quote:Originally posted by PanteraDoug:
OK. This discussion brings up two more subjects that I see.
1) on Tennessee Tims plumbing system with the Weber carbs and a return line to the tank, how do you protect the carbs from receiving more than 3-4 psi of fuel if the regulator is behind them and not in front of them?
2)considering that we are returning hot fuel to the tank with the return line, how do you protect the tank itself from being susceptable to a flash explosion? Particularly considering that liquid fuel under pressure is going to have a tendency of atomizing, i.e., mixing with the air into a combustible mixture?
This is what I was saying about using the fuel tank itself and it's contents as a heat sink.
I understand that the EFI systems use this but I don't just go and presume that all is well and good.
What happens when the tank is nearly empty and you are spraying hot fuel back into the tank? The Pantera tank is in VERY CLOSE PROXIMITY to the exhausts?
I don't know if this is of any help at all but on my fuel injected setup a large amount of fuel (enough for maximum speed and maximum load) is always being fed to the injector rails all the time.
Most of it (99%) when at idle and driving slow like city driving will be returning to the tank.
This returning fuel is hot. it has just traveled through all the pipework, pumps and filters in the engine bay and it picks up a lot of heat.
If you feel the fuel tank after a drive you can feel it is quite warm. The tank is being used as a heat sink to remove that heat from the fuel.
Is this dangerous ?
Hot returning fuel would vaporise in the tank producing vast amounts of gasoline vapors, there would in fact be so much fuel vapor the "air" in the tank would consist mostly of that and there would be almost no oxygen. The "air" in the tank is so rich it will not burn.
Fuel vaporising in the tank both makes the atmosphere in the tank extremely rich and also pushes any air that was in the tank back out the breather to atmosphere.
I use one of the fuel tank caps that has pressure relief valves in it rather than just a straight breather hole. It allows air in only if the pressure inside the tank falls to a certain point.
I find it does not let air in while the car is running. That is because the vaporising fuel is actually pressurizing the tank and it does not require outside air to replace the volume of the fuel being used. the volume of fuel being used is being replaced by fuel vapor !! If the pressure gets too high (1 psi) it allows vapor to escape to atmosphere.
When the car is switched off and is left to cool down the gasoline cools and the vapors condense and the valve in the cap does allow air to enter the tank from atmosphere. This would allow oxygen into the tank but now the car is not running and is cold. When it is started and warms up the fuel once again heats up and the fuel vapors push the air back out and the "air" in the tank becomes super rich with fuel vapors again.