Turbo header design

[EFISYSTEMS at aol.com]

I am interested in this thread as I would like to understand better the
dynamics of a turbocharged engine.  It was always my understanding that the
reason for a header over a manifold (in a turbo application)was to equalize
the pressures at the ports,,,not for any kind of scavenging effect because
there is pressure in the exhaust before the turbo usually equalling the intake
pressure(I'm not concerned with how fast the turbo spools up at this point of
the thread,,,, only with what is happening at full boost)  I guess my question
is how could there possibly be scavenging if the exhaust has 15lbs of
backpressure(for a number)???????Greg???Anyone???
-Carl Summers

In a message dated 1/6/99 12:14:51 PM Pacific Standard Time,
clarencewood at centuryinter.net writes:

<< Subj:	 Turbo header design
 Date:	1/6/99 12:14:51 PM Pacific Standard Time
 From:	clarencewood at centuryinter.net (Clarence Wood)
 Sender:	owner-diy_efi at efi332.eng.ohio-state.edu
 Reply-to:	diy_efi at efi332.eng.ohio-state.edu
 To:	diy_efi at efi332.eng.ohio-state.edu
 CC:	bearbvd at sni.net (Greg Hermann), darkmonahue at awwwsome.com (Aaron Willis)
 
   Several years ago I read an article on the design of a collector for V8's
that produced a bolt-on 20 hp increase.  I thought the idea was very slick:
pair the tubes to their 180 out partner, baffle their exit into the collector.
In other words:  as tube #1 was pushing out exhaust the cylinder that tube #2
was servicing was on the power stroke;  as tube #2 started to extract it was
helped by the vacuum created by the extraction of tube #1 which had just
finished.
   My question is: why can't this be applied to the header of a turbo'd
engine: pre-turbo.  I know that the turbine is already turning and therefor
creating a vacuum; but, at velocities reaching .75 mach, wouldn't any tuning,
like using the 180 out exhaust arrangement help??  I don't think the header
tubes would have to be lengthened to any great extent but, the baffling would
have to be in place.  Also, wouldn't the pairing of 180 out tubes help to more
efficiently direct the vacuum created by the turbine?
 
 Just a thought....
 
 
 IZCC #3426
  1982 280ZX Turbo GL
  1966 El Camino
  1982 Yamaha Maxim XJ-1101J Motorcycle
  1975 Honda CB750 SS (black engine)
  1986 Snapper Comet lawn mower
 Clarence Wood
 Software&Such...
 clarencewood at centuryinter.net
 Savannah, TN.
 
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