Dinan Supercharger Hp 4.4 vs. 4.6is

[2002Silver4.6is]

The Dinan supecharged 4.4 puts out 421 hp while the 4.6 version puts out 451. Stock the 4.4 has 282 (the supercharger is only for models thru 2003). So the 4.4 gains 139hp, a 49% gain over stock. The 4.6is has 340 hp stock and 451 hp supercharged, a 33% gain or 111 hp.

If the 4.6 had the same 49% gain it would be putting out 506 hp. Why the difference? Shouldn't they be able to get the same percentage gain out of the two engines? I wonder if they are running different sized pulleys so they have different amounts of pressure. Even if the gain was the same amount of hp (+139) as the 4.4 the 4.6 would be up to 479hp....

Anyone with a Dinan S3 ever ask about this??