I know I have been all over the map with blog postings recently. Mostly it is because I don't want to give away what I am working on untill Sturgis! In the mean time, here is a good one. In my obsession with aircraft engines and all their various configurations, I came across this. It is called a Turbo Compound. This was yet another WWII era concept for boosting piston engine performance, similar to a supercharger or turbocharger. In this case, spent exhaust gasses are routed around the crankshaft of the engine. The idea is that the fast-moving gasses actually help turn the crank itself, rather than an air compressor to re-feed the intake. A main reason why this was explored as an option was because, unlike conventional forced induction, it does not increase fuel consumption, but still increases power. These systems are also known as "blowdown turbines", because they take specific advantage of the fast-moving exhaust gasses created by the piston moving down on its power stroke. This is possible by having the exhaust valve open before bottom dead center on that stroke, allowing explosive combustion gas to escape early. Get it? Give a little here and gain a little there. Amazing. Obviously I am wondering if this would be a viable way to increase power on a motorcycle. Apparently these engines (at least in aircraft form) were not vary popular, as the advent of turboprops and jet engines took over. However, detroit diesel apparently made an engine with one in 2001. ok, here are some pics: This one is in a radial aircraft engine.
Apparently a few found their way into the later versions of the Lockheed constellation. Howard Hughes was partially responsible for this aircrafts development. (as seen in the movie "The Aviator")
Apparently, turbo compounds were hated by mechanics because the exhaust valves got the shit beat out of them and needed frequent replacement. It does make sense, if the valve is opening early on the power stroke to increase exhaust manifold pressure, it is going to get a lot hotter. Maybe it isn't such a good idea to try to adapt this one to bike. It is hard enough to keep a regular Harley running right!