On Mon, 7 Nov 1994, David Carment wrote: > OK dumb question why don't we run diesel in our engines? If its is more > efficient and cleaner then we should all do the diesel thing. (it is used > to be a whole lot cheaper too). Or is gas somehow designed to be an > optimal fuel for other (more conspiratorial) reasons.... -- No conspiracy. First off, diesel is definitely NOT cleaner, as any of the tailgaters in the recent thread can tell you. In addition, while BTU/lb is very important, a factor called "flash point" is also vital. Alcohols, despite (or perhaps because of) their lower BTU value evaporate and burn at even lower temps/pressures than gasoline. Diesel fuel doesn't. Your standard gas engine is actually a high precision instrument that mixes fuel, air, and spark in very precise amounts at very precise times. The standard vacuum on a carb won't even pull diesel, it's too thick. While a fuel injector might force it into a cylinder, it won't evaporate fast enough to be a good fuel/air mix when the spark goes off. So, no go on running diesel fuel thru your gas engine (except as a cleaner and even then it looks like you forgot to install your piston rings because the fuel/air mix is AFU). The high compression in a diesel engine not only raises the temp in the cylinder high enough to ignite the diesel/air mix, it raises the temp high enough (previous to the ignition point) to evaporate the (relatively thick) diesel fuel in the combustion air. Anyone who wants the gorey details, I can supply them, but in essence: Gas works best in cars designed for gas. (use the lowest octane rated gas you can, as all gasoline has the same BTU/lb) but oxygenated fuels {w/ethanol/MBTE/etc.} *may* reduce the amount of pollutants your car spews Diesel works only for diesel (or cleaning your engine) The full bore/no pollution/low cost/high mileage solution is to convert your engine to LPG (run your engine off your reefer), but initial cost/fuel availability is a real problem. LPG has a high BTU/lb ratio, burns very cleanly, and you can generally avoid the road taxes on automotive fuels. On the other hand, conversion can cost 1-2 thousand US$, and fueling at 3AM is a real problem (try to find an open camp ground/hardware store, in January, in Canada). H Steven Dolan dworkin@netcom.com
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