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  #1  
Old 11-05-2005, 07:48 AM
Ridiculously Active Enthusiast
 
Posts: 839
Default Accuracy of the Prius II MFD MPG

I started keeping track eight tanks ago.

By the pump, I have used 73.920 Gallons, while the MFD calculates out to 72.975 Gallons.

The last tank is always a loose end that will be mitigated as the numbers increase, but as of now actual consumption is 1.3% greater than MFD.

This is in line with other reports of ~ 1.5 - 2.0% overestimation of MPG by the MFD.

.


R2-E2
, 2G Prius.
Highway/City/Husband/Wife MPG: 56.5, as of 12/2005, 26K miles

Jac Nasser, Ford President: "We are planning to launch a hybrid version of
this car [P2000] within this year [1998]. We will also make FCEV available in
2004."
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  #2  
Old 11-05-2005, 09:52 AM
Clubford00's Avatar
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Real Name: Dean
Location: Buffalo Grove, Ill
Hybrids: 05 Toyota Prius, Super white
Posts: 147
Default Re: Accuracy of the Prius II MFD MPG

some people have way too much time on their hands...

.

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  #3  
Old 11-05-2005, 08:29 PM
Schwa's Avatar
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Real Name: Erick
Location: Coquitlam, B.C.
Hybrids: 2001 Prius
Posts: 1,045
Default Re: Accuracy of the Prius II MFD MPG

Personally I think the reason it's inaccurate is that it only samples data every second or two. When you first press the gas pedal, that's when fuel consumption is at it's worst, but the MFD usually misses the initial acceleration and only sees the data after the car is moving significantly. This is balanced out on the other end by the MFD seeing fuel consumption for a bit longer than the engine is actually running for, but because that's a much smaller fraction of fuel consumption it's not a balanced system, as far as accuracy goes.
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  #4  
Old 11-06-2005, 08:57 AM
xcel's Avatar
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Real Name: Wayne Gerdes
Location: Northern Illinois
Posts: 2,567
Default Re: Accuracy of the Prius II MFD MPG

Hi Schwa:

___Remember Ken1784ís SuperMid display in Krousdbís 04 Prius II? It would report FE almost dead on vs. the 1.5 mpg overestimation of the Prius IIís OEM FCD and they are both tied into the same ECU taps. Some of us had a small discussion that Toyota may have actually biased the FCD in the MFD this way for whatever reason(s).

___Good Luck

___Wayne R. Gerdes

.




Last edited by xcel; 11-06-2005 at 10:12 AM.
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  #5  
Old 11-06-2005, 08:29 PM
Schwa's Avatar
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Real Name: Erick
Location: Coquitlam, B.C.
Hybrids: 2001 Prius
Posts: 1,045
Default Re: Accuracy of the Prius II MFD MPG

The SuperMid tapped directly onto the fuel injection signals, plus I'm sure it sampled data continuously rather than every 2 seconds like the stock MFD. It would be nice if Toyota could make it more accurate, it's just a matter of tweaking the code a bit so that it agrees with the real useage.
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  #6  
Old 11-07-2005, 12:59 AM
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Location: Yokohama, JAPAN
Hybrids: 2004 Prius
Posts: 499
Default Re: Accuracy of the Prius II MFD MPG

Quote:
Originally Posted by Schwa
The SuperMid tapped directly onto the fuel injection signals, plus I'm sure it sampled data continuously rather than every 2 seconds like the stock MFD. It would be nice if Toyota could make it more accurate, it's just a matter of tweaking the code a bit so that it agrees with the real useage.
I don't think the stock MFD does not measure such rough 2 seconds intervals.
The MFD data is very stable and relatively accurate, but it just did not calibrated well.

The displayed mileage value is always within 2% plus or minus 0.5% which is I would like to say accurate.

Ken@Japan
http://priusdiy.fc2web.com/
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Old 11-07-2005, 12:59 AM
 
 
 
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