MPG readout accuracy.

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RacerZX
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MPG readout accuracy.

Postby RacerZX » Sun Feb 11, 2007 7:54 pm

Can somebody please do a test and see how closely the computer's MPG display matches the real life data when you fill up? I.E. keep track of milage from fill up to fill up and divide the miles by the gallons you put in to see how closely that resulting number and the MPG display match?

I'm trying to figure out how much if at all my supercharger is skewing the MPG numbers, since fuel flow to that 7th injector isn't going to be metered by the ECU...


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mtbpath
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Postby mtbpath » Mon Feb 12, 2007 12:17 am

I am within .20.
my data is .20 higher vs the computer.

rlh2005
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Re: MPG readout accuracy.

Postby rlh2005 » Mon Feb 12, 2007 2:38 pm

Hope this helps

Code: Select all

Date    Miles     Gallons    MPG     TripCmp   price
8/7       0.0     12.555     0.0      UNK      2.799
8/12    145.1      9.555     15.2     14.9     2.779
8/15    380.0     20.767     18.3     17.2     2.749
8/25    268.5     18.684     14.4     16.0     2.579
8/27    261.6     15.810     16.5     16.1     2.569
9/1     169.4     11.257     15.0     15.8     2.489
9/3     387.3     19.827     19.5     16.6     2.589
9/10    333.5     20.868     16.0     16.3     2.359
9/18    300.0     18.032     16.6     16.4     2.119
9/23    179.3      9.447     19.0     UNK      1.979
9/26    365.9     19.919     18.4     17.0     1.939
10/1    118.1      7.738     15.3     16.8     1.919
10/2    284.2     14.953     19.0     17.2     1.8999
10/19   332.5     21.938     15.2     UNK      1.989
10/25   272.6     16.599     16.4     UNK      1.939
10/27    81.3      5.701     14.3     15.1     2.019
10/28   280.1     15.262     18.4     17.3     1.979
11/8    260.4     17.665     14.7     16.4     1.979
11/16   226.0     14.747     15.3     16.0     2.039
11/18   149.7      8.296     18.0     16.4     2.039
11/20   332.6     17.747     18.7     18.8     2.029
11/25    82.8      6.189     13.4     17.8     2.059
11/26   353.6     17.070     20.7     19.0     2.039
12/1    235.3     14.553     16.2     18.2     2.139
12/3    344.5     18.820     18.3     18.3     2.179
12/13   270.0     18.985     14.2     17.6     2.319
12/18   304.3     17.822     17.1     17.4     2.359
12/24   249.6     16.772     14.9     16.9     2.359
12/29   176.2     11.270     15.6     16.7     2.359
12/31   344.2     17.735     19.4     17.1     2.499
1/4     315.5     18.892     16.7     17.0     2.299
1/6     370.9     18.063     20.5     17.8     2.319
1/13    288.5     17.129     16.8     17.6     2.339
1/21    267.7     17.572     15.2     17.1     2.219
1/26     90.0      7.232     12.4     16.7     2.159
1/27    256.9     14.137     18.2     16.9     2.159
1/30    345.7     17.508     19.7     17.3     2.149
2/6     248.3     17.073     14.5     16.8     2.199
The MPG column is my miles drive / gallon fuel.

The TripCmp column is the trip computer's MPG calculation. Note, I do not reset the trip computer's MPG at refuelings. I'm trying to use it as a lifetime MPG. Granted, it was reset when the dealer repaired/replaced the fuel gauge sending unit.

Thank goodness, I have a PDA/Smartphone. I just enter the data in my cell phone at each fill-up.

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RacerZX
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Postby RacerZX » Mon Feb 12, 2007 3:05 pm

That doesn't help at all to know you have cheap gas! I pay almost $3/gallon for premium over here... :cry:

:wink:

jerry6
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Postby jerry6 » Mon Feb 12, 2007 5:26 pm

well 91 octane is 96 cents to $1.26 a litre here !! i wish i paid $3.00

rlh2005
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Postby rlh2005 » Tue Feb 13, 2007 11:51 am

RacerZX wrote:That doesn't help at all to know you have cheap gas!
If it's any consolation, the prices before 12/13 are 87 octane. :oops:

boogyman
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Postby boogyman » Wed Feb 14, 2007 7:56 am

Hey Racer, the computer is going to tell the average of the last little bit you traveled. So if you were putting along just before you got gas the computer will show something totally different than what was going on the rest of the time. So basically the computer is a useless display for MPG.

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RacerZX
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Postby RacerZX » Wed Feb 14, 2007 8:48 am

Hm, that's actually not my understanding. The MPG readout is the average since last reset, it's not a real-time display.

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phantom2
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Postby phantom2 » Thu Feb 15, 2007 3:51 pm

Racer,I think your interpretation of the "mpg" readout is correct

Middle Man
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Postby Middle Man » Thu Feb 15, 2007 4:48 pm

mtbpath wrote:I am within .20.
my data is .20 higher vs the computer.
That's quite similar to what I have experienced.

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blink32
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Postby blink32 » Wed Apr 25, 2007 9:55 pm

Figger I'll throw my 2cents in.
06 Path LE, Nismo intake, OME lift, 285/70R17 AT's @ 46psi, Yakima rack removed
CT to NJ @ 71-73 avg corrected MPH
Digi showed 16.9mpg over 207.8 mi trip
Actual was 17mpg over a corrected 222.4 mi trip

NJ to CT @ 65-66 avg corrected MPH
Digi showed 18.3 over 216.3 mi trip
Actual was 20.5mpg over a corrected 231.4 mi trip

Not sure why it was off so much going slower to CT but I double checked my numbers and set the timers/odo the same way both directions. And didn't do any calculations until I was home with all the numbers on my notes sheet. I posted the corrected numbers because my tires cause a 7% error on the speedo (assuming the stock size of 265/65R17 are 100% accurate). I'm going to redo the test probably next month when I go back up for the sake of consistency.

G35TR
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Postby G35TR » Thu Apr 26, 2007 10:19 am

I was curious about this myself, so I've been testing the mpg guage on the current tank (which is just about empty). I'll let you know my results after i fill up, which will probably be tomorrow.

Also, anyone else notice the HUGE difference between the first half of the tank, and the second half (according to the guage)?!?!

I got got about 190 miles out of the 1st half. I couldn't believe it. I thought to myself, that mpg guage is way off if I'm on par for almost 400 miles per tank!! Then the next thing I know, 100 miles later, my tank if almost empty. And there driving was the same throughout the entire tank.

Is it like this on all the Pathfinders??

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RacerZX
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Postby RacerZX » Thu Apr 26, 2007 10:25 am

Yeah, I've seen the same thing. Last 1/3rd a tank is only good for about 75-100 miles! :P

-c

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mtbpath
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Postby mtbpath » Thu Apr 26, 2007 11:13 am

RacerZX wrote:Yeah, I've seen the same thing. Last 1/3rd a tank is only good for about 75-100 miles! :P

-c
same, here. first half of tank does not equal to last half of tank.
the last half drops faster.
I average 200 on my first half but only get 100-125 on the last half.
it gives you a false sense to rely on the gauge.

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blink32
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Postby blink32 » Thu Apr 26, 2007 11:52 am

I don't know if you guys have seen the threads on the Australian boards but they are complaining of the same thing in the Gasoline models. Gauge and digi will read empty but they have something like 20 liters left (over 5 gals). I see the same issue. Apparently they are getting fixes for this over there. The diesels are fine though.

I see the same thing, last time I hit E and the digi gauge went to XX miles left I just kept on rolling for a solid 50 miles then filled up and still had something like a gallon & 1/2 left in the tank. Nissan either built in some rediculous safety margin or there is a problem with the in tank gauge.


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