On Tuesday, October 16, 2018 at 3:14:01 PM UTC-5, Charlie M. (UH & 002 owner/pilot) wrote:
To sorta answer this, there is an ongoing push by AOPA and other groups along with the FAA (in the US) for a suitable unleaded fuel for use in the older "leaded fuel" engines.
I know we added a supplement to our low lead fuel for our towplanes. Don't remember the name of it.

As to using auto derived engines for aircraft duty, sheesh, other than endurance racing (likely max runtime until rebuild, maybe 25hrs?), auto engines were not designed to run near full power for about 2000hrs before rebuild.
While most piston aircraft engine are rather archaic compared to modern auto engines, they are rather dirt simple and last for a long time at high power loads.
Yes, a better ignition system can help, although try getting that certified.
Yes, in the US, and other countries, there is a push to find a suitable unleaded fuel.
Aviation is still a small niche market (a bit larger than sailplanes, but still small for Shell, BP, Exxon, etc.), so what do they care about losing us due to environmental concerns?

There have been discussions on Subaru forums about peeps wanting 300hp+ from a 2.5L NA Subaru engine for aero use.
Yes, can be done, but at what cost?
Most is in the experimental arena.

As to going LPG, it usually is a big drop in power due to the lower power density of the fuel compared to gasoline, leaded or unleaded.

Really hard to beat gasoline for now. Anywhere close is big money to get there.

Hey, I am all for innovation, yes, we need to move from leaded fuel, but there are tradeoffs.
Just ask the peeps that get ethanol blends for cars based on season. There is a MPG drop because of it. The little performance gain due to ethanol cooling is more than offset (thus far) by the lower power density of the fuel.
This is more common in northern bits of the US, especially in metro areas (I am in the NY metro area).
I log my fuel mileage, I can tell when fuel stations go from summer blend to winter blend. It averages 15% drop in mileage.

Wrong again, Charlie.
In the era of smallish 50-100HP auto engines in Germany in the 70's we used to flog them for many hours at full throttle on the Autobahn. They were made for this abuse and lasted just as long as those in a taxi.
Herb