Date registered: Aug 2005
Vehicle: 1972 250C, Ducati ST
Location: Norfolk, Virginia
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: Adding Acetone to your Gas
If your engine's fuel system is clean, and the engine itself is in good shape and tuned properly, there's nothing you can use, additive-wise, that's going to give you anywhere near a 25-30% increase in fuel economy.
There's really not much fuel passing through the combustion chamber unburnt in the first place, so there's very little room for improvement. If you look at the results of a tailpipe emissions test, the numbers for unburnt hydrocarbons are usually less than a few hundred parts per million. To be fair though, you should really look at the results for a car that doesn't have a catalytic converter, since a converter will mask the effects of unburnt hydrocarbons in the engine.
If your carburetor or fuel injection system is really cruddy, and you have fluffy carbon deposits in your combustion chamber, I could believe that additives could give you an improvement from cleaning the fuel system, but you'll never see big improvements in an engine that's already operating as designed.
The article that the original poster linked to claims that unburnt hydrocarbons are caused by the surface tension of the fuel molecules raising the vaporization temperature of the fuel, using the example that water can remain liquid up to 300F because of surface tension, instead of boiling at 212F. This happens because the "vapor pressure" of the water cannot overcome the surface tension at the "normal" boiling point. That's fine, but it's really a bad example when it comes to fuel, because a) The vapor pressure of fuel is a LOT higher than the vapor pressure of water, b) the surface tension of gasoline is a lot lower than water, and c) the temperature in the combustion chamber is a LOT higher than 300F. All of these factors mean that it's going to be almost impossible for gasoline droplets to stay in a liquid state throughout the combustion process.
When hydrocarbons *do* leave the combustion chamber unburned, it's usually because there wasn't enough oxygen in the mixture to fully burn all of the fuel (in other words, the air/fuel mixture was too rich in the first place).
In short, I'm not convinced that there's a significant amount of fuel leaving the combustion chamber unburned in the first place, unless there's excessive wear in your engine or some problem with your ignition system or fuel system. That's why all the gimmicks like vortex-inducing vanes in the air intake, magnets on the fuel line, and devices that inject platinum particles into the air/fuel mixture have been proven ineffective time and time again.