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RE: superchargers

To: Neil Sherry <>
Subject: RE: superchargers
From: "Dodd, Kelvin" <>
Date: Tue, 21 Dec 1999 12:11:24 -0800

        Current supercharger technology uses a recirculating system for off
boost conditions on many units.  The vanes spin merrily without pressurising
anything.  No pressure, little drag.  There are slight mechanical losses due
to bearings, belt and tensioner.  When vacuum drops due to the throttle
opening, a vacuum operated valve recirculation valve closes allowing the
boost to build.  Since the vanes are already spinning, boost build up is
related to how fast the valve closes.  Valve closure is related directly to
engine vacuum drop.

        This system gives a smooth boost which comes on under demand.


> -----Original Message-----
> From: Neil Sherry []
> Sent: Monday, December 20, 1999 2:55 PM
> To:;
> Subject: Re: superchargers
> The car you refer to would be a Z-type. The Y-Type was also a 
> saloon but was
> powered by the XPAG engine (same as MG TB etc). There is a 
> Y-Type in the UK
> which benefits from a Shorrock blower (owned by Frank 
> Vaultier - not sure if
> my spelling is right). Makes a 'distinctive' noise and moves 
> quite well.
> As to the strain on the bearings, don't forget that with a 
> supercharger the
> crank etc have to develop the power to drive the blower. For 
> similar power
> outputs turbos are generally kinder to engines.
> Neil
> -----Original Message-----
> From: <>
> To: <>
> Date: Monday, December 20, 1999 9:01 PM
> Subject: re: superchargers
> > The 50's "baby Jag"  MG sedan, I believe it's the  MG YB, 
> had a Shorrock
> >available, It runs on the MGA based "B" series motor. 
> There's one running
> >around the SF Bay area that belongs to Skip Kelsey, who owns 
> "Shadetree
> >Motors" (garage-front moss distributer) I don't have his 
> email address handy,
> >but last I checked, he has an ad running in MG Driver 
> (NAMGBR)  Perhaps he
> >can give more details. It is certainly preferable to a 
> turbo, apparently much
> >less strain on the bearings due to the more gradual build-up 
> of power.

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