So I was wondering why someone hasn't come up with a additive to help with vapor lock/boiling gas. I sure would think there's a market for it.
Anti boil additive
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Ranger16
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My guess is that it would end up being detrimental to combustion.
Any liquid, water, gasoline, anti-freeze, has a natural boiling temperature. With the cooling liquid
in your radiator, the radiator cap is designed to keep about fifteen pounds of pressure on the
contents of the cooling system to keep the coolant from boiling at 212 degrees. Each pound of
pressure put upon the liquid raises the boiling point approximately three degrees. Fifteen pounds
translates to water boiling at 257 degrees. Gasoline boils around 181 degrees, and while a
carbureted engine would have the gasoline start to "Perculate" around this temp, a fuel injected
car would not because of the added pressure in the fuel system. Purty neat Eh? Shittier gas,
lower boiling point. More pressure, higher boiling point. Not a lot of cars with carburetors now.
in your radiator, the radiator cap is designed to keep about fifteen pounds of pressure on the
contents of the cooling system to keep the coolant from boiling at 212 degrees. Each pound of
pressure put upon the liquid raises the boiling point approximately three degrees. Fifteen pounds
translates to water boiling at 257 degrees. Gasoline boils around 181 degrees, and while a
carbureted engine would have the gasoline start to "Perculate" around this temp, a fuel injected
car would not because of the added pressure in the fuel system. Purty neat Eh? Shittier gas,
lower boiling point. More pressure, higher boiling point. Not a lot of cars with carburetors now.
return hose from a regulator next to the carb?
PurpleBeeper
Well-Known Member
Yes, that is what 5.7hemi is saying.
Also, you gave a very good description of why "vapor lock" is much less of an issue with fuel injected engines (much higher fuel pressure = much higher fuel boiling point)….good job.
Also, there's a little thing called "Raoult's Law". In a nutshell, it says that the only real way to keep fuel from boiling is to have a less volatile blend (in other words, gasoline that's more like diesel fuel than gasoline...which ain't good).
There's also the ideal gas law PV=nRT which you were indirectly referring to in your post....it sort of applies to fuel vapors.... I don't think I'm really using this law correctly, BUT in a nutshell, it says you need to increase pressure (P - like you mentioned) or decrease temperature (T) or use a different blend of fuel (n).
Short answer to the original poster...…"it's not possible based on the laws of physics to make an anti-vapor lock additive"
67belvedere/225
Well-Known Member
on late 80"s jags the fuel line runs into the a/c line so it cools it down as it passes through
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Hey! I boiled water at room temperature in High School Science Club!
Put it in a vacuum chamber and voila!
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Doesn't the fuel injection system return the fuel to the tank?
PurpleBeeper
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Yeah, but the pressure is still much higher leading up to the engine. Now that I think of it, fuel injection might also act as a "vapor separator" too.
Does anybody know if the return line on an injected motor would return any "boiled fuel vapor" too back to the tank?
69a100
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Hey! I boiled water at room temperature in High School Science Club!
I've boiled water in a paper cup a few times!
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Yep. I boiled eggs in paper Dixie cups, filled with water and stuck straight in the campfire.
Ranger16
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I think it would, but only when the fuel pressure regulator valve is open, as in low fuel demand such as at idle (high vacuum).
PurpleBeeper
Well-Known Member
Makes sense....and that's when you'd be more likely to have a vapor lock issue I think. I mean, when fuel is flowing quickly, it doesn't have a lot of time to set next to something hot & boil.
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