– 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

Short version: it would be inconvenient for little gain.

While we can get into a lot of details about power curves and such the ELI5 super-simplified version is: smaller displacement, less power. Not cylinder count, displacement.

So a smaller V6 introduces a number of manufacturing complications, more moving parts, etc… compared to an I4 of similar displacement or slightly smaller with forced induction (the turbo) to make up the lack. The extra moving parts in a v6, minimum cylinder wall thickness, etc… also take up space you might prefer to spend on displacement so at a certain point you get more displacement in the same overall space with fewer cylinders.

V6s are worth it when you want to get into a certain displacement within a certain form factor but if you’re downsizing that overall size then an I4, even turbo charged, can get similar results more easily from a consumer point of view.