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Old 01-03-2009, 04:16 AM   #1 (permalink)
hummingbird
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Join Date: Dec 2008
Location: Noida, UP, India
Posts: 197

City - '04 Honda City iDSI EXi
90 day: 47.47 mpg (US)
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Effect of ambient temperature on fuel tank volume

Hi folks,

I am about to log in my first results of a well-driven tank - I have got around 6 L/100 km, on a 1.5L 5 speed manual tranny Honda City. But when I get into the method of getting to my exact FE data, there is problem - as I think -

The SOP for finding FE is Tank up till clip off - reset trip meter - drive around till empty (of course almost empty) go back to the same pump, same orientation - tank up again till clip off - note amount of fuel pumped - note trip meter - divide fuel x 100 by trip meter reading to get L/100 km reading

But here, if there is significant temperature difference between when you tanked up earlier, and now, you will get less gas in the tank when filling up now (relatively colder ambient - shrinkage in the tank volume - less fuel to clip-off). The change in ambient temperature is because I filled my tank in Nov, and now it is almost Jan (quite a stretch in my refilling routine, because of hypermiling techniques, I should admit! )

Would that result in erroneously higher tank mileage? ( i think it will...) Should the SOP be modified? Any ways to calibrate out this error?

Wish you all a happy and fulfilling new year 2009!

PS: How can we prevent the spell check to highlight 'hypermiling' as a spelling mistake when posting? It is so embarrassing...

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