Bob Matthews wrote:

Scott M. Kozel wrote:

That is partially true. Packard modified the turbocharger to produce
more high-altitude power,

The main improvement that Packard incorporated into the Merlin was
adopting the Wright supercharger drive quill. This modification was
designated the V-1650-3 and became known as the "high altitude" Merlin
destined for the P-51. The ability of the supercharger to maintain a
sea level atmosphere in the induction system to the cylinders allowed
the Packard Merlin to develop 1,200 horsepower at 26,000 feet.

When you say "turbocharger," are you referring to an exhaust gas driven
compressor? Or mechanically driven?

Sorry, I miswrote. It was mechanically driven by the engine, a two-
speed two-stage supercharger.