engine/turbo theory question

[JShadzi at aol.com]

In a message dated 10/11/00 6:40:14 PM Pacific Daylight Time, 
marcswanson at mediaone.net writes:

<< i was discussing turbocharges with a friend - well,
 >  explaning them, actually.  he raised a question that
 >  i never thought of:
 >
 >  is there any overall power loss that comes from the
 >  pressure (backpressure?) required to turn the turbo?
 
 Yup.  Essentially, if you were to remove the boost effect of the turbo (say
 by leaving the wastegate always open), the NA equivalent engine will produce
 more power than the non-functioning turbo engine.  This is one of the topics
 covered in Corky Bell's book:  Maximum Boost.
  >>

    Yes, but don't forget that it is the restriciton of the turbo that builds 
pressure in the exh. manifold to spin the impeller of the turbo.  If the 
turbo did not cause any restriction, there would not be enough pressure in 
the exh. man. to spin the impeller.  All in all, it is not really an issure, 
and is calculated into the efficiency of the system.  That energy that would 
normally be wasted out the exhaust is used to pressurize the combustion 
chamber to make more power-a good thing overall  =)
Javad