[s-cars] safe boost limits

[QSHIPQ at aol.com]

Reading these two posts, my advice:  IF you don't know exactly how the S car
boost system works, don't play.  Wastegate creep is a function of a boost
controller hooked to the top of the wastegate, NOT the bottom of the
wastegate (ala S car).  Eliminating the WGFV will give you baseline spring
pressure, in stock trim that's 1.3bar (.3bar boost).

Adjusting the WG preload on an S car really shouldn't be necessary IF the
WGFV is operating correctly.  You *can* do it, but you are compromising the
safety shutdown feature of the WGFV circuit.  If a problem is sensed in the
boost circuit, or 3000ft is sensed by the altitude sensor, the WGFV will shut
down (remain open all the time) or is open more (alt compensation)
respectively.  When you increase the preload, or run a stiffer spring, you
are telling the computer that there is nothing wrong.  Er, "begging to
differ" could cost you a motor.

WRT Boost controllers, you guys should reread Rob P's post on the subject a
few months ago.  He confirms what I've been chirping for years, the BEST
boost controller is already on your car.  A move to an aftermarket boost
controller decreases your available boost tables ten fold.

I've seen a lot of messed up tweeked S cars come thru my shop.  Most of them
are the result of someone not knowing how the system works, including all
it's *advantages* in proper function.  Most bring me the disadvantages of
improper function.

My .02

Scott Justusson
QSHIPQ Performance Tuning
RS2URQ Project


In a message dated 9/18/02 4:12:51 PM Central Daylight Time,
James.Murray at ericsson.ca writes:


If you take out the WGFV won't you need to replace it with something?
Otherwise you won't get any boost at all. I assume your considering a manual
boost controller, this would effectively also stop wastegate creep if setup
correctly according to the AutoSpeed article.

For the limp mode condition, you could put a bleeding device that keeps the
sensor from seeing more than 2.5 bar.

Rod is much more of a real life expert, he might have more insight, since
I'm just doing bench mechanics at the moment... no real BTDT...

/J.

 -----Original Message-----
    From:    Mark Strangways [SMTP:strangconst at rogers.com]
    Sent:    September 18, 2002 4:22 PM
    To:    S4audinut at aol.com; KrasuskyP at FirstInterBank.com;
s-car-list at audifans.com
    Subject:    Re: [s-cars] safe boost limits

    So, with that in mind, if I take out the WGFV and just splice it
straight
    into the wastegate thereby allowing boost directly to the turbo all
the time
    what boosts would I get ?

    Assuming that I need to "wind" the spring down, is that meant to say
that I
    have an adjustable wastegate ? Or simply , just put the stock one
back in.
    Secondly, is it the overboost that is causing the limp mode to be
activated
    ? Basically, what happens is the car will drop boost down to 1.1,
1.2 Bar
    abs. until a restart. And that is all that is available in any gear
during
    this mode. Any attempt to go above this boost results in a most
dramatic
    loss of power.

    I have thought of getting a spare WG lid and making an adjustable
spring
  saddle. Anyone ever use one ? Are they worth while ?