than gasoline (115,000).  See:

http://afdc.nrel.gov/pdfs/fueltable.pdf

It's also easy to see that adding oxygenates (ethanol, methanol, or

MTBE) lowers

the energy per gallon of gasoline.  Less energy per gallon equals more

gallons

per hour for the same HP in a given engine.  Yet another reason to avoid

alcohol

when using mogas to fly.

Now if we could just find a safe way to carry pure hydrogen...  :-)

Russell Kent

Safety is not the issue --- it is just so damn light - the BTUs per gallon
of even cryogenic
liquid is very little - less than 1/8th that of gasoline and add the weight
of the vacuum
jacketed dewer that can only keep it from evaporating  a bit slower than you
can burn it,
and it becomes a lose lose proposition. Hydrogen is great for spacecraft
where the
low molecular weight gives you lots of miles per gallon, but it is crummy
for cars
or airplanes. Vance

 
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