[s-cars] Bypass valves - Which one?

[Joseph Pizzimenti]

Another note:

Are you CO boys using catchcans or are you getting all
that blowby into the intake/pressurizing the
crankcase?

Pizzo

--- QSHIPQ at aol.com wrote:
> My .02?  Big compressors can make huge flows with
> big HP at WOT.  Big 
> compressors can make huge flows and surging with
> less than WOT.  As I shared with 
> Mike and Scott D at Steamboat last year, you can do
> one or both of two things.  
> First, you can bypass that air out a valve on the
> intake side (pre tbody).  The 
> problem with this is it doesn't really address the
> problem, which is ON 
> boost, albeit moderate, or attempts thereof.  And,
> really big turbos don't loose 
> efficiency with "leaks" on small motors, so this
> could be an option, especially 
> on a 128ci motor.
> 
> The related second problem, more likely the cause,
> is the lack of enough 
> valve area on the exhaust relief side (read
> wastegate) to properly regulate a 
> large turbo ramping up with relatively low exhaust
> energy input (read less than 
> WOT) for the size of the turbo.  This isn't a new
> phenomenon, audisport was 
> dealing with it back in the 80's.  The real problem
> becomes the ability of 
> software/hardware combinations that will allow part
> throttle on boost situations from 
> manifesting themselves similar to being "on and off
> turbo" like being "on and 
> off cam".
> 
> Personally, I doubt a good solution will be found in
> the software hardware 
> control, short of putting more displacement into the
> motor itself.  
> 
> My baseline argument is that you want the smallest
> turbo to do the job for a 
> given motor.  Big turbos make massive HP at WOT and
> RPM, it's a volumetric 
> efficiency thing.  When you try to tackle less than
> massive HP at less than WOT 
> and less VE at a lower RPM, you may find that the
> turbo that was good for the 
> ulitmate number, may fall flat on it's face in less
> than full battle loading.
> 
> I would also venture that whatever the "best"
> solution is, will be confirmed 
> on the dyno in terms of the curve.  Instead of using
> the dyno to whack the top 
> end, why not use it to figure out what's happening
> under that?  My suspicion 
> is that you might find the problem at part throttle
> by looking at the 
> torque/HP comparos vs WFO.  
> 
> It might also be time to get these Hapersized
> magical mongo turbos put on a 
> turbo dyno.  It's not cheap, but I think the
> conclusion might become more 
> obvious wrt the problem.
> 
> HTH
> 
> Scott Justusson
> QSHIPQ Performance Tuning
> 
> 
> In a message dated 12/4/2003 9:51:58 AM Central
> Standard Time, 
> mlped at qwest.net writes:
> Hap remains in the hunt for a solution.  With out a
> running car capable of
> pushing the kind of boost that seems to generate the
> surge, I have some
> modified parts to play with, but nothing to check
> the results on.  So, in
> the interim I'm stuck with bad pilot jokes:


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