Posted by News on May 11, 2012, 12:37 pm
On 5/11/2012 8:18 AM, Elmo P. Shagnasty wrote:
>> How can they get it that consistently wrong?
>>
>> The volume of fuel injected is measured, energy content not-with-standing.
> So far so good.
>> For example, the same volumes of 100% 87 octane gas, 87 octane E10, or 89
>> octane gas will yield different mileage figures.
> Yes...
>> The manual specifies 87
>> octane so I suppose it's calibrated to the average energy derived from 87
>> octane, 100% gasoline.
> It's not "calibrated" to anything like that.
>> Where I live E10 is mandated by law so I would
>> expect the mileage displayed by my Prius to be higher than my actual
>> mileage.
> WTF?
> An injector pulses X amount of gas. X times the number of injector
> pulses is the total gasoline used. Calculate that against the miles
> driven in that number of injector pulses.
> This is just a fancy engine computer calculated version of the very same
> thing people do when they calculate their mileage at the pump based on
> how much gas they put in the tank and how many miles they drove since
> the last fillup.
> The energy content of the fuel is *reflected* in the final calculation,
> but it is not *part* of the calculation. It used THIS much gas, and
> drove THAT many miles--period. 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.
Hence the need for fuel chemistry compensation.
Posted by Elmo P. Shagnasty on May 11, 2012, 3:20 pm
> > The energy content of the fuel is *reflected* in the final calculation,
> > but it is not *part* of the calculation. It used THIS much gas, and
> > drove THAT many miles--period. 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.
>
>
> Hence the need for fuel chemistry compensation.
not at all.
All we're looking at is the miles per gallon calculation.
Lower energy fuel will deliver fewer miles per gallon. Calculate it any
way you like, at the pump or at the injector, it's all the same
calculation. Energy per volume unit of fuel is irrelevant to the
calculation of how many miles will that volume of fuel take you.
I keep reading on Jalopnik all the bias against hybrids and for diesels,
but all they can spew is "miles per gallon". That in and of itself is
meaningless when diesel fuel is always more expensive, sometimes
significantly so, than gasoline.
Me, let me plug into the computer the unit price I just paid for that
fuel--now the computer can tell me the REAL fact I want, which is my
fuel price per mile.
And nowhere in this is any need to know or compensate for the fuel
chemistry.
Posted by News on May 11, 2012, 3:38 pm
On 5/11/2012 11:20 AM, Elmo P. Shagnasty wrote:
> Lower energy fuel will deliver fewer miles per gallon
> tell me the REAL fact I want, which is my
> fuel price per mile.
> And nowhere in this is any need to know or compensate for the fuel
> chemistry.
Wrong.
Posted by Elmo P. Shagnasty on May 11, 2012, 8:05 pm
> On 5/11/2012 11:20 AM, Elmo P. Shagnasty wrote:
>
> > Lower energy fuel will deliver fewer miles per gallon
>
> > tell me the REAL fact I want, which is my
> > fuel price per mile.
> >
> > And nowhere in this is any need to know or compensate for the fuel
> > chemistry.
>
> Wrong.
yeah, keep telling yourself that.
In the meantime, I will continue to buy specific volumes of fuel at
specific prices and have that fuel propel me a specific number of miles
down the road, and will be able to calculate (a) my number of miles per
gallon, and (b) my fuel price per mile--
--all without knowing OR CARING about the fuel chemistry.
Again, the numbers I calculate will *reflect* the fuel chemistry, but no
one needs to know the fuel chemistry in order to calculate those numbers.
Your insistence on calling that "wrong" tells me you're not paying
attention.
Posted by News on May 11, 2012, 8:20 pm
On 5/11/2012 4:05 PM, Elmo P. Shagnasty wrote:
>> On 5/11/2012 11:20 AM, Elmo P. Shagnasty wrote:
>>
>>> Lower energy fuel will deliver fewer miles per gallon
>>
>>> tell me the REAL fact I want, which is my
>>> fuel price per mile.
>>>
>>> And nowhere in this is any need to know or compensate for the fuel
>>> chemistry.
>>
>> Wrong.
> yeah, keep telling yourself that.
> In the meantime, I will continue to buy specific volumes of fuel at
> specific prices and have that fuel propel me a specific number of miles
> down the road, and will be able to calculate (a) my number of miles per
> gallon, and (b) my fuel price per mile--
> --all without knowing OR CARING about the fuel chemistry.
> Again, the numbers I calculate will *reflect* the fuel chemistry, but no
> one needs to know the fuel chemistry in order to calculate those numbers.
> Your insistence on calling that "wrong" tells me you're not paying
> attention.
Read your own drivel and you'll conclude you've impeached yourself.
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>>
>> The volume of fuel injected is measured, energy content not-with-standing.
> So far so good.
>> For example, the same volumes of 100% 87 octane gas, 87 octane E10, or 89
>> octane gas will yield different mileage figures.
> Yes...
>> The manual specifies 87
>> octane so I suppose it's calibrated to the average energy derived from 87
>> octane, 100% gasoline.
> It's not "calibrated" to anything like that.
>> Where I live E10 is mandated by law so I would
>> expect the mileage displayed by my Prius to be higher than my actual
>> mileage.
> WTF?
> An injector pulses X amount of gas. X times the number of injector
> pulses is the total gasoline used. Calculate that against the miles
> driven in that number of injector pulses.
> This is just a fancy engine computer calculated version of the very same
> thing people do when they calculate their mileage at the pump based on
> how much gas they put in the tank and how many miles they drove since
> the last fillup.
> The energy content of the fuel is *reflected* in the final calculation,
> but it is not *part* of the calculation. It used THIS much gas, and
> drove THAT many miles--period. 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.