terminology and turbo questions

[james accordino]

So I'll assume by your response that they used the
full WP vanes as produced.  Usually racers cut them so
as to reduce the HP drag of the pump when not needed
to add extra cooling for ancillaries.

Jim Accordino

--- JShadzi at aol.com wrote:
> The TransAm cars used a stock pulley with the cog
> all drilled up to reduce weight.
>
> Javad
>
> > I'm interested in hearing responses to this thread
> as
> > well.  I wanted to post something about this when
> > someone wrote about underdriven pulleys to reduce
> > parasitic power losses.  We used to clip the vanes
> on
> > the water pump for the same reason.  It actually
> takes
> > quite a bit of power to drive the WP.  I don't
> know
> > that I'd try this on an Audi though.  I wonder
> what
> > the race teams did?  Clip the vanes or run an
> electic
> > drive to the WP?  Anyone know what they did,
> although
> > I don't know if it has any relevance to street
> driven
> > Audis.
> >
> > Jim Accordino
> >
> > --- auditude at neta.com wrote:
> > > JShadzi at aol.com wrote:
> > > >
> > > > << Also,  the psi rating of a turbo....
> > > >  Is this the pressure on the turbo outlet,
> pushing
> > > into
> > > >  the intake?>>
> > > >
> > > > Well, turbos are not rated for psi per se, but
> > > typically the actual
> > > > psi output is measured in the intake manifold
> > > where it counts.
> > > >
> > > > << Or, is this the pressure of exhaust acting
> on
> > > the
> > > >  turbo spooling fins?  >>
> > > >
> > > > No, that pressure is typically not measured,
> as
> > > what is really
> > > > important is in the intake manifold.
> > >
> > > Would it be a correct statement to say that
> > > "clipping" mods done
> > > to the exhaust turbine fins results in better
> > > performance, due to
> > > less backpressure of the exhaust getting out of
> the
> > > motor?  At the
> > > expensive of boost onset rpm (is that different
> from
> > > "boost lag",
> > > which is said to be different in Max Boost)?
> > >
> > > At some point, the turbo can be too small, and
> be a
> > > restriction to
> > > the output of the exhaust, right?
> > >
> > > I realize this is a different topic than where
> the
> > > thread was, but it's
> > > a factor too, isn't it?
> > >
> > > Is the backpressure created by the turbo a
> factor in
> > > its efficiency
> > > for a certain pressure?  I know that clipping
> > > changes the a/r, and
> > > that it makes it "act" like a larger turbo, but
> is
> > > this simply due to
> > > the decreased backpressure?  Or, does it have
> more
> > > to do with the
> > > new shape of the fins and the new angle at which
> the
> > > exhaust
> > > gases hit them?
> > >
> > > Thanks,
> > >
> > > Ken
> >
> >
> > __________________________________________________
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>
>


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