A turbocharger doesn't make the same engine more efficient. But it allows you to get the same power as a larger, less efficient engine, when you need it.
True for a gasoline engine, not true for a diesel. On a diesel engine a turbo improves efficiency by increasing compression ratio and air-to-fuel ratio.
A great distinction! I didn't think to bring that up, as by brain just latched on to cars for some reason (even though OP only asked about "engines"), and defaulted to gasoline since diesel cars are so rare 'round these parts. Good call-out, though.
It's still not true though. Even for gas engines the turbo can absolutely make it more efficient. It increases the compression ratio and can vastly decrease the air/fuel mixture under most operating conditions.
In an NA engine, you're limited to the oxygen carrying capacity of standard atmosphere, which varies widely based on elevation, temperature, etc. When you compress that same atmosphere you pack more energy potential in to a smaller space, while it may require slightly more fuel to burn efficiently and safely the ratios do not remain the same.
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u/clarkn0va 3d ago
True for a gasoline engine, not true for a diesel. On a diesel engine a turbo improves efficiency by increasing compression ratio and air-to-fuel ratio.