Date:         Fri, 30 Sep 2005 20:24:44 +1200
Reply-To:     Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Subject:      Re: yet another engine choice - VW "twincharger"
In-Reply-To:  <5672-433BE49A-1944@storefull-3171.bay.webtv.net>
Content-type: text/plain; format=flowed; charset=us-ascii

>Wrong on all counts Andrew.

not at all.

>That is unless your running a P-40, P-38, P-51 A, and want to run your
>Allison V-1710 at 30,000 ft. and want to elude the Red Baron.

Nope... vewry poor performers. None of those aircraft were
competitive. Crude pushrod stuff. To Make the Mustang competitive
they had to fit an ENGLISH engine. MUCH rather have a Daimler Benz
DB605 or a late Junkers Jumo, thanks. Now, THERE was an engine. The
605  powered the one of the fastest as well as the very
fastest-climbing WWII fighter (Bf109K) and the fastest piston-engined
aircraft ever (Dornier Do335 Pfiel).

>And even with your mis match of mechanical terminology, your not even
>close.
>
>The turbosupercharger as you want to call it was engine driven.

OK, so those were solid-drive. So what? That doesn't alter the fact
that ANY meachanism which supercharges an engine is a supercharger.
That includes exhaust-driven superchargers. Simple English. WHAT do
you find so difficult to understand, Robert?

>A Blower ( supercharger ) is engine driven, any turbo is exhaust driven.

A turbo is a blower.

>Do this.
>Stop by your local clsas 8 truck dealer and ask them to sel you a turbo
>for your KT 450A Cummins.
>
>Watch what they throw on the counter in front of you.
>
>You may be amazed.
>
>You'll see in that box an exhaust driven turbine.
>You won't be seeing a gear drive GMC blower. ( supercharger )

So? What sort of supercharger they fit to GM trucks isn't relevant to
this topic.

>What your running won't handle either of these item's anyway so why
>worry about it?

How would you know?

>Bolt a Rolls-Merlin into them VW's, and then maybe you can use that
>Turbo Super Charger your talking about.

Merlins weren't supercharged.  The DB600-series was.

>It's just a play on words back from the 40's from down under,  but a
>blower will always be a belt driven, or gear driven supercharger, and a
>turbo is an exhaust boost.

It has nothing to do with Down Under.A supercharger blows air into
the engine. It's a BLOWER. Turbos, of course, do this. The type of
drive is irrelevant to the word "supercharger"

>Maybe Andrew is flying his VW's at 35,000 feet and needs some more HP in
>the thin air.

I think YOU need a little erudition... not the least in spelling and
punctuation.

>Re: yet another engine choice - VW "twincharger"Right and wrong.  A
>turbocharger is a supercharger, however, it gets it name from the fact that
>it uses a turbine to spin the compressor.  The turbine is spun via exhaust
>gases.

There you have it. I suggest that Robert learns something, instead of
remaining deliberately ignorant. Doe he call dampers "shock
absorbers"?

>Actually, A turbocharger, besides usually being exhaust driven, uses
>vaned wheels to move a large volume of air, usually working at very
>high speeds. The centrifugal action of the wheel creates the flow or
>pressure similar to the way a centrifugal pump works. Superchargers
>are usually rotary screw or lobe pumps, belt driven. The major
>significance is that they are positive displacement pumps. Even the
>VW G-Ladder is a PD pump. They need to be belt driven since as a PD
>pump, if it is not turning, air will not flow through it.

Vane (eg Roots) and I believe lobe-type pumps are not
positive-displacement. This is in part why the Roots is such a POS.
Turbos are not PD either, but then, they don't need to be to work
well, as the design makes up for any leakage by the velocity (speed
in a given direction) of the air leaving the impeller.

Basically, an engine driving a PD supercharger will strangle if the
charger stops turning for any reason (eg broken belt). A nonPD
charger will impede airflow into (and in the case of a turboo, out
of) the engine but should not stop it running.

All superchargers, including turbos, are air (or gas) pumps. The
turbo (including Paxtons) are centrifugal pumps indeed. As Jeffrey
says, turbos use a small turbine to push the air. Its impeller is
also a turbine.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<andrew.grebneff@stonebow.otago.ac.nz>
Seashell, Macintosh, VW/Toyota van nut

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