Calibration of MPG shown on 2010 Prius

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Old 25 Oct 2012, 10:08 am   #1 (permalink)
VStarGuy
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Default Calibration of MPG shown on 2010 Prius

Can the MPG amount shown be calibrated on a 2010 Prius?

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Old 25 Oct 2012, 11:08 am   #2 (permalink)
DA
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Default Re: Calibration of MPG shown on 2010 Prius

responding to
http://www.motorsforum.com/prius/cal...ius-11510-.htm
, DA wrote:
> VStarGuy wrote:
>
> Can the MPG amount shown be calibrated on a 2010 Prius?
>


I don't believe calibration as such is even possible. My 2009 has a fuel
indicator that is often wrong and it's random. Calibrating a meter that misses
the mark by a random amount would make no sense. I always chucked it up to the
bladder that's in the tank but I don't know if that's what actually happens -
my 2006 second gen Prius I had before had the same tank design and the fuel
gauge was pretty accurate nevertheless.

I always go by the "miles since last fill-up" counter that's on the bottom of
the MPG screen (mine is a previous generation Prius tho)

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Old 26 Oct 2012, 03:19 am   #3 (permalink)
Daniel who wants to know
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Default Re: Calibration of MPG shown on 2010 Prius

> "VStarGuy" wrote in message
> news:8bd90$508955d1$42bb6765$18055@news.flashnewsg roups.com...
> Can the MPG amount shown be calibrated on a 2010 Prius?


Yes it can, but it won't be easy, by adjusting the fuel pressure slightly.
Displayed MPG is calculated based on miles driven, and fuel used. Since fuel
used is measured by total fuel injector "open" time if you change the
pressure the pulse width will be changed to compensate hence the displayed
MPG will change.

Reduce pressure, the ECM increases the long-term fuel trim, hence the
injector milliseconds, it thinks it injected more fuel, so the MPG number
goes down.

Increase fuel pressure and the opposite happens.

Since the fuel pressure regulator is in the fuel tank this will be
difficult.

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Old 27 Oct 2012, 11:08 am   #4 (permalink)
DA
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Default Re: Calibration of MPG shown on 2010 Prius

responding to
http://www.motorsforum.com/prius/cal...ius-11510-.htm
, DA wrote:
> me wrote:
> Yes it can, but it won't be easy, by adjusting the fuel pressure
> slightly.
> Displayed MPG is calculated based on miles driven, and fuel used. Since
> fuel
> used is measured by total fuel injector "open" time if you
> change the
> pressure the pulse width will be changed to compensate hence the
> displayed
> MPG will change.
>
> Reduce pressure, the ECM increases the long-term fuel trim, hence the
> injector milliseconds, it thinks it injected more fuel, so the MPG
> number
> goes down.
>
> Increase fuel pressure and the opposite happens.
>
> Since the fuel pressure regulator is in the fuel tank this will be
> difficult.
>
>


This sounds like an epitome of don't-try-this-at-home projects. I don't know
if the OP asked about something he/she could do him/herself but I would not
mess with fuel injector only to see the proper fuel gauge reading. After all,
you do have the second source of the same information - the MPG reading and
the miles since fill-up. Divide miles by MPG and you get the gallons used.
I've never been able to put more than 8.5 gallons in the tank and even then
the gauge showed the tank just about empty.

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Old 28 Oct 2012, 07:23 pm   #5 (permalink)
Daniel who wants to know
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Default Re: Calibration of MPG shown on 2010 Prius

> "DA" wrote in message
> news:13b5c$508c06e2$42bb6765$10433@news.flashnewsg roups.com...
>
> This sounds like an epitome of don't-try-this-at-home projects. I don't
> know
> if the OP asked about something he/she could do him/herself but I would
> not
> mess with fuel injector only to see the proper fuel gauge reading. After
> all,
> you do have the second source of the same information - the MPG reading
> and
> the miles since fill-up. Divide miles by MPG and you get the gallons used.
> I've never been able to put more than 8.5 gallons in the tank and even
> then
> the gauge showed the tank just about empty.



I didn't say anything about the fuel level gauge, just the average MPG
readout.

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Old 02 Dec 2012, 09:14 am   #6 (permalink)
Michael Dobony
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Default Re: Calibration of MPG shown on 2010 Prius

On Sun, 28 Oct 2012 19:23:44 -0500, Daniel who wants to know wrote:

>> "DA" wrote in message
>> news:13b5c$508c06e2$42bb6765$10433@news.flashnewsg roups.com...
>>
>> This sounds like an epitome of don't-try-this-at-home projects. I don't
>> know
>> if the OP asked about something he/she could do him/herself but I would
>> not
>> mess with fuel injector only to see the proper fuel gauge reading. After
>> all,
>> you do have the second source of the same information - the MPG reading
>> and
>> the miles since fill-up. Divide miles by MPG and you get the gallons used.
>> I've never been able to put more than 8.5 gallons in the tank and even
>> then
>> the gauge showed the tank just about empty.

>
>
> I didn't say anything about the fuel level gauge, just the average MPG
> readout.


That first assumes consistent inaccuracies, not random. Second, what effect
will changing the pressure have on power, emissions, and actual fuel
economy? Even if you could change the pressure, the effects could be
unacceptable.
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