[s-cars] Re: Living at altitude - Apexi and turbos

[Kirby Smith]

I use the A'pexi mainly to keep first gear boost down to save my tranny.

Its not obvious that snappiness implies that I am operating to the left
of the surge line. If I were, the overall response should be worse.  In
any case, vehicle acceleration loci on compressor maps tend to start by
moving to the right.  Normally they bend and end up roughly parallel to
the surge line; crossing over the line occurs late in the gear, not
early where the concept of snappiness applies.   Just think of the
A'pexi as a lower-creep top-control waste-gate controller design.  Isn't
that what was used on the 5000?

I see no fundimental functional difference between a frequency valve and
a stepper motor.  Either can regulate the flow of control air, and I
estimate that a frequency valve can do so with better bandwidth.  I
doubt that there is anything that can happen to the turbo state in less
time than the A'pexi can react, although something might occur faster
than the WG can react, but in that case even the OEM design cannot do
any better.  You may argue that neither the A'pexi valve or the OEM
valve are large enough for some applications, but that is a different
issue.

kirby