Turbocharging has become more prevalent in the automotive industry over the past few years as solution to strict EPA fuel economy regulations and a over all desire to get more from less. But, are they as economical as their similar sized non-turbo rivals? Not necessarily. If you take a 3.0 liter normally aspirated engine and compare it to the exact same engine with a turbo added, you may find the turbo engine is less efficient, but makes a lot more power.
How auto manufacturers make that work is that they use a smaller displacement engine with a turbocharger to replace a larger normally aspirated engine. Both engines produce roughly the same ultimate power, but the smaller turbo engine is more efficient than the larger non turbo engine. You can get 300 reliable HP out of a 2.3 liter turbo four cylinder where it might take a 3.5 liter V6 normally aspirated engine to get that kind of reliable HP. That’s a lot more weight and physical size to deal with.
The smaller turbo engine is lighter and physically smaller than the normally aspirated engine and the engine is lighter. The new car with the physically smaller engine can have a smaller engine compartment, so the car can be lighter still. Less weight to move around makes for a more efficient car overall.
The simplest answer is that a turbo helps you achieve full consumption of your fuel and not let it go waste. This in turns result in better economy, more power and lower emissions. The trick involved is delivering more amount of air and that too pressurized which results in an enhanced breathing capacity of the engine. Such an effect can not be achieved in naturally aspirated engine.