Re: twin turbos?

[Jeremy R King <kingjer@eng.auburn.edu>]

On Wed, 5 Jun 1996, Graydon D. Stuckey wrote:

> On Wed, 5 Jun 1996 ptimmerm@mashtun.JPL.NASA.GOV wrote:
> 
> > Turbo Scott said wrt twn turbos....
> > 
> > ...  Might want to look at the Lancia Rally car concept, it has 
> > more validity to the audi than a twin turbo would.....
> > 
> > If I read him right, he is implying that the addition of a
> > supercharger to the existing turbo system would be a better
> > idea.  With other massive turbo apps like tractor pull rigs
> > or hydroplanes, they run sequential with cooling at each
> > stage.  So you compress, cool, compress again, cool again,
> > then run it into the motor.  How about a g60 front ending
> > a k26 derivative with stock intercooler plus another small
> > one after the g60?  As scott is fond of saying its FLOW no
> > pressure you want.  Who will be the first?
> 
> The trouble with a sequential setup like that is that you will always be 
> limited to the maximum flow capacity of the smallest Xcharger.  What we 
> want is a parallel system, in which the ECU can choose between a 
> supercharger (fro low RPM throttle response) OR a turbo charger (for high 
> rpm power)  The trick is being able to transition between the two systems 
> smoothly.  Not rocket science, but difficult nonetheless.
> 
> Later,								
> Graydon D. Stuckey								
> graydon@apollo.gmi.edu								
> Flint, Michigan   USA
> '86 Audi 5000 CS Turbo Quattro, GDS Racing Stage II				

I agree with your statements about the sequential setup.  I'm curious
about how you would run a parallel system.  Would you have the
supercharger feed the motor and all the exhaust go to the turbine to spool
it up with the compressor dumping to the atmosphere.  Then switch to the
compressor feeding the motor with the same exhaust setup (except that the
compressor now feeds to the motor)?  I say "motor" in the southern sense
that it actually means "engine".  It wouldn't make sense to run the super
and dump the exhaust to the atmosphere (via muffler) and then switch over
to a turbo system.  Then there would still be spool-up time.  Seems to me
all the control would be in the intake manifold.  Maybe a plenum with two
inlets (one from supercharger, other from turbo compressor) that were each
valved.  And maybe a clutch system on the supercharger to limit drag at
high rpms.

Jeremy R. King
'86 VW Quantum GL5
Drilled air box, Hollow cat (sshhh!), Dynomax Glasspak, Slow as Christmas
Sure sounds good, though!
Auburn University, Alabama, USA