Re: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded

Posted by Bill Jones on January 03, 2002 at 21:29:30 from (63.17.133.106):

In Reply to: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded posted by BushogPapa on January 03, 2002 at 19:16:36:

Well,I don't know where your info came from but...In 1921 it was discovered that a very small amount of of a poisonous organic compound,tetraetyhl lead (Pb(C2H5)4) added to the fuel ,would dramatically improve the antidetonation characteristics .TEL was a standard and important additive in both automotive and aviation engines.Only in the last few decades has there been a concerted effort to eliminate leaded fuels because of enviromental considerations. Beginning in the 1960's,Turbine engines started to replace reciprocating engines in millitary and airline aircraft ,and the need for aviation gasoline decreased tremendously.General aviation does not create enough demand to make aviation gasoline an economical product for retailers.For many years automobile gasoline was considered to be totally unsuited for use in aircraft engines,but it was used illegally in a number of instances.The FAA Definitely disapproved of the use of automobile gasses,and the engine manufacturers made it very clear that its use would void any engine warranty.Most small engines were designed for Grade 80 fuel with its0.5 milliliters per gallon of TEL,then when grade 80 became unavailable,operators of these enginesfound that the 2.0 ml/gal of the100LL(100 octane-low lead)was too much,and there was a rash of serious problems with lead fouled spark plugs and sticking valves.even the addition of Tricresyl phosphate(TCP)(used as additive to eliminate fouling of spark plugs,a very common ocuuramce with leaded gasoline) to help scavenge the lead deposits did not completely solve the problem.The shortage of available grade 80 fuel with its high price and scarceity forced many owners to quit flying or switch to a less costly fuel,and automobile gas was the logical choice.The Experimental Aircraft Association(EAA) made an extensive and in-depth study of the use of auto gas ,and as of the mid 90's the FAA has approved its use by the issuance of a Supplemental Type Certificate (STC) for engines designed to run on grade 80 gasoline.More than 12 years of research into the use of automobile gas in airplane engines designed for grade 80 avgas has shown that auto gas can be as safe as ,and more economical than operating on 100LL aviation gasoline.Currently avgas manufacturers and aviation engine manufacturers are working to produce an acceptable NONLEADED fuel for aircraft usage.Due to the small demand ,and the increasing enviromental concerns regarding lead,it is only a matter of time before all leaded fuel is removed from the market.By the way MANY aviation engines operate at greater than 2,300 RPM,a modern Lycoming O-235 ,a common engine, is rated at 2,550 RPM.I have seen the lead fouling in big radial and 12 cylinder Allison aircraft engines it is NOT what lubes the valves,The little amount of lubricity it offers is offset by the plug fouling and cylinder bore coating which needs to be removed periodically.Are you involved in aviation? TEL had its place,but that technology has been retired,not sure about the warbirds who need leaded fuel for their powerplants,although gasoline has improved 10 fold over the 40's fuel so it may not be a big problem.Sorry this is so long BillJ

Follow Ups:

• Re: Re: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded BushogPapa 07:21:25 01/04/02 (1)
  • Re: Re: Re: Re: Re: Old engines (pre 1970) and gasoline, leaded - unleaded Bill Jones 08:27:13 01/04/02 (0)

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