hollombe@ttidcc.UUCP (Jerry Hollombe) (03/20/85)
>From: klein@ucbcad.UUCP >Newsgroups: net.auto,net.consumers >Subject: No Leaded Gas --- My Own Answer >Message-ID: <148@ucbcad.UUCP> >I would welcome ANYONE out there who is a real live Mechanical Engineer >and who really knows internal combustion engines to contribute to this. I'm not a Mechanical Engineer, but I am a licensed Airframe & Powerplant Mechanic. >I know that one thing I can't find anything about is unleaded gasoline >itself, since it seems it didn't exist when most of these books were >written. Does it burn at a higher temperature than leaded? One of the things I learned in mechanic school was that the power derived from a given amount of fuel in a piston engine is more closely related to compression ratio and ignition timing than to actual BTU per gallon. In fact, the difference in BTU/gal. between leaded regular gas and leaded high-octane (for example) is relatively unimportant in terms of power output. The additional power of engines burning high-octane gas comes mostly from the increased efficiency derived from the higher compression ratio and greater spark advance they can use without causing detonation (aka: ping, or knock). Combustion chamber temperature is controlled by compression ratio, spark advance, and fuel/air ratio. The question, therefore, is not whether unleaded gas contains more BTU/gal. than leaded, but whether it can sustain higher combustion chamber temperatures without detonating. This can be determined from its octane equivalence number which is really an indicator of resistance to detonation. -- -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_- The Polymath (aka: Jerry Hollombe) Citicorp TTI 3100 Ocean Park Blvd. Santa Monica, CA 90405 (213) 450-9111, ext. 2483 {philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe