Scavenging just... the fumes?

[Photonfanatic]

So I was listening to Art Bell, (go ahead and say it, that's where it all went wrong) and there was this guy on there talking about how he had somehow converted his car to only scavenge the fumes of the gasoline. Seeing as how gasoline itself, as a liquid, isn't flammable. Its the fumes that ignite. So he would siphon off the vapor and inject that into the cylinder, thus saving a lot of fuel. Then I ran into another guy on another forum that said he did it with his pontiac fiero, where he heated the gasoline to get it to make enough fumes. Sounds dangerous.

Is there any viability to all this? It seems like you would get a lot more range out of your fuel if you could just get the fumes.

[ChazInMT]

I could be mistaken, but your engine burns like 95% + of the fuel that goes into the cylinder. Really not much room for improvement in that part of the equation. People try to baffle with B$ when they claim that engines are only 30% efficient....well they are, but that doesn't have to do with the fuel burning, it is the pumping, thermal, and friction loses that cause that. But they make you think it's only 30% of the fuel being burned so if you improve combustion you'll see an improvement in MPG's, Power, cleaner emmissions, and your love life.

I conclude with:

[Ragnarok Warrior]

The guy who said he was siphoning fumes is more than likely talking complete "nutritionally drained biological output" (from a bull no less). However the second guy was partially correct.

The Fiero was built by Smokey Yunick, who designed the hot vapor engine. The engine ran on a "turbocharger" for gasoline vapors heated by the exhaust. It truly did work and the gas mileage figures were pretty good. Although he was able to get twice the horsepower from the engine, it wasn't just from the hot fuel vapor. Because the vapor was fuel in an "excited" state, this allowed MUCH higher compression (like LNG and LP engines) and timing advance, which in turn increased the efficiency of the engine and the increase in horsepower.

The major drawback to the hot vapor engine was it's NOx emissions, which were at least four times higher then with a gasoline engine because of the heat involved.