About all these "new technology" alternatives...

I've notice that the alternative engine proponents often state that automotive engines are great because they have benefited from years and years of R&D, leading to fuel injection, overhead cams, electronic ignition, small bore/high rpm, etc. This makes sense, but here is my question: The Lyc's have been around for 30+ yrs too, what improvements have been made to them and why, if auto engines so much better, don't they look more like their automotive cousins?

What has changed in the Lyc's over the years? All I know of are roller tappets.

You've answered your own question

As far as a design is concerned they are as close to being optimum for the job at hand as you can get.

Materials have improved but when Honda went out to design a new airplane piston engine from the ground up they came up with...wait for it...A Lycoming clone!

Quite simply car engines are designed for a totally different application and they loose a lot in the translation..

More weight, more cooling drag, less fuel efficient, MANY more parts to break, systems to go wrong.

I am not targetting any particular conversion here but that is that starting point of issues to be overcome.

This is from a guy who had a car engine in his previous airplane.

there is a lot to be learned in translating individual systems maybe...e.e knock sensors, EI, FI etc etc...But the overall design of a Lyc is pretty much spot on.

Frank

You might find a few minor tweaks here and there - but the pain and heartburn of getting those tweaks through certification and into production far outweighs any benefit or market advantage they would confer upon the company pushing them. Bottomline, there's not much to improve upon that's worth doing. You'll have to get into an entirely different type of engine (turbodiesel) to come up with a truly "different" aircraft engine that fits the requirements well.