Correct, it used the Sakae 21(sp) over the Sakae 12, I don't remember the horsepower difference in my head but it wasn't a significant increase. Theres also the difference between the two models of A6M3 as far as aerodynamics go.
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 20 cm (8 in), 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 L (137 US gal) to 470 L (120 US gal).
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 670 km/h (420 mph). 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.
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In order to correct the deficiencies of the Model 32, a new version with the Model 21's folding wings, new in-wing fuel tanks and attachments for a 330 L (90 US gal) drop tank under each wing were introduced. The internal fuel was thereby increased to 570 L (137 US gal) in this model, regaining all of the lost range.
As the airframe was reverted from the Model 32 and the engine remained the same, this version received the navy designation Model 22, while Mitsubishi called it the A6M3a. The new model started production in December, and 560 were eventually produced. This company constructed some examples for evaluation, armed with 30 mm Type 5 Cannon, under denomination of A6M3b (model 22b).
A few late-production A6M3 Model 22s had a wing similar to the later shortened, rounded tip wing fitted to the A6M5 Model 52. These were probably a transition model, at least one was photographed at Rabaul-East in Mid-1943.
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There ya go. ill try to find the link. i literally just took this from a saved word doc that i copied from the internet as a source. <S>
The Model 22 was basically a better model A6M2 Model 21 with an extra 10-20mph max speed while the Model 32 was crap.