Hybrid Car – More Fun with Less Gas

Vehicle Gas Consumption - Accurate? - Page 3

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Posted by News on May 8, 2012, 8:05 pm
 
On 5/5/2012 10:47 AM, PriusGeek wrote:

personality that I am, I have recorded for each tank the fill-up amount,
displayed MPG, outside temperature, cost and calculated the actual MPG.
Generally speaking, the Prius displays were all significantly optimistic in the
MPG department. Overall, on 25 fills so far on my 2011, actual MPG averages 6.2%
less than the MPG on the display.



How can they get it that consistently wrong?

Posted by Al Falfa on May 9, 2012, 5:32 am
 
"News"  wrote in message

On 5/5/2012 10:47 AM, PriusGeek wrote:

How can they get it that consistently wrong?

The volume of fuel injected is measured, energy content not-with-standing.
For example, the same volumes of 100% 87 octane gas, 87 octane E10, or 89
octane gas will yield different mileage figures.  The manual specifies 87
octane so I suppose it's calibrated to the average energy derived from 87
octane, 100% gasoline.  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.




Posted by News on May 9, 2012, 10:56 am
 On 5/9/2012 1:32 AM, Al Falfa wrote:

Fuel chemistry is easily measured and compensated-for, but not in this
case, apparently.

Posted by Al Falfa on May 10, 2012, 4:14 am
 
On 5/9/2012 1:32 AM, Al Falfa wrote:

Fuel chemistry is easily measured and compensated-for, but not in this
case, apparently.

Fuel chemistry in real time?  Oh c'mon now.  In the lab, perhaps, but not on
the road.



Posted by Elmo P. Shagnasty on May 11, 2012, 12:18 pm
 

So far so good.


 

It's not "calibrated" to anything like that.



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.

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