Internal voltage regulator

Stock regulators are not supposed to run at constant voltage; they should adjust with temperature. Batteries can handle a little more volts when cold. The race regulator may be locked at constant voltage to assume either a trunk mounted battery or that the car is never driven long enough to fully charge the battery.

However, after cutting open a modern Chinese made stock replacement voltage regulator, I found they'd omitted the temperature compensation circuit to save 20 cents or so per part ...