2 pc manifolds

[QSHIPQ at aol.com]

Doug writes:
>Flow through a ducted system (the exhaust) is related to exactly two 
parameters: >1.) The pressure available to move the fluid (exhaust gas) 
through the pipe, and 2.) >The sum of all of the local losses along the 
pathway From the exhaust valve to the >tailpipe).

Unhunh.  And the losses would include things like throat to nozzle area 
ratio, restrictions in the nozzles, the reflection of the pulses from a turbo 
blade back to the valve (reversion).  You have made a great simple summary 
Doug, it's missing a lot of the knowns as far as *what* those restrictions 
are and what effect they have.  In any turbo 10v audi, "dinging" the downpipe 
I doubt would result in ANY measureable loss of pressure or flow.  Put 
another way, the gains of the 2pc manifold outweigh this loss.  Put another 
way, if you address the downpipe restriction (the first 4in of it), you can 
do a LOT of dinging.
 
>Note: This _assumes_ that the pressure available at the exhaust valve id not 
varied >by other changes between the two systems being considered.

less reversion is a good thing, before the turbo.  Less reversion after the 
turbo in terms of "ding" theory, might be a good thing, I doubt even 
measurable.  What you are missing in your "theory" Doug, is that you are 
speaking of exhaust theory in relation to a N/A car, not a turbo car.  Just 
the pitch of the turbo blades themselves can yield gains and losses between 
valve and turbo, not accounted for in your theory.
 
>You don't get to look at just one little ding and suggest that it negates 
the >improvements that might be offered by reddened loss through a different 
manifold.  >Nor, vice versa, does the improved flow through the 2-piece 
manifold negate the >constraints imposed by its installation.  It's a 
"system," gentlemen, not parts and >pieces.

After having done 3in turbo back systems on my 10vt cars (with and without 
2pc manifolds), I suggest that ding theory is BS, and that the "system" 
benefits are pretty noticeable addressing the EM and downpipe, less 
noticeable addressing the "rest" of the system.  
 
>The only proper way to analyze any proposal is to look at the entire system 
from >the exhaust valve to the tailpipe....have some fun!

Too little information.  For more, you may want to read up on Pulse converter 
theory, turbocharger turbine theory, and Birmann PCT, and the work of Boveri 
and Sulzer wrt Birmann PCT.

Not to disagree with your proposal here Doug, just incomplete.  And in the 
application of the 10vt, ding vs 2pc manifold, just not applicable.

My .02

Scott Justusson

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