I found some info though not directly related to the question it is interesting. P.S all stolen info. Not mine.
The reason Nitromethane is such a good fuel is basically that it requires less oxygen to fully burn (oxidate) each molecule. For instance:
100 octane gasoline is mostly C8H18
2(C8H18)+25(O2) => 18(H20) + 16(CO2)
A ratio of 25/2 = 12.5 Oxygen molecules per fuel molecule
Nitromethane is CH3NO2
4(CH3NO2) + 7(O2) => 6(H2O) + 4(CO2) + 4(NO2)
A ratio of 7/4 = 1.75
So nitro requires over seven times less oxygen per molecule than does gasoline. Unfortunately, it's not quite as dense as gas, but after figuring the energy densities in, we still find that nitromethane nets you about 2.5 greater combustion power per pound of oxygen.
Methanol (CH3OH) is even better!
2(CH3OH) + 3(O2) => 4(H2O) + 2(CO2)
A ratio of 3/2 = 1.5
Figuring in the energy density, it's almost 3 times the combustion power of gasoline! But it's more dangerous to handle than nitromethane, and it's far more corrosive to the engine parts.
SO Nitromethane can produce 130% more energy than gasoline per kilogram of air. And contrary to my earlier post - methanol is a measly 11% better than 100 octane gasoline!
Side note:
Diesel and gasoline are witches brew - I couldn't even pretend to guess what's really in them anymore. Standard gasoline is generally a mix of heptane, octane, and nonane. Standard diesel fuel is classically tetradecane (C14H30) - but diesel is very unrefined. In general, for aliphatic carbon chains, as the chain gets longer, RON increases, the energy density increases, the "stoichiometric factor" decreases, and the heat of vaporization increases.
OK - here's the actual numbers (with units! 
):
Oxygen (O2) is about 23% of the atmosphere by mass (21% by volume)
So, one kg of air contains about 0.23 kg of O2,
and 0.23kg / (32 g/mole) = 7.2 moles of O2 per kg of air
Fitting our balanced equation,
2(CH3OH) + 3(O2) => 4(H2O) + 2(CO2)
we can combust 2 moles of CH3OH for every 3 moles of O2. So to fully use up one kg of air, we need:
7.2 moles O2 * 2 moles CH3OH / 3 moles O2 = 4.8 moles CH3OH
and thus
4.8 moles CH3OH * 32 g/mole = 153 g of CH3OH
Therefore our mass stoichiometric ratio is:
1,000 g air / 153 g CH3OH = 6.51 mass air / mass CH3OH
Conversely:
153g CH3OH / 1,000 g air = 0.153 mass CH3OH / mass air
Ta da!
If you want to use my earlier "stoichiometric factor" to get the mass ratio (with atmospheric free Oxygen) just multiply it by the factor by (23% / 32 ) = 0.00719 to get mass CH3OH / mass air
So, here are the new numbers, in their correct, happy form:
Stoichiometric mass ratio (mass air / mass fuel):
1) nitromethane ( 1.72 )
2) methanol ( 6.51 )
3) gasoline (iso-octane) ( 15.4 )
4) diesel** (iso-tetradecane) ( 20.3 )
Fuel energy per mass air:
1) nitromethane ( (12,000 kJ/kg fuel) / (1.72 air/fuel) = 6978 kJ/kg air )
2) methanol ( (22,725 kJ/kg fuel) / (6.51 air/fuel) = 3490 kJ/kg air )
3) gasoline ( (47,895 kJ/kg fuel) / (15.4 air/fuel) = 3110 kJ/kg air )
4) diesel** ( (56,324 kJ/kg fuel / (20.3 air/fuel) = 2775 kJ/kg air )
For those who don't know, a kJ is a kilo-joule, a measure of energy equal to 2398 calories or 0.278 Watt-hour.
Fortunately for my ego, the proportionalities are close to what I reported before. (I attribute any differences to round-off error - I haven't carried many decimal places.) Nitromethane can produce 125% more energy per kg of air than 100 octane gasoline can. And methanol is only 11% better than the gas.
Make sense to everyone now?
**Note: I calculate diesel using only tetradecane (molecular weight of 198) as follows:
(C14H30) + 29(O2) => 30(H2O) + 14(CO2)
So the molecular stoich ratio is 29/1.
The mass stoich is (deep breath!):
(32 g/mol O2 / 23% (g O2 / g air)) * (29 mol O2 / 1 mol C14H30) / (198 g/mol C14H30) = 20.3 mass air / mass C14H30
**Note part II: Actual diesel fuel is a huge mix of chemicals, from C3H8 to C25H52 and beyond - it's exact stoich ratio will depend heavily on the mixture - I would assume that to get to the 13.9 mass stoich ratio that texan reports means that diesel fuel has a fair component of smaller than C14H30 molecules as well as aromatic compounds that do not break during combustion.
