Subject: Re: [TR] Got Judson

From: Randall <[email-masked]>
Date: Fri, 23 Aug 2013 16:04:25 -0700

---- Jeffrey Gayton <[email-masked]> wrote: 
> Though very VW oriented, there's a lot of good Judson info. They seem to have
> a more positive view of it's reliability (both the supercharger and the car).

Possibly it does work out better on a Bug motor.  One of the problems is that the Judson design is relatively inefficient, meaning it generates a lot of heat and consumes a lot of power for the amount of boost that it produces.  And at least some of the heat is generated all the time, even when not using the boost.  The blower is always compressing the inlet air, even when the throttle plate in the itty bitty 1BBL Holley carb is throttling down the engine for cruising.  Hot fuel/air mixture makes the engine more apt to detonate (knock), as of course does running boost in the first place; and the stock TR motor doesn't have a lot of margin to begin with.  There is a reason that the factory recommended 95 octane fuel.  The oil being mixed with the fuel/air doesn't help either (oil has a horribly low anti-knock index).

Modern blowers (like the kit Moss sells) use a more efficient compressor design (so generate less heat for a given boost & flow) and a bypass valve so it doesn't generate heat (and waste power/fuel) all the time.  I believe (not certain) the Moss kit also includes provisions to retard the spark while running under boost, to keep the timing optimum and further reduce the chances of engine-destroying knock.

Randall

** [email-masked] **

Archive: http://www.team.net/archive