fuel gauge

[agmgranturismo2006]

my fuel gauge moves slowely from full mark to the middle mark and after the middle mark moves faster to the empty mark
from full to middle the car makes 250kms so why the fast drop in the gauge after the middle mark by the way the car makes 500kms in the 50 liter tank capacity that equal 10 km for every 1 liter

[PhatRoyale]

That's not how you calculate fuel economy. Reset your trip odometer, fill up all the way and keep track of your mileage the next time you fill up.

Enter in your information here. It will calculate your real fuel economy. Or just a site like fuelly or spritmonitor to keep a running tally like the one in my sig.

http://oee.nrcan.gc.ca/transportatio...ator-input.cfm

[agmgranturismo2006]

Originally Posted by PhatRoyale

That's not how you calculate fuel economy. Reset your trip odometer, fill up all the way and keep track of your mileage the next time you fill up.

Enter in your information here. It will calculate your real fuel economy. Or just a site like fuelly or spritmonitor to keep a running tally like the one in my sig.

http://oee.nrcan.gc.ca/transportatio...ator-input.cfm

i do what you said for clculating the fuel economy but my question is why when the fuel needle moves fast down when it reaches the middle mark also rises when going uphill

[trife96]

as long as it reads empty when its empty...thats the main thing...when i swapped my gage cluster with one for a tach, I now have that prob...but when its low its really low, and thats all i cared about.

[Bitter]

because you have a float inside, when the fuel moves in the tank the float can move also.

[Hiro Protagonist]

What the gauge is actually registering is fuel level, not fuel volume. Since the fuel tank isn't a perfectly regular shape, the level doesn't decrease consistently with fuel usage.

Think of a bottle which has a long thin neck - put it under the tap and turn the tap on so you get a constant stream of water. Notice how the level in the bottle goes up relatively slowly in the bottom of the bottle because it is wide, but as the level reaches the narrow neck it rises faster and faster (despite the same flow of water in)? This is basically the opposite of what is happening in your fuel tank. The top of the fuel tank is big and wide, so the float (and needle) will drop slowly as a change in volume only slightly decreases the level. As the level in the tank decreases, the shape of the tank changes and causes the level to drop faster, hence why the gauge drops faster in the bottom "half" of the tank.