View Single Post       04-11-2010, 03:39 PM   #5 M&M's Avatar
Drives: E92 M3 Competition Pack Join Date: Mar 2007 Location:
Johannesburg, South Africa  Posts: 659 iTrader: (0)  Originally
Posted by e.n335 View Post A centrifugal type supercharger does
not provide absolute boost like a turbocharger, it provides
relative boost due to the fact that the speed of the compressor
is directly related to the engines rpm. A super provides
"absolute boost" just the same as a turbo does. A CF blower and
turbo are essentially the same except one runs off exhaust
gasses and has a wastegate and the other runs off the crank. I
don't follow the second part of the sentence. Due to speed of
the compressor being related to the rpm? The rpm range is the
same at sea-level or at 5000ft. The car will rev from idle to
8500rpm at both elevations. So every revolution of the crank
will produce the same amount of boost and spin the same amount
of air into the engine at sea-level and at altitude.  The
difference being that the air is less