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Calibration of MPG shown on 2010 Prius

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Posted by VStarGuy on October 25, 2012, 3:08 pm
 
Can the MPG amount shown be calibrated on a 2010 Prius?

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Posted by DA on October 25, 2012, 4:08 pm
 
responding to
http://www.motorsforum.com/prius/calibration-of-mpg-shown-on-2010-prius-11510-.htm
, DA wrote:

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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Posted by Daniel who wants to know on October 26, 2012, 8:19 am
 
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.


Posted by DA on October 27, 2012, 4:08 pm
 responding to
http://www.motorsforum.com/prius/calibration-of-mpg-shown-on-2010-prius-11510-.htm
, DA wrote:

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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    _________|__( )__|_________
        x/ _| |( . )| |_ \x
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Posted by Daniel who wants to know on October 29, 2012, 12:23 am
 
I didn't say anything about the fuel level gauge, just the average MPG
readout.


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