Turbo header design

[Gary Derian]

A turbo raises both the intake and exhaust pressure.  Scavenging works when
the local pressure is reduced during the exhaust stroke or a pressure drop
is created across the combustion chamber during overlap.  Relative low
pressure can be achieved even though the general pressures are above
atmospheric.  Its like running the engine on Jupiter.  A really efficient
turbo setup can have a higher intake pressure than exhaust but most street
installations have higher exhaust than intake.  Even an atmospheric engine
has higher exhaust pressure than intake at WOT.

Gary Derian <gderian at cybergate.net>


>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