Turbo vs. Supercharger.

[nealtovsen at yahoo.com (Neal Tovsen)]

> but I've never heard of a
> "non-internal-compression" air compressor
> (supercharger) and I am very familiar with
> Roots-type blowers.

You need to read your Corky Bell book (or get one)! 

:)

Traditional roots-style blowers do not compress air
within the housing of the supercharger or between the
rotors. They compress air in the intake tubes by
"blowing" it faster than the engine can consume it.

Lysholm twin-screw SC's are internal-compression
chargers. They compress the air between the blades of
the supercharger, releasing it into the intake
pre-compressed.

Roots-style blowers aren't as efficient, but they also
have very little parasitic drag at lower RPMs because
they aren't moving enough air to create resistance, so
they mostly freewheel and only cost the power needed
to spin the rotors freely on the bearings. Lysholms
are much more efficient at compressing air, but since
they're always compressing air at a constant ratio per
revolution, they always present a fairly significant
power consumption for the engine at any load/speed.

Neal

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