<VV> octane requirements

[JVHRoberts at aol.com]

Moving the spark plug closer to the center wouldn't be a bad idea either. 
 
In a message dated 6/21/2005 2:15:16 P.M. Eastern Standard Time,  
NicolCS at aol.com writes:

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