RE: CC "Up to" - may just include Newtons (/Murphy's) Law

[QSHIPQ@aol.com]

I'm thoroughly enjoying the chemistry and physics lessons on turbos, CC, and 
basic exhaust theory.  Obviously, many have great ideas, regardless of the 
plethora of text written.  To interrupt just a second, let's throw some real 
data into the mix.

Exhaust gasses into the turbo.
The boys at audi spent some time on this, they measure EGT *right before it 
enters the turbo* (2pc EM's have a port for EGT measure already in this 
location.  The thinking is that since the turbo scroll itself is hottest, the 
easiest measure of hot side temps is less than 1 inch from the peak), here's 
some real data for you guys to compare "theory" to:

btdc          Mix strength         EGT (degrees C)  EGT tempF (converted)
20              weak                   860                     1580
20              rich                     815                     1499
30              weak                   786                     1447
30              rich                     715                     1319

The concern of this paper (SAE 880258) is the heat soaking of the center 
bearing in running and stationary tests.   Those with CC in mind may want to 
gander at this paper first.  Here's an interesting summary for the CC'ers 
(the wording of this text is for reproducing a bench test for turbocharger 
testing):

"Turbocharger centre Housing Casing Temperature:  This has to be high both 
during the conditioning part of the test (in excess of 180c > 356F) and 
during the run part of the cycling test (in excess of 220c > 428F).  The peak 
heat soak back temperature during the cycle must be in excess of 300c > 572F. 
 Going to excessively high soak back temperatures leads to cracking and 
distortion of the turbocharger  turbine housing and exhaust manifold and 
distrotion of the turbocharger centre housing without necessarily reproductin 
field failure (carbon buildup) type deposits."

I encourage anyone looking at CC to read the above a couple times.  CC the 
manifold concentrates *more* heat in the center bearing.  Again, all physics 
nerding aside, this information shows that theoretical idealism of CC may 
have the exact opposite outcome.

Nerd away boys.  For more reading try: Pulse converter theory, Birmann Pulse 
converter, de Laval convergent-divergent nozzle.

HTH

Scott Justusson
QSHIPQ Performance Tuning
'87 5ktqwRS2 -10vt
'84 RS2URQ -20vt
'87 4Runner turbo - RESQ