[s-cars] Bypass valve thoughts. . .?

[QSHIPQ at aol.com]

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Kirby:
Comments inserted, I saw all of Beddors SQ, including the white race monster
Ned references.....

In a message dated 9/26/2003 6:03:23 PM Central Daylight Time,
kirby.a.smith at verizon.net writes:

o The throttle was upstream of the turbo
SJ  - Not on that car.  Throttle was after turbo, attached to manifold.  I
haven't seen and audi I5 any other way....  Yet.

o The auxilliary exhaust fuel injector was suffient to spin up the turbo
after compressor stalling

SJ - This car doesn't sport the aux fuel injector in the exhaust - just the
standard audi sport manifold I&E.  No one in their right mind would run one of
these unless they had a spare motor for every race.  I believe the average
life span of this setup was around 1 hour.

o The intake tract was so well tuned that the reflection of the throttle
closing pulse made it back to the intake valves at the optimal moment
after shifting

SJ - For that to happen it would have to bounce off the turbo compressor
blades first.  At which point the turbo has stalled already by definition.

o The compressor was designed not to stall at the speed it got down to
during shifting

SJ - Turbo stall is the effect of the closed throttle pressure wave causing
the turbo compressor blades to stall.  All compressors with a pressure wave on
the blades will move slower than a compressor that is freewheeling (i.e.
bypass valve or cracked throttle)

I'm pretty convinced that Lehmann just figures you keep the throttle cracked
during shifts.  Especially, if one has any experience with big turbos and that
crappy SQ bypass valve.  It rips, has bad closing properties (gets misaligned
and leaks) and really doesn't help much in race cars.  I'm imagining a Heinz
quote something along the lines of "learn to drive"....

Scott Justusson