<VV> octane requirements

[NicolCS at aol.com]

Padgett  asked: <snip> However I just have this itch that a 3.5" bore engine 
with  a 9:1 CR that requires today's premium fuel has something odd about it. 
May  not be 
obvious but is there and I'd like to know  why.<unsnip>
9:1 Corvair's have always required premium fuel.  Today's engines have  the 
benefit of many technical improvements, so they can run on 87 octane  fuel.  
Here are a few of the big ones:
 
Corvair heads run hotter (water cooled heads run about 240 vs Corvair's 275  
and up)
Modern heads have much better squish and mixture tumble
40+ years of cylinder head design development
FI creates a more uniform mixture (Fewer lean spots)
EGR suppresses knock
Knock sensors detect knock and retard spark before we would even hear  it
Fuel-trim maps are automatically updated and ignition maps are more  precise 
.. to name the big reasons why today's 9:1 engines will run on 87  octane
 
I'm a big fan of modifying Corvair heads for .032" squish and at the same  
time boosting the compression to 9.25 or more.  No knocks (remember Nonox  
fuels?), and more power.
 
Craig Nicol