– Why can V6 engines not just get “smaller” for fuel efficiency vs going Turbo V4?

Question

I guess what about having extra pistons makes mpg worse vs. 1.8L, 2.5L, 3.5L, etc.?

In: 168

Answer 1

Volumetric efficiency. In a naturally aspirated engine the amount of fuel air mixture entering the engine is determined by the diameter of the cylinder and stroke of the crank shaft. Combined with the compression ratio you can factor out what will be the most efficient. (Not most powerful) that is set, the only way to get more efficient is to reduce parasitic drag. Meaning less rotating mass.

Forced induction, like a turbo, can achieve higher compression ratios and with less cylinders comes less rotating mass. End result is the same power output in the target rpm range.