[TR] Superchargers

[Randall]

> Does anybody have recommendations and/or experiences with Judson
> superchargers? I am actually thinking of picking up a rebuilt one for
> my 190SL.

Unless being period correct is important to you, I would highly recommend
using a Roots-type blower instead, preferably with a "priority valve".  The
Judson blower design is considerably less efficient, which means it both
sucks more power and heats the intake air more, which in turn makes
detonation much more likely.  And detonation can literally destroy the motor
in a matter of seconds!

The Judson uses phenolic vanes (although perhaps yours will be rebuilt with
a more modern plastic) that wear and shed particles directly into the engine
intake.  The original TR and MG setup (likely your MB will be similar) is
also a "full time" blower, meaning it is always compressing the intake air
(and drawing significant power) even when it is not needed (throttle plates
are closed).  The modern designs use a "priority valve" to bypass the blower
when it is not needed (and some even have a clutch to let the blower stop
turning altogether).

Because of the rubbing contact surfaces inside the Judson, it also requires
a steady supply of oil through the intake.  Although the original oilers
were made by Marvel, the oil should be motor oil, not Marvel Mystery Oil.
The oil also tends to promote detonation.

All that said, I do have a TR3 Judson stashed away, that I hope to be able
to try out some day.  Most likely I'll also install water injection and
boost retard, to control detonation.

PS, the factory MB superchargers are Roots-type, made by Eaton I believe.
Some of them include the priority valve right in the blower housing.

-- Randall