A lot of fancy good aircraft engines for sure. What Viking brings to the table is what now is very popular in a lot of new cars. Small / light / direct injected / turbocharged / all liquid cooled / not complicated / no exhaust pipes / inexpensive / affordable and plentiful worldwide OEM parts supply / any car mechanic can work on / no specialized internal engine components, type of engine. If you are serious about looking for real progress in engine development, watch the Honda video below. It shows all the reasons why the modern engines can do what they can do, and last a long time. Direct oil and fuel cooling of pistons, direct liquid cooling of the exhaust manifold, direct cooling of the turbo charger, precise and automatic control of turbo boost, not a single exhaust pipe other than the turbo down pipe, variable valve timing, sodium filled valves, high compression yet virtually detonation proof, car gas or 100LL tested for over 2 years, smooth starting and shutdown, 650-750 lb of thrust. Available as a 1.5L lightweight GDI or 2.0L for even more power. Replacement engines (if you were to damage yours) for $2,000, etc. For the best possible aircraft engine, if you are going for high technology anyhow, get one that is direct injected for additional power, better starting and detonation immunity. GDI has no disadvantages in an aircraft engine. Power is at lower mixtures and some issues with early implementation of GDI in cars do not apply to power hungry aircraft engines. Variable valve timing is important. There is a big difference between full power takeoff / climb and efficient cruise. Why would you not want max possible power yet optimized torque for cruise. Tere is so much more to consider than the "traditional" questions: 1)External oil lines / fittings: This is important. You might even count how many external (outside the engine block) hoses / connections your engine choice has. Then consider that while you are flying in the back country, every single one has a possibility of a leak and that even one leak could empty the oil system within 2 minutes. 2) Inline or horizontal engine layout: Inline is superior in every way. Only one cylinder head makes for a lighter design, simpler wire loom, simple cooling system, simple exhaust system, even engine temperatures, simple maintenance and a compact engine. 3) Air Cooled, Liquid cooled, oil cooled or a combination -
more to follow.