Originally posted by Horse:
Actually the Eaton -roots type supercharger is volumetric meaning that it will only alow a given amount of air through its screws at a time- anyone noticed that the lightning revs are limited far lower than those on a standard f-150? tis because above the redline on the lightning the blower actually makes it difficult for the engine to breath and can cause dead cylinders. For this reason I fail to see the why of the twin blower setup- why a centerfugal supercharger running though a roots- when at a given rpm the roots wont supply more and the air supply curve levels off- so you cant get more "top end" with a volumetric supercharger in your system.
ALthough this picture doesn't show it, the roots is bypassed at higher RPM to allow the vortech to work its wonders. This setup has been used for years in rallying, although they perfered to use a turbo in place of a supercharger for better efficiency. I believe it was Lancia who first used it in their old Delta rally car program. The idea being that the roots gives the instant throttle response and boost in the low end, preventing any power loss due to turbo lag and boost threshold. In this example, it is merely substituted for a centrifugal blower.
Maybe Rara can shed some more light on the topic, as he knows more about this particular truck I beleive.
