And at the end of an 18 hour day I'm bound to make mistakes.I've got plenty of experience as a professional mechanic,and have studdied what materials I could find on related sciences like metalurgy and thermodynamics.And like I said,from all I've seen and read I agree with the basic laws involved.But one indevidual here(not you Craig,You've been more then civil enough) basicly calls me an inexperienced fool because he disagrees with me.Wasted motion can't be changed much in currant engine designs.And thermal efficiency increases of any appreciable ammount are not cost effective.To the best of my knowledge the 98% efficiency in burning the fuel is after the catalytic converter.Not in the combustion chamber.I rode in his truck several times with one pint of fuel being gravity fed to the carburator.We went just over 20 miles each time in city driving.And you'r absoultly correct about wankel engines being more efficient due to fewer moving parts and less parasitic power loss.The outer edge of the rotor uses a spring loaded scraper which acts like a piston ring to maintain the fuel air mixture in each chamber section.The problem with the engines design though is the blowby which occurs past the ends of the rotor.If someone can devise a way to better seal the chambers,I believe the engine would then come into more wide spread use.The reason fuel injected engines get better fuel mileage then comercial carburator designs is due to the high pressures in the injection system.The fuel enters the combustion chamber as a very fine mist,which burns more readily then the droplets common in a carburated engine.A direct injection engine(gas or diesel) is even more efficient because the mist goes directly into the combustion chamber and has almost no chance to clump into drops before being exposed to spark or the heat due to compression igniteing the fuel.But the most effective combustion would be a vaporized fuel.I realize furnaces are both thermaly efficient as well as fuel efficient.Which an auto engine couldn't begine to compare to.But combustion efficiency could stand improving.But most who have tried have vaporized the fuel to much,and left tar residues behind that are even more damaging then normal carbon deposits.While I don't deny the basic laws of thermodynamics,I do question some theories of application.Please try to understand the different aspects that are involved when considering efficiency.Thermaly,I personally doubt a 4 stroke piston engine will ever be practicle at more then 45 or 50% efficiency.My point of the coolant temps in Smokey's design were lower waste heat output due to better heat utilisation.And I know his design was supposedly later proven not to work and instead self destructed.But this was after showing others previously,for many hours of opperation which the press witnessed,that his engine worked well.He never sold his engine willingly to Chrysler.And I tend to suspect the engine was tampered with causing a convenient catastrophy.Is that an unreasonable thing to suspect?And I don't know what the parasitic power loss percentage is in a piston engine.I doubt if it can ever be much improved either.But my point all along was combustion waste.The main reason for catalytic converters.And thanks Moneypit for reminding me leaner mixtures create higher oxides of nitrogen emmissions.Considered as the main cause of acid rain,this alone could be the reason lean burn technology is supressed.