- Thread starter
The big radials did not offer the performance at altitude over the Allison that the take-off power figures suggest. Not without using cowlings and exhaust set ups that were not used historically until later in the war.
Using a late 30s (P-36) state of the art cowling the P-36 had either a 22% increase in drag over the P-40 or a 22% loss due to drag and poorer exhaust thrust.
Take 22% away from the R-2600 A series at 12,000ft and you wind up with just a bit less power than the Allison -39 engine.
The R-2800 A series does a bit better (and is smaller in diameter) but is over 350lbs heavier than the Wright engine. Which is almost 600lbs heavier than than Allison (of course the Allison needs nearly 300lbs worth of radiator and coolant).
R-2800A, in 1-stage variation, was supposed to do 1500 HP at 14000 ft on military power. That is 40+% better than any in-service V-1710 before late 1942 - quite an advantage.