[madan80]

Originally Posted by nitrous

What is the objective of the shaking??
How is it going to affect the car or FE??

I guess since you do a full tank to full tank - the extra fuel that you sneak in - will make you belive that your FE is good! (kiddin!!)

[pjbiju]

Originally Posted by nitrous

Do u have proof for this,dadu?

As the quantity of the fuel in the fuel tank decreases, there is greater room for the fuel to move around, as you drive. This increases the evaporation of the fuel.

Therefore, it is better to fill up the tank, once it has reached the half-empty level.

[balaji_n29]

SX4 owner's manual states not to fill in petrol after auto cutoff. The reason stated is the expansion of fuel at hot weather and the need for space for fuel to expand. So I might as well stick to this. I don't know if other cars have such info in the owner's manual. Better to check the owner's manual.

My 2 cents.

[agent4ferrari]

it helps trapped air pockets to come out and hence create larger usable volume inside the tank.

[binoy_tharakan]

When we fill fuel the fluid reaches the tank via an inclined pipe.

Did you notice when filling a kerosene stow with a funnel we may have to raise the funnel a bit to let the air from the stow to escape? We cant take the pipe that runs to the fuel tank to let the air trapped inside the tank to escape! Thus it may require to shake the vehicle a bit so that there will be gap within the pipe itself and the air comes out via that.

Bus and truck can't be shanked so they wait and when the air trapped come out as bubbles via the pipe (which takes bit longer time than the shaking funda!)

It is never been advised to fill your tank by shaking it because the petroleum products emits gas when its heated and all the fuel tank will have some space to accommodate the additional gas during hot days. If you shake and fill fuel you are actually eating up the free space in the tank.

[pjbiju]

Fuel tanks on every vehicle have a small opening either incorporated into the fuel tank caps or as a separate pipe that opens out into the open. This is to let the fumes and vapours escape and to let air into the fuel tank to prevent the tank from collapsing as the fuel is being consumed.

[nitrous]

Originally Posted by pjbibu

As the quantity of the fuel in the fuel tank decreases, there is greater room for the fuel to move around, as you drive. This increases the evaporation of the fuel.

This isn't proof.This is what ur mind thinks!

[pjbiju]

Originally Posted by nitrous

This isn't proof.This is what ur mind thinks!

Hi Nitro,

I thought the scientific explanation behind this was simple enough. Let me make an attempt to do that.

"Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously becomes a gas (e.g. water vapor), without being heated to the boiling point.

The reason a liquid evaporates is that its molecules are all in motion in nearly random ways and speeds, and the energy of that movement can be compared to the heat needed to boil that liquid. On the average, none of them have enough energy to be considered "boiling", or else the liquid would turn into vapor quickly. But when the molecules collide, they transfer energy to each other in varying degrees, based on how they hit. Sometimes the transfer is so one-sided that one of the molecules ends up with enough energy to be considered past the "boiling point" of the liquid. If this happens near the surface of the liquid (where it meets some gas), it may actually fly off into the gas, thus "evaporate".

So petrol moving around in the tank will evaporate more quickly.

Again, volatility in chemistry is a measure of the speed at which a chemical element or chemical compound evaporates. Higher volatility indicates faster evaporation and a lower volatility means it will evaporate more slowly. Petrol is highly volatile."

You can perhaps do a practical experiment by taking some quantity of petrol in a pan and then leave it in the open to evaporate. Measure the time taken for the petrol to evaporate. Then take the same quantity of fuel in the same pan and then keep shaking the pan vigorously to emulate "a car being driven" and then measure the time taken for the petrol to evaporate.

p.s. some definitions are from wikipedia.

[binoy_tharakan]

Originally Posted by pjbiju

Hi Nitro,

I thought the scientific explanation behind this was simple enough. Let me make an attempt to do that.

"Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously becomes a gas (e.g. water vapor), without being heated to the boiling point.

The reason a liquid evaporates is that its molecules are all in motion in nearly random ways and speeds, and the energy of that movement can be compared to the heat needed to boil that liquid. On the average, none of them have enough energy to be considered "boiling", or else the liquid would turn into vapor quickly. But when the molecules collide, they transfer energy to each other in varying degrees, based on how they hit. Sometimes the transfer is so one-sided that one of the molecules ends up with enough energy to be considered past the "boiling point" of the liquid. If this happens near the surface of the liquid (where it meets some gas), it may actually fly off into the gas, thus "evaporate".

So petrol moving around in the tank will evaporate more quickly.

Again, volatility in chemistry is a measure of the speed at which a chemical element or chemical compound evaporates. Higher volatility indicates faster evaporation and a lower volatility means it will evaporate more slowly. Petrol is highly volatile."

You can perhaps do a practical experiment by taking some quantity of petrol in a pan and then leave it in the open to evaporate. Measure the time taken for the petrol to evaporate. Then take the same quantity of fuel in the same pan and then keep shaking the pan vigorously to emulate "a car being driven" and then measure the time taken for the petrol to evaporate.

p.s. some definitions are from wikipedia.

Fine Biju,
Good explanation. But what is the fact that you are proving? A car filled with fuel till the brim is an advantage? So the "shaking stuff" happening at pump has a positive impact. But how can some one keep the car always full fuel (till the brim). The theory you said will be advantageous only till some empty space form in the tank.

[shapath]

even after informing the guy who is filling there were times when fuel is popped and they say , sir AIRLOCK sir & it is JUST A BIT sir.
what one has to do TO AVOID THIS airlock issue.( if at all that is the issue.) anything to be noted for SANTRO just in case to be more safe and avoid wastage. this POP up/wastage has happened even when "fill till auto lock" situation. TIA

[abhijit 2284]

generally diesel when filled causes a lot of air bubbles versus petrol ( must have something do with their properties) so either they shake the vehicle to liberate the air or the second option would be to fill it much more slowly which would be irritating for the operator as it would put a lot of pressure on his hand.
i generally ask the operator to fill till auto shut off and then fill it to the next round-up figure