Comments by "crazypj" (@1crazypj) on "Forbidden Technologies and The Silencing of Their Inventors" video.

@wazza33racer Actually, seems like only 3 Allison compound engines were ever made. Allison original HP rating was only 750, which eventually rose to 1425 which is why Rolls-Royce Merlin's were used in P-51 (more accurately, high altitude performance with two speed supercharger) The Wright R3350 was the successful compound engine. The major limitation in any four stroke internal combustion engine is keeping the exhaust valve cool enough to prevent pre-ignition. Aircraft piston engines only turn at about 2,500 to 3,000 rpm unless drive is taken off camshaft running at half crank speed or some other reduction gearing. Propeller tip speed had to be kept sub-sonic. Another reason for jet turbines, etc, the Time Between Overhaul is much much longer than with piston engines. The Allison V-1710-E22 (or 127) compound engine isn't mentioned in any normal literature but can be found quite easily using title you supplied The Renault 1500 cc F1 motor was making over 1200 bhp in qualifying motors, lifespan was pretty short and they only got about 1.5 mpg
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