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Re: Turbo and motor photos

To: grbyrns@ucdavis.edu, wmgilroy@avaya.com
Subject: Re: Turbo and motor photos
Date: Thu, 1 Feb 2001 15:18:31 EST
Cc: spridgets@autox.team.net
If I understand this correct you are wondering why the inlet gases don't back 
flow on a turbo inlet at half throttle?

The engine is sucking on the carb at half throttle, the turbo compressor 
(driven by the turbine) is pushing air in the same direction.  Why would the 
gas backflow?

What can happen is that you shut the throttle plate and the turbo compressor 
(still being driven by the turbine which has not yet wound down) is pumping 
air against a closed throttle plate which can lead to compressor stall.  The 
solution is to fit a dump valve (not to be confused with a waste gate - which 
bypasses exhaust gas).

Daniel1312 

In a message dated 01/02/01 09:42:45 Pacific Standard Time, 
grbyrns@ucdavis.edu writes:

<< Bill,
 
 While I'm no expert on the subject either, I think the answer is in the vane
 design.  There is only pressure on one side of the 'pump'.  The induction
 vanes are shaped somewhat like the agitator in a washing machine.  The
 incoming gas stream comes in down the middle and is thrown to the outside
 where the port to the intake manifold is.  For gasses to go back out the
 carburettor would be like something trying to go down in a hurricane vortex.
 If you remember the old "tilt-a-whirl' amusement park rides where you are
 pressed to the walls of a rotating cylinder and then the floor drops away,
 could you imagine trying to pry yourself off the wall and moving toward the
 center of the cylinder?  Just in case my explanation is off base,  I'm
 cc'ing this to the list where more turbo-knowledgeable minds will set us
 both straight if needed.  And of course, the knowledge-less will post about
 how much noise a cat makes when its tail gets caught in a turbo.  Gee, I
 sort of wonder about the answer to that one myself.
 
 Regards,
 Glen Byrns
 '59 bugeye
 '59 Morris Traveller (Winifred)
 
 >
 > What I still don't understand (bear with me) is the case where the car
 > is running at say 3K RPM, and the throttle is 1/2 open.  I would think
 > that the pressure in the manifold from the turbo would go into the
 > cylinders when the intake valves opened.  I would also think that it
 > would go out the carb throat since the throttle is 1/2 provide a path
 > for the compressed air travel.  I believe that that is not the case but
 > I don't understand why.
 >
 > Bill Gilroy
 >
 > PS.  I didn't ride the short bus to school :-)

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