Re: [DML] Overheating Fuel Tank. (Long!)

["Walter Coe" <Whalt@xxxx>]

> I really don't want to replace the existing aluminium
> pipes with rubber hoses. This just worrys me in as it's two more
> items that I have to worry about rotting/replacing in the years to
> come.

You are underestimating the quality of modern silicone hoses. I have read
accounts of police departments equipping all of their patrol cars with
silicone hoses and not ever having a failure in any of them. Hey, I saw it
on the internet, so it must be true. :-)

> I'm currently working on a way
> to not only remove the spring from the equasion, but the entire
> pickup hose as well.

That may be well and good, but unless you are installing a wert cooler (from
beer brewing fame) or a second fuel pump in series, it probably won't be any
better than the OEM suction hose & baffle.

> 2. The coolant pipes on both sides of the radiator are transferring
> heat thru the fuel. Gasoline is absorbing heat from the source
> pipe, it then travels thru, and is reabsorbed by the cooler return
> pipe.

I see your point, but I disagree. Until the fuel temperature is equal to
the coolant temperature, the net effect is that both pipes are going to heat
the fuel. And if the fuel temperature ever reached the coolant temperature
on a hot day, then fuel pump noises will be the least of your worries.

> Does heat directly transfer from the water pipe into the
> gastank? Or, is the heat absorbed thru the plate below
> protecting the gas tank?

This is an interesting thought, but again I disagree. Look at the big
picture: surface area. There is more tank surface area in proximity to the
pipes than there is pipes to cover plate. And there is way more tank
surface area in proximity to the cover plate. Hence, the plate probably
draws more heat from the tank than it puts into it.

[concerning heat sink compound]
> Don't laugh just yet, that may just be the thing we need. I don't
> know how we could attach fins to the bottom plate, but it should
> do the trick to rid the tank of excess heat. The only question I
> would have is how well does the compound adhere to things?

It doesn't. It is typically a thick viscous (and messy) white paste. When
I removed the fuel tank from my car, I discovered a triangle-shaped piece of
black cloth between it and the cover plate. Since my TankZilla leaked fuel
all over, this cloth was rotten. When I put it all back together, I stuck a
sheet of gasket paper in there to make up for leaving the original out. I
can't say what the purpose is other than maybe to stop the tank from
chaffing against the plate.

> I don't think that a fuel radiator of any sort sould be nessiasry at
> all. <snip>
> Rather than trying to keep hot
> fuel cool, let's keep the fuel from getting hot at all, and use the
> heat sink on the bottom to rid the gas of any stray heat that may
> have entered.

I like your enthusiasm, but I think you are jumping to conclusions. A heat
sink is a heat sink. As long as it transfers heat away from the fuel, it
doesn't matter where in the system it is. The fuel tank itself is not a
good conductor of heat, and anything next to it is not going to transfer
heat well (coolant pipes excepted because of the extreme temperature
gradient). If you want to make it into a good heatsink then replace it with
a metal tank. The extreme of this idea is to make the fuel tank into a Ford
Pinto's trunk turned upside down. Make the cover plate the bottom of the
fuel tank. Put ridges in it, and it will probably make an effective heat
sink. But it would be a lot easier to plumb in a fuel radiator.

> Although if we insulate the water pipes, and
> remove the pickup hose to kill the noise, we may not even need
> to go to that far of an extreme with the bottom plate.

I am certain that the problem is not the pickup hose. The noise comes from
fuel boiling in the pump similar to fuel boiling in the engine compartment
causing a hot start problem.

Hot & under pressure = stable.
Hot & at atmospheric pressure in engine compartment = vapor lock hot start
problem.
Hot & under vacuum inside fuel pump = cavitation / vapor lock boiling fuel.

Now for some late breaking news:
My thermostat was sticking closed (or mostly closed) which on hot days
caused the temperature indicator to normally hover just below the center
(220F) mark (too hot). Now with the new thermostat from PJ Grady installed,
it hovers around 1/4 scale. Lower coolant temperature means that heat
transfers to the fuel tank at a slower rate which means that I can do a lot
more driving before the fuel pump cavitates. In fact, I have done a lot of
driving since with a near empty tank on hot days with no more cavitation
noises at all! But time will tell. The weather has cooled off a little
lately. How hot does your engine normally run?

Again, my strategy is to some day install a fuel radiator. If there is some
radiator air flowing over the top of the fuel tank, then perhaps this would
be good location for a fuel radiator. It has air circulation and is a
relatively secure spot, albeit cramped. If that don't cure it or if I feel
I need larger coolant pipes due to an engine swap (ala Bob Brandys) then
I'll make a stainless fuel tank with more room for the pipes & insulation.

Walt