Why does my on board computer tell me my average MPG is over 30 when at the pump its 21? I didnt expect it to be stop on, but 50% more than what my actual is was alittle supprizing.

 

How are you arriving at 21?

 

number of miles driven on the tank/gallons of gas put into tank.

 

Is it possible that the two common types of gallons are being interchanged?

if you put into google's search engine:

30 gallons in imperial gallons

you get:

30 US gallons = 24.9802153 Imperial gallons

At one time, the British gallon differed depending on what you were measuring, and where you were measuring it. But, by the 19th century, two definitions had survived: the Queen Anne (or Wine) gallon, which was 231 cubic inches, and the Winchester (or Ale) gallon, of 282 cu in.
In 1824, the British abandoned both the Ale and the Wine gallons in favour of the Imperial gallon, based on the volume of 10 pounds of water (which works out at 277.41945 cu in). America, by this time, had already standardised on the Wine Gallon of 231 cubic inches (strictly speaking, this was defined as the volume of a cylinder 6 inches long and 7 inches in diameter, or 230.9070 cubic inches).
The result is that the US gallon is 83.267% of the British gallon.

read this and more at:

http://www.miketodd.net/encyc/measures1.htm

 

Hum, that is odd. Any reason why it would not be set up for US gallons? Can i reflash the computer somehow? What does the dealer do if they install JCW injectors, just say goodbye to the computer?

 

Did you try resetting the computer to zero and testing again over a couple tanks worth of gas? Just press and hold the computer button on the blinker stalk for a few seconds until it resets.

 

I am testing tank two right now.

 

Each Mini is calibrated to the original country of shipment so if the car was shipped to Us it would be set for Us gallons,Canada Litres/100 klm etc.If your car is us shipped to Us reset computer and try again.Remember 2-3 tanks is necessary to get average because you cant get accurate based on 1 tank.

 

I understand that. Do you mean i shouldnt recalibrate if for each tank? I reset both 1 and two when i bought the mini, only one of the two do i reset when filling up. The overall gauge says i should be getting 29.7

 

I reset average for each tank. I like to see what I'm getting on each tank so that I can decide what fuels and driving styles works best. I did a manual calculation after the last tank and compared it to the OBC.

OBC: 30.9mpg
calc: 32.97mpg

I always squeeze once to top off, but I cannot guarantee that I fill the tank to the exact same level on each fill-up.

What do you mean by your statement of resetting one and two? I hit the trip-odometer and the average mpg buttons, reset them, and leave the average speed alone.

I can't imagine a reason in the world for any car to come prepared to measure fuel in imperial gallons. That would be like setting your speedo to measure in king's miles / hour. I highly doubt this is the case.

If you measure such a disparity again, take it to the dealership for a diagnostic.

 

It may be calibrated to the EPA's findings on MPG, which has always been a bogus number.

 

My OBC runs consistantly 10% optimistic, and ranges +/-5%.

ahamos - Nav cars come with dual MPG counters. Like JPalt, I use the #1 for current tank mileage, and #2 for long term.

 

Well i will run a few more tanks through, if it continues to be off, back the the dealer i go.

And yes, i have the nav which gives you a 1 and two.

 

Well my OBC says I do 26.5 mpg... when I really do about 22... And happy I know I’m heavy on the gas… he he

 

Interesting thread... my OBC says 24, and my napkin math says 24 as well. Wish it were higher, but I live a mile from work and drive an S. I figure my poor engine hardly ever gets warm.

 

It appears that there is a way add correction factors for the MPG that is reported by the OBC. Take a look at Test 20 in THIS MINI2 FAQ.

Theo

 

(edit: Koopah - you beat me to the post !!!!)

and make an adjustment to calibrate the computer to correct consumption IF you know how much gas is actually in the tank and what your consumption is...

(To be clear it is actually one tank with a saddle like construction.)

See sections 6 to read values, and 20 to store a "correction factor"

from Mini2.com under the FAQ & DIY heading:

1. With the key in the ignition, but in the off position, press and hold down the odometer reset button, while holding the button down, switch the key in the ignition to position 1.
2. The screen will say 'Test' and a number.
3. Scroll through, (pressing reset button) through to test 19 and wait a moment.
4. Wait and the message will say "log i-off" then "log i-on" and back to "log i-off" again. When "log i-off" appears, press again. You are now in the system. (Woooo)
5. You can (if you wish) start the ignition any time from now.
6. Scroll through to test 7.0 (or whichever from the list below) and wait a moment, after a pause you will enter the test 7.* range of information.
7. You can scroll through now (7.1,7.2,7.3 etc.) using the reset button.
8. You can exit each menu by pressing, holding for a few seconds, then releasing the reset button.
9. To leave the system scroll to 19 and leave it for a few moments.
   Switching off the ignition also exits the system.

Test:

1.0 Chassis number
1.1 Kilometer count
1.2 Parts number
1.3 Coding-, Diagnostic- and Bus-index
1.4 Production Date (Calender week/year)
1.5 Hard- and Software status
1.6 Injectorstatus, Cylinder count, Engine factor.

2.0 Combisystem Test

3.0 Service intervall counter

4.0 Actual fuel consumption in l/100km. eg.0154 = 15,4 liters/100kms.
4.1 Consumption in liters/100kms.

5.0 Distance consumption in l/100kms.
5.1 Actual rest distance with available fuel in Kms.

6.0 Actual amount of fuel in tank. eg. 123321 =12,3liters left 32,1 liters right
6.1 Total amount of fuel in tank.
6.2 Show value of Fuel guage. 1= both senders OK, 2= sender failure, 3=ti signal unplausible (no reading)

7.0 Actual coolant temp.
7.1 Actual outside temp.
7.2 Actual engine revs.
7.3 Actual speed

8.0 Hexadecimal readings of menu 7.0 to 7.3

9.0 Actual on board voltage (Battery)

10.0 Land codes

11.0 Unit codes

12.0 No funktion

13.0 Gong test

14.0 - 14.4 On board diagnostic codes. eg 000000 = no failures

15.0 - 18.0 No funktion

19.0 On/Off for Test menu.

20.0 Correction factor for Fuel consumption
Formula for correction:
Shown consumption x 1000 / user defined consumption
Push the trip reset button to begin the correction. Numbers count up from 0-9, when correct number shows push trip reset button.

20.1 Sets 10ths. for consumption factor
20.2 Sets 100ths. and 1000ths. for consumption factor
20.3 Saves the new consumption factor and shows new value

21.0 Software reset. (Same as disconnecting battery)

Notes:

I have not been able to get speed into MPH, if you can update me with how to do this (if it's possible), then feel free to do so.

Your MINI's computer may give more or less information than stated above.


Hope this helps, there is a light show that you can test all the LED's on the interior of the car instrumentation which I love to do at night to show first timers....

Have fun and good luck...



btw, I have my car in the garage with 1 mile worth of gas left in it... Next time I drive it, I have to get gas right away!!!

 

That seems too complex for me

Also, i noticed on MINI2 that was for the odometer, has anyone tired it with the nav?

 

Interesting. I haven't checked in a while, but when I first got the car, I was checking pretty regularly and my OBC was almost always within about 1/2 mpg of my calculations. This is an Oct '04 build 2005 MCS, with no mods.

I've noticed that my mpg has gone way down lately, but there's a very good reason for that! I recently installed a CAI and a Milltek cat-back exhaust. Can't keep my foot off the gas!

I wonder if these mods will cause a change in the accuracy of my OBC?