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Old 30th January 2010, 03:00   #1
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Lightbulb Modifications to the fuel tank to improve FE

I am having this idea of a fuel tank, which I think will add to FE of all vehicles.

Fact: A standing car- Fuel loaded, continuously looses its fuel owing to vaporisation property of the fuel.
Idea: Lets not allow that!

Method:
I suggest we have a expandible Poly-Ethylene (high grade Plastic) forming a baloon like structure inside our fuel tank, the sack-type-balloon will inflate enough to allow a full tank fuel volume, and deflate with fuel-depletion (fairly elastic, I mean to say)
The balloon sack will have
-vent- (for venting/only at filling time),
-filling end ( for fuel in )
-discharge end (fuel out of fuel tank- to fuel pump/carb)
The tendency of the balloon will be to empty its contents, hence keeping the fuel under slight positive pressure at all times.

The tank can still be stock!

I am making some drawing of the same. (simplified)


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Old 30th January 2010, 17:32   #2
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You can't stop fuel from evaporating. You can only reduce its "rate of evaporation". This can be done by reducing the temp of the liquid and keeping it in a vaccuum.

By filling fuel when its cold outside and filling it to the brim can help improve fuel economy without having to make any alteration to the fuel tank.

The flexible balloon will work to a certain extent since it will maintain a higher level of vaccuum compared to a rigid tank.

Shan2nu

Last edited by Shan2nu : 30th January 2010 at 17:36.
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Old 30th January 2010, 18:23   #3
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Cool The balloon will actually keep a positive pressure

I was saying that the fuel will be inside the balloon!
And, sure we can avoid any evaporation/vapourisation !
Lets keep no contact between the fluid and the air, and the balloon will also add to the insulation effect per se' !

the vent can be again fed to the carb/air intake side as supplement air too !! ( that was my mod to the original !)

and I think it sure will add to the FE 10+percent.. depends on the running/filling patterns/standing time/ambiente' temperature !!

@shan2nu
thank you for bringing up the pressure point..

So, how does that sound?

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Old 1st February 2010, 09:38   #4
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Here are a few points that work against your idea:

1) you still need a metal casing for safety purposes
2) Plastic is not elastic in nature hence ruled out
3) Rubbers harden over a period of time ruled out
4) Well a good fuel tank with proper hoses and a decent tank cap does not allow the petrol to evaporate until it reaches a particular pressure, hence keeping the gaseous petrol inside the tank.
5) A balloon kind of structure will not be centrally positioned hence will add to the de-stability of the car based on the fuel in it
6) you could run a fuel pump agree but what about fuel level only option is weighing, again wont work as the balloon can not be positioned in one place
7) Again "The tendency of the balloon will be to empty its contents, hence keeping the fuel under slight positive pressure at all times." would mean flooded carbs if you park for a longer duration i don't think it will make a difference in case of an MPFI car
8) It cannot give you a long life as elasticity will reduce over a period of time.
9) Your statement "and I think it sure will add to the FE 10+percent.. depends on the running/filling patterns/standing time/ambiente' temperature !!" is so a guestimate that it does not even begin to make sense.

Hence I still believe in point 4 more than anything else. so stick to the original fuel tank.
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Old 1st February 2010, 09:54   #5
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A similar equipment is being used in racing for an altogether different purpose. It's called a fuel cell bladder, its kept inside a metal casing.

Race Car Fuel Cell Methanol Fuel Bladder Photo
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Old 1st February 2010, 10:04   #6
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I am not sure whether the fuel can flow if the tank does not breath.
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Old 1st February 2010, 12:49   #7
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Quote:
I am not sure whether the fuel can flow if the tank does not breath.
A tank needs to breath only when its rigid, since its volume remains the same irrespective of the amount of fuel inside. But a flexible material like a rubber balloon will expand and contract wth rise and fall in fuel level. The only prob with this is, how do you measure the fuel inside the tank if the volume is not constant? Hehe

Instead of all this. Why not just have a vaccuum pump for the fuel tank. You fill whatever amount of fuel you need, switch the pump on and remove all the air inside the tank. (Like those vaccuum food storage containers we get).

With no air inside, the evaporation process will drastically reduce and ambient temp inside the fuel tank will also be lower than normal. We could also use some sort of a device which will prevent the fuel from splashing around inside the tank, further reducing the chances of evaporation. I think race/sports car are already using this to prevent fuel from flowing to one side of the tank when conering.

I rem Wolf having to abandon his track session midway due to the fuel moving away from the fuel pump inlet cutting off the fuel supply to the engine, everytime he cornered hard. I filled another 10ltrs of fuel in the car before my session and faced no issues.

Shan2nu

Last edited by Shan2nu : 1st February 2010 at 12:56.
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Old 1st February 2010, 12:55   #8
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Isn't the fuel pump/motor an immersible pump and located inside the tank ? How will this work ?
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Old 1st February 2010, 12:59   #9
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With vacuum inside the tank the fuel will not flow. Also vacuum ought to aid evaporation, fuel vapour has lots of space to occupy.
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Old 1st February 2010, 13:10   #10
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My 2 Cents :

The amount of money spent in the making & maintaining such a Elastic balloon (as it may have leaks & other issues) will certainly over run the price of the fuel which is lost due to eveporation currently. SO the first question is Does it make economic sense.

How much fuel do you think we loose due to evaporation normally. I dont think it is that a great amount.
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Old 1st February 2010, 13:19   #11
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It was mentioned somewhere here that having a sort of "floating cover" on the fuel surface to prevent evaporation is compulsory as a part of Euro IV compliance.
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Old 1st February 2010, 13:29   #12
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Quote:
Originally Posted by SamtheLeo View Post
The amount of money spent in the making & maintaining such a Elastic balloon (as it may have leaks & other issues) will certainly over run the price of the fuel which is lost due to eveporation currently. SO the first question is Does it make economic sense.
+1 to that. The amount of fuel lost due to evaporation is very less if the vehicle is parked under shade and kept at a cool place. There is no point in over researching the issue here.
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Old 1st February 2010, 13:31   #13
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If the baloon has peizo electric strands in them then,
1> depending on the amount of strain they will out put a certain amoutn of electricity. that way the amount of fule can be checked.

2> if current is applied to the strands then they can be made to contract, hence negating the requirement of a fuel pump.

A cut of valve can be put to further restrict the amount of fuel flow.

But the fuel could continue to evaporate inside the baloon, creating an vapor bubble which will throw off the fuel gauge.
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Old 1st February 2010, 13:34   #14
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Quote:
With vacuum inside the tank the fuel will not flow. Also vacuum ought to aid evaporation, fuel vapour has lots of space to occupy.
Oh yeah!! What was i thinking!!

Then i gues another way would be to reduce surface area of the fuel inside the tank.

Shan2nu

Last edited by Shan2nu : 1st February 2010 at 13:37.
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Old 1st February 2010, 14:02   #15
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This resembles an Accumulator used in Turbine governing systems. THe accumulator has a baloon inside, which is filled with NItrogen which in the event of a sudden pressure drop inflates and pushes the oil into the system.
The problem in car fuel tanks would be whether the fuel can press against the gas pressure of the baloon.
Any how try.
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