In late 1941, Nakajima introduced the Sakae 21, which used a two speed supercharger for better altitude performance, and increased power to 1,130 hp (840 kW). Plans were made to introduce the new engine into the Zero as soon as possible.The new Sakae was slightly heavier and somewhat longer due to the larger supercharger, which moved the center of gravity too far forward on the existing airframe. To correct for this the engine mountings were cut down by 8 inches (200 mm), moving the engine back towards the cockpit. This had the side effect of reducing the size of the main fuel tank (located to the rear of the engine) from 518 litres to 470 litres.
The only other major changes were to the wings, which were simplified by removing the Model 21's folding tips. This changed the appearance enough to prompt the US to designate it with a new code name, Hap. This name was short-lived, as a protest from USAAF commander General Henry "Hap" Arnold forced a change to Hamp. Soon after, it was realized that it was simply a new model of the Zeke. The wings also included larger ammunition boxes, allowing for 100 rounds for each of the 20 mm cannon.
The wing changes had much greater effects on performance than expected. The smaller size led to better roll, and their lower drag allowed the diving speed to be increased to 360 knots (670 km/h). On the downside, maneuverability was reduced, and range suffered due to both decreased lift and the smaller fuel tank. Pilots complained about both. The shorter range proved a significant limitation during the Solomons campaign of 1942.The first Model 32 deliveries began in April 1942, but it remained on the lines only for a short time, with a run of 343 being built.                                                                                                                                         -- Wikipedia