Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
The S/C Engines internally are actually different to the ecotec engines. The Heads are different, the Compression Ratio is Lower. The Camshaft sprockets, Crankshaft, Piston & Rods, etc are all slightly different (Larger Pins, Larger Diameters, more oil holes etc) to cope with the extra boost for reliability.
The Injectors are also a Larger capacity (Same as V8) to spay more fuel when needed.
As for fuel consumption, im actually quite happy. I get around 14-14.5 Lt Per 100km with a pretty medium-heavy acceleration suburbian driving.
Definatly worth the extra consumption for the power gain. :thumbsup: