Quote:
Originally Posted by Cycle
Quote:
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Originally Posted by IamIan
BTU/Mile already does .. it includes both the amount of fuel and the fuel's energy density ... thus making it superior to the less information from just using gallons , liters, etc.
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How so? What volume of fuel that comprises a single BTU will drive the car for a specific distance? |
Explaining:
The specific volume (or weight) of fuel to get 1 BTU will vary with the energy density of the specific fuel.
Propane has a different energy density than gasoline .. different than Diesel .. different than hydrogen .. etc... But 1 BTU = 1 BTU.
The volume of the fuel will change with different conditions (temperature, pressure, etc) ... but the BTU contained in it does not change .. 1 BTU = 1 BTU.
Energy (BTU) is the capacity to do work (volume is not) ... if you want to know the capacity to do work .. you want to know the amount of energy (BTU).
Quote:
Originally Posted by Cycle
Especially considering that different engines will have different efficiencies, some throwing away more of those BTUs than other engines.
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Exactly.
What % of that previously sited 5% was due to engine differences alone (ie the portion that did not come from the propane itself.)
Quote:
Originally Posted by Cycle
If we bought fuel by the BTU, his point would have more merit... but we buy our fuel by volume.
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Energy is the capacity to do work (ie move the car) .. thus units of energy (BTU) is the best units to use to determine one's ability to do work (ie more the car).
Someone could sell it to me by the BTU .. by the kg .. by the barrel .. for chickens .. for milk .. etc .. etc.
How someone chooses to sell it to me does not effect it's capacity to do work .. thus back to the units of energy (BTU)
Quote:
Originally Posted by Cycle
So it all comes back to volume... MPG.
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Disagree .. see above.
Weather you personally like the BTU/mile method or not .. that is the method that was sited to you in the comments made above.
Quote:
Originally Posted by Cycle
As for "it's too small a difference"...
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No... It seems you misunderstood.
I'll try again.
How do you differentiate the efficiency BTU/mile effects of:
#1> The Fuel
from
#2> The modifications you made to the engine itself.
and
#3> What is the expected variation (noise) one's result must surpass to indicate a significant signal ?
For example of 1+2:
I can run my ICE with gasoline from gas station A .. get say 50MPG .. Than I modify my ICE to run in Lean Burn .. I buy gasoline from station B .. say I got 60MPG ... the fuel alone is not the only reason for the change in MPG .. The changes made to the ICE itself contribute.
Example of 3:
Same as previous example .. but say I made no modifications to the ICE at all .. is that same 20% variation in MPG from one trip to the next a large enough difference to surpass the 'noise' one would expect from different trips .. and be able to reasonable assume the difference was caused by different gasoline from Station A vs Station B.
Quote:
Originally Posted by Cycle
what about "the amount of fuel per unit volume of air for propane is approximately twice that of gasoline just to reach that fuel's flammability range" and "propane has only ~73% of the energy content of gasoline on a per volume basis" yet "propane still exhibits a higher fuel efficiency than gasoline" don't you understand?
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As explained previously .. on an energy basis (BTU/mile) .. the difference is soo small it can easily almost entirely be just from the modifications made to the ICE that produced it.