[s-cars] Re: Bypass Valves and Pressure Losses - the basics first

[QSHIPQ at aol.com]

Too much boost pressure pre tbody when the throttle is slightly cracked is 
NOT a BPV 'problem'.  By your definition, you are using a bleed type solution to 
a "on boost" problem.  I continue to argue that on a large turbo/small motor, 
this will be a tail chase that will suck cash.  By definition, "before the 
BPV opens to vent this excess pressure" means that the throttle isn't closed 
yet.  Yes?  Cuz if the throttle is closed, the BPV should be open.  Yes?

"I experimented with a too short spring that allowed the BPV to stay open a 
little and the problem disapeared totally". Well, that indicates to me this has 
EVERYTHING to do with the wastegate/turbo.  What this indicates to me is that 
the turbo is so big, at part throttle it can supply the engine needs AND the 
bypass bleed with better performance than without the bleed.  That's a 
wastegate problem by definition.  OR one could call it a turbo problem (I would).  My 
bet is that a smaller turbo will yield the best solution.  I also claim in 
doing so, performance shouldn't decrease either.

If you insist on chasing the BPV as the "solution" to a turbo problem then 
I'd suggest multiple valves with staggered openings in different locactions as a 
possibly better avenue to pursue.  For further point of reference, look at 
Ned's trivia stumper of a couple months ago.  Lehmann didn't use a BPV in the SQ 
because the Big IC (Lehmasized) became the buffer to compressor stall.  You 
already have the Big IC Hap, AND you have compressor stalling problems.  That 
just doesn't seem like a BPV solution to me.  But if you insist, then:  Dump 
more quicker.

Scott "tryin to understand Haperspeak" Justusson


In a message dated 12/18/2003 9:44:43 PM Central Standard Time, 
CaptMagu at aol.com writes:
Gee Scott

Let me see if I can explain this to you. When I say boost surge at throttle 
lift, I'm talking about too much chharge air in the plumbing before the 
throttle body. This happens before I get to vacuum on the other side of the 
throttle 
body and consequently before the BPV opens to vent this excess pressure. This 
is manifested by a surging and sort of bucking feel. The last few steps i've 
taken in shortening and softening the BPV spring have had a dramatic effect 
to 
improve but not totally solve this problem. I experimented with a too short 
spring that allowed the BPV to stay open a little and the problem disappeared 
totally. This has nothing whatsoever to do with the wastegate!!!

Hap, tryin to expain to old SJ in Everboost, Magfuire