[{HVY-E}Jinxx]

The Allison that powers the P-40 was a supercharged powerplant though it did not have a multistage supercharger.

Sorry sir, but you are incorrect.

The P40 was not supercharged. The British experimented with superchargers in the P-40F model, but it was not powered by the Allison. It was a Merlin powered machine.

As noted in Aviation History's Website.....

"The P-40 was initially designed around the Allison V-1710 liquid-cooled inline engine which offered better streamlining, more power per unit of frontal area, and better specific fuel consumption than did air-cooled radials of comparable power. Unfortunately, the rated altitude of the Allison engine was only some 12,000 feet, rendering combat above 15,000 feet a completely impracticable proposition. The P-40's ancestry dated back as far as 1924; the famed Curtiss Hawk fighters being in the forefront of all US warplanes. But its development was hindered from the start. The overall limitations of its design were such that the addition of multi-speed superchargers was considered inadvisable in view of the pending production of superior fighter designs."

The only P40, (Allison Powered), to have an integral Supercharger was the Prototype.

"One of the most significant steps in P-40 development came in 1941, when a British-built Rolls-Royce Merlin 28 engine with a single-stage, two-speed supercharger was installed in a Kittyhawk I airframe to improve its high-altitude performance. The Curtiss H-87-D, or XP-40F, as the Merlin-powered prototype became known, then had 1,300 hp available for takeoff, and 1,120 hp at 18,500 feet, which offered vast improvements over earlier models and endowed a maximum speed of 373 mph. This was reduced slightly in the YP-40F, which, like later variants, had the Packard-built Merlin V-1650-1 and revised cooling, the air intake above the cowling being incorporated in the radiator scoop. Gross weight climbed to 9,870 lb.

Following experiments in cooling-drag reduction in 1943 with a P-40K-10-CU which had its "beard" radiator removed to wing installations, and in rear vision improvements by installing a "bubble" canopy on a standard P-40L, a general " clean-up " programme was initiated, resulting in the sole XP-40Q. With a 1,425 hp Allison V-1710-121 engine, the XP-40Q was modified from the first P-40K-I to have a "bubble" canopy and cut-down rear fuselage, wing radiators and, eventually, clipped wing tips. A four-blade propeller was fitted, and water injection installed. With a weight of only 9,000 lb, the XP40Q attained a maximum speed of 422 mph. This was still less than the speed attained by contemporary production Mustangs and Thunderbolts , however, and the XP-40Q did not achieve production. "

S!