Hybrid Car – More Fun with Less Gas

Vehicle Gas Consumption - Accurate? - Page 5

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Posted by Elmo P. Shagnasty on May 11, 2012, 9:25 pm

Pray tell.

You refuse to dispute this in detail...why?

Posted by News on May 11, 2012, 9:57 pm
On 5/11/2012 5:25 PM, Elmo P. Shagnasty wrote:

You already answered the question, but fail to realize it:

"Lower energy content fuel will deliver fewer miles per volume,
regardless of whether you're measuring it at the pump or the engine
computer is measuring it at the injector."

Posted by Elmo P. Shagnasty on May 12, 2012, 1:52 am

That's right.  And that calculated number will REFLECT the lower
energy--but the calculation itself, and the final number, does not
depend on knowing the energy content of the fuel.

I'll make it simple:  how is a straight "I drove X miles on Y gallons of
fuel, which calculates to Z miles per gallon on that tankful"
calculation *wrong* because it is missing the energy content of the fuel?

It's not wrong.  It's a straightforward calculation.  And Toyota's
engine computer is doing the exact same calculation, only at the
injector pulse level.

You can't tell the world how such a straight calculation requires
knowledge of the energy content of the gas, because it doesn't.

If I were able to put in a "price per gallon" figure inside the Toyota
computer, it would immediately know how much an injector pulses
costs--and it would be able to total up the number of injector pulses
per mile and tell me how much I paid to drive that mile.

Lower energy content fuels will require more fuel delivered to make the
car go the same distance.  We all know that.  But it's not important to
the raw MPG calculation.  The raw MPG calculation will, instead, show
that fact.

Posted by News on May 12, 2012, 3:49 am
 On 5/11/2012 9:52 PM, Elmo P. Shagnasty wrote:

The inaccuracy -- which was my original comment -- is in the failure to
compensate for fuel chemistry/energy content.

Posted by Elmo P. Shagnasty on May 12, 2012, 1:25 pm

The "inaccuracy" we're discussing is the difference between the number
on the screen and the number people get by manually calculating the
number of miles they drove this tank against the number of gallons of
fuel they put in to fill the tank.

All sorts of things can happen to cause that discrepancy, NONE of which
have anything to do with the fuel energy content.

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