<VV> octane and alky

[Padgett]

>  However, I doubt if it can change the compression ratio
>of the engine to take advantage of ethanol's high octane rating (about 99
>(R+M)/2 basis).

GM is also moving toward true "fly by wire" with no direct connection 
between the gas pedal and the throttle plate. With that you can control 
chamber pressure via manifold vaccuum so you design the engine for the 
highest octane fuel and then dial back the effective compression ratio  to 
the current fuel. This is even easier to do with a boosted engine and a 
waste gate. (IMNSHO there is a place for supercharging - above 20,000 feet.)

This is really a far superior method than retarding the spark on detonation 
but was what the automakers had available that was cheap since with 
traditional controls they could not control the nut behind the wheel.

With electronic control, when the pedal hits the metal the computer can 
control the max chamber pressure to what the fuel is capable of. Toss in 
VVT and the engine can be kept at the peak of efficiency even on moonshine.

Padgett