gnome@olivee.UUCP (Gary Traveis) (09/13/85)
(*) I'm trying to find a source of information on the chemical make-up of standard auto gasoline. What is it's general composition? What other mixtures burn the same, except without the crap that causes varnish build-up in the carb? What can be used as a substitute? How about LP and Propane conversion? (what can happen to high rev engines running them?) Gary (hplabs,ihnp4,allegra)oliveb!olivee!gnome
clewis@mnetor.UUCP (Chris Lewis) (09/16/85)
In article <479@olivee.UUCP> gnome@olivee.UUCP (Gary Traveis) writes: >(*) > >I'm trying to find a source of information on the chemical >make-up of standard auto gasoline. > >What is it's general composition? Gasoline is hardly a "pure" substance. Fresh out of a fractionating tower it contains traces of almost all of the hydrocarbons there were in the original crude. However, they try to avoid the shorter ones (say CH4 up to C5H12) and the longer ones (say C10H22 and upwards). The former because it makes the fuel too volatile (dangerous - though you do need some volatility to be able to start), and the latter because it makes the fuel too "sticky" (not-quite-burned hydrocarbons causing various engine deposits). Plus, all of the various hydrocarbons exist in all of their isomers too. Octane ratings compare a gasoline "average" mixture with pure C8H18. It's too expensive to create a "pure" gasoline. I used to work in a refinery lab. We had to perform distillations on the stuff to determine boiling curves, these curves were used to determine the "base" grade of the gasoline. You'd be amazed at what goes into gasoline. "Light gas" (mixed with "heavy gas" in various concentrations to make different grades) was so volatile that it would boil off in your hand. There are also various traces of things like mercaptans (eg: H2S), and in leaded gas, tetra-ethyl lead. >What other mixtures burn the same, except without the crap >that causes varnish build-up in the carb? Probably any "sharp-cutoff" gas (eg: only Octane and nothing else). >What can be used as a substitute? Just about any "light" pure burnable: Propane Natural Gas (mostly Methane) Alcohol/Gas mixtures (Gasohol) Hydrogen Butane (though it might freeze in low temperatures) Alcohol Alcohol and Nitromethane (racing cars and model airplane engines) Benzene/Heptane/Septane/ whatever (some of these are quite dangerous (eg: Benzene is a carcinogen)) Propane is quite popular, LNG, Gasohol and Hydrogen stations do exist, but are relatively rare. The others are probably too expensive for ordinary driving. All a substitute fuel needs is: - a relatively high vapor pressure so that a flammable mixture gets to the spark plugs, - a relatively non-poisonous exhaust - relatively cheap. > How about LP and Propane conversion? What about 'em? Other than the fuel tank and replacement of the fuel injector system they are pretty much the same. Obviously the engine needs retuning. > (what can happen to high rev engines running them?) Probably nothing as long as the oil distribution system is adequate. Ordinary gasolines provide a small amount of lubrication on their own (because of the bigger hydrocarbons), so the oil distribution system is probably slightly more critical. -- Chris Lewis, UUCP: {allegra, linus, ihnp4}!utzoo!mnetor!clewis BELL: (416)-475-8980 ext. 321
dave@cylixd.UUCP (Dave Kirby) (09/19/85)
In article <479@olivee.UUCP> gnome@olivee.UUCP (Gary Traveis) writes: (among other things...) > How about LP and Propane conversion? A few years ago I had my truck converted to Propane. It was a '71 Ford with a 390 V8 engine. I had it converted just after the last of the gasoline crises, in 1980. The conversion cost about $800, cheaper if you got the smaller tank. I got an 80-gallon and paid the extra. What they do is mount the tank in your pickup bed or trunk and run a well-guarded hose into a special adapter that fits between your carburetor and air filter. This adapter also has hoses that connect into your heater, so that the liquid propane coming into the adapter is warmed and vaporised. There is also a gadget that cuts off the propane when there is no engine vacuum, and another one that cuts it off when there is no ignition. Also, they put a switch on the dashboard that switches between gasoline and propane. How did it work? Beautifully! I tried the truck out with propane and swore I'd never go back to gasoline regularly. Propane, you see, is equivalent to gasoline with an octane of 110, and the truck just loved it. The engine was in poor shape, leaking oil and the like, and would not run well under gasoline. But it never had a moment's starting or running problem with propane, even in the dead cold of winter. At the time, propane was 70 cents a gallon, giving me better fuel bills even though the truck got less mileage per gallon with propane (11 MPG as compared with 15 MPG with gas on the road). And you can go FAR on 80 gallons! I think perhaps one reason the truck showed worse gas mileage was that with propane I never bothered to tune it. It was probably running on 6 of the 8 cylinders. With propane it didn't matter. The stuff was pure vapour going into the intake manifold, so it was easy for the engine to digest. Almost pure water vapour came out of the exhaust, so I saved muffler repair bills as well (propane burns MUCH more cleanly than gasoline). Now the problems. First, propane didn't have the gunkiness of gasoline, so it didn't plug up the cracks and crevices in my old engine as well; thus, oil usage increased slightly. Second, if the water in the radiator got a little low, then it would not get pumped into the adapter to warm the propane. The result was that I would start out one cool morning only to have the engine start sputtering after about 2 minutes of driving. Finally it would stop all together and I would raise the hood to find the engine block and adapter frozen in ice. Not really a problem, though; I just let it thaw out, added more water to the radiator like I should have done in the first place, and the thing took off like a champ as usual. Then there was the problem of going back to gasoline after having driven the thing with propane for several months. I pulled over to the side of the road, switched the truck from propane to gas, and cranked the engine to get gas into the carburetor bowl. The engine finally caught on, but after a few seconds it sputtered and stopped, and would not start. I raised the hood, and found the whole engine baptized in gasoline. What had happened was that the needle valve had frozen open from not having gasoline running through it for a while, and ... well, you can guess the rest. The folks at the propane place advised that I run the truck on gasoline at least one day a week to keep that needle valve slick and happy. Then, alas, the final straw. I moved from Mississippi, which had very little road tax on propane, to Tennessee, which had an outrageous road tax. It put propane's price up to the point where propane was more expensive per gallon than gasoline. I still ran the truck on propane, because it ran better and was more convenient with that 80 gallon tank (Boy, I miss that tank!); but I sure felt ripped off. I figured it out one day and found that it would be worth my while to drive the 50 or so miles down to Mississippi to get my propane, where I could get it cheaper. That's what I know about propane. I have since sold the truck, but if another gas crisis hits I'll take my 1975 Behemoth Electra 225 down to that little place in Byhalia, Mississippi and get it put on propane. The stuff is great! ----------------------------------------------------------------- Dave Kirby ( ...!ihnp4!akgub!cylixd!dave) (The views expressed herein do not necessarily reflect those of RCA Cylix. They may not even reflect my own.)
maloney@uiucuxc.Uiuc.ARPA (09/20/85)
Rember that the engine was designed to operate at a particular combustion temperature. Any other chemical combination that does not come within a small range of this temperature will possibly cause engine trouble. If the mixture burns to hot, one may find cracks developing in the engine due to the metal expansion and/or increase in brittleness of the metal (metal changes its atomic arrangements when heated). Also, a decrease in engine life may result. Check all the potential problems carefully before switching to another fuel.