Back in the olden' days we used 115/145 avgas in actual aeroplanes. The
115 part is the octane number in "normal" mixture and the 145 was the
rating for "rich" mixture. The engine was an R1820 that had been
developed from about 575 hp to about 1500 hp by turbocharging and
serious advances in metallurgy- max boost was 56" Hg at military power.
The higher octane ratings were due to additives, primarily lead.
Again, in the olden' days, use of avgas was considered not economical
for racing or street use because of the cost which was more than pump
gas and there was no performance advantage. Avgas works best for
extremely high compression ratios or boost.
Cheers,
Dave Mericle
Leucadia, CA BEACH-N-RIDES
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