I would have thought that since an SC uses some engine power to drive it that economy would come down. I also thought that TC should give power without sucking much from the engine as it's driven off the exhaust? That is awesome economy from a V8, my Buick only gets 11lph. You probably have the six speed, yeah? That would make a difference I'd think.
Yeah, 6 speed manual.
It does use engine power, but the charger and the engine are barely working at those revs, I'd have to find the sheet, but its something like 500nm at 1600rpm at the wheels (sheet shows about 600nm at 1800rpm), thus the no effort to cruise along. The standard SS with the 6.0 and manual sits around the 10l/100 mark for comparison.
When driven normally the S/C 6L is more like 14-16L/100 though, because the whine and exhaust is too nice not to make the neighbourhood hear it.
Like everything, there will be losses somewhere, to get the turbo effective its when its actually spinning and creating boost pressure otherwise it is something else in the way as such.
Just size it all right and youll do well. I think the power will be enough for your enjoyment, although the more you drive it, the more you get familiar with it and the less you notice its potent.