The f4u 4 is the last variant to see action during world war ii deliveries to the u s navy of the f4u 4 began late in 1944 it fully equipped naval squadrons four months before the end of hostilities it had the 2 100 hp engine when the cylinders were injected with the wateralcohol mixture power was boosted to 2 450 hp 1 830 kw the propeller was changed to a four blade type maximum speed was increased to 448 miles per hour 721 kmh and climb rate to over 1 180 mmin as opposed to