Turbo header design

[Ken Kelly]

I haven't been involved in this thread, but let me point out
that scavenging is associated with the Dynamics of the
pressure, not the static average value. If you ignor the
static pressure rise do to the turbo blockage you will still
find the dynamics of the individual exhaust pulses. These
pulses can still be timed to cause scavenging. The negative
pressure that follows the pulse will be negative relative to
the pulse, but not in an absolute sense.

		Ken

EFISYSTEMS at aol.com wrote:
> 
> 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.
> 
>   >>