Great comments on the subject here - pardon the gross over simplifications please. I'll add what I know. "Octane" can be thought of as "Resistance To Pre-ignition" where the higher the octane number, the more resistant the fuel mixture is to ignition/burning. Lower octane fuel can have a tendency to pre-ignite via cylinder compression (compression on the upstroke raises cylinder temperatures to the point of combustion) rather than ignite when the spark plug fires. This is whats called "knocking" as in the benign case it cause the engine to make a knocky-rattling sound ( not unlike a diesel which in fact relies on compression ignition as a feature of its design ). In the bad case, pre-ignition can cause catastrophic engine damage where engines "grenade" themselves.
More or less, if you want to build a light weight/high power engine you want a higher compression ratio. As the piston travels upward on the compression stroke higher pressures are achieved and this allows designers to take advantage of different crank/cylinder characteristics to make more power in a smaller, lighter package.
We used lead in car gas because engine timing technology and fuel delivery technology were analog/mechanical and really very limited in terms of tuning potential. The cheap hack was just to use a fuel that was more resistant to burning in the first place. Just add a hotter spark/ignition system and it was good to go design wise. Given the old tech running in most GA planes, this was a natural thing to do at the time and the problem was well understood. To point here, modern non-lead additives have been around for a long time and the problem can be adequately solved with a non-lead substitute.
If you wanna get deep with this, take your old normally aspirated car and bolt a turbo on it!
More or less, if you want to build a light weight/high power engine you want a higher compression ratio. As the piston travels upward on the compression stroke higher pressures are achieved and this allows designers to take advantage of different crank/cylinder characteristics to make more power in a smaller, lighter package.
We used lead in car gas because engine timing technology and fuel delivery technology were analog/mechanical and really very limited in terms of tuning potential. The cheap hack was just to use a fuel that was more resistant to burning in the first place. Just add a hotter spark/ignition system and it was good to go design wise. Given the old tech running in most GA planes, this was a natural thing to do at the time and the problem was well understood. To point here, modern non-lead additives have been around for a long time and the problem can be adequately solved with a non-lead substitute.
If you wanna get deep with this, take your old normally aspirated car and bolt a turbo on it!