Surprised FI is wrong on this one....

Any engine needs two things to become closer to 100% Volumetric Efficiency (VE). More oxygen, and more fuel. Denser (cooler) air has more oxygen molecules in it per cubic inch than hotter air.

With a turbo car, it makes slightly less difference, as the turbo heats the air as it compresses it, but, when you start off with more oxygen per CI, you finish that way too. That produces a hotter flame in the combustion chamber, which acts on the piston/rod/crank with more force. That produces more HP.

We're talking maybe 1-2 HP in a standard passenger car with no intercooler.