quote: You forget one aspect of a Blown engine (especially Turbocharged). The increase in Volumetric Efficiency, a boosted engine can have better than 100% Volumetric Efficiency, while an N.A. engine is rarely over 60-70%. Which means that the that the Turbocharged 2.0 @ 14.7 psi, will less air and fuel than an N.A. 4.0L engine. Further a Turbocharger actually converts some of the energy that would otherwise be lost out the tailpipe in the form of heat, Also the turbo'ed engine will have better scavenging than a N.A. engine.
quote: Not exactly. If were to follow your example, and have a 2.0L turbo vs a 4.0L NA engine, with both engines having identical power curves, and drove them exactly the same, the turbo will come out with higher mpg. Granted, it would be a small difference, but it would still be there. The Turbo engine is almost always going to be lighter than the NA engine. Less mass requires less fuel to move it.
quote: On top of this, turbo engines are tuned to run rich. They must run rich to avoid detonation on pump gas, and this increases their fuel consumption.
quote: Volumetric efficiency is simply a fancy way of saying "air intake" - I didn't forget any aspect, you're just using the technical term to rephrase what I originally said.
quote: Engines with higher volumetric efficiency will generally be able to run at higher speeds (commonly measured in RPM) and produce more overall power due to less parasitic power loss moving air in and out of the engine.