[s-cars] Overboosting.

Sun Sep 11 19:28:10 EDT 2005

Wow....that is puzzling if you have swapped ECUs.  Have you checked the
grounding to the ECU...real longshot here but you are right this one is
tough.
--Calvin

  -----Original Message-----
  From: Tom Mullane [mailto:tmullane at gmail.com]
  Sent: Sunday, September 11, 2005 4:49 PM
  To: calvinlc at earthlink.net
  Cc: S-CAR-List at audifans.com
  Subject: Re: [s-cars] Overboosting.

  Right now the boost gauge is T'ed into the line from the WGFV to the WG so
I can see when the valve sends pressure to the WG to open it.  TheTDS-1
interfaces with the ECU and displays the boost that is reported to it by the
transducer, which is a VMAP.  When I had the analog gauge set up to read
boost (prior to TDS-1 installation) it was T'ed into the line that feeds the
ECU about 6 inches before the ECU.  I'm pretty sure the this vacuum line is
OK, but I am willing to try anything at this point.  I will run a new line
directly from the engine to the ECU for testing.

  As far as an internal fault in the ECU, that has been eliminated as a
possibility.  Marc S and I have been swapping ECU's back and forth and the
problem always stays with my car.

  This is a puzzler.

  Tom

  On 9/11/05, calvinlc at earthlink.net <calvinlc at earthlink.net> wrote:
    Tom,

    Take the same boost gauge T you made and remove it from where you had
it.
    Now make the hoses the proper size to put the T directly at the input to
the
    ECU.  This will verify that the boost pressure going to the ECU is the
same
    as that seen elsewhere in the system.  If it's not the same then
obviously
    the most likely culprit is the hose routing from the engine compartment
to
    the ECU or a boost leak internal to the ECU.  If the signal is the same
then
    it has to be inside the ECU and you most likely have a bad pressure
sensor
    or bad solder connection inside the ECU.  If you had your pressure
sensor
    replaced, which I am sure you did when you went to an RS2 type setup,
then
    it may very well be a bad solder joint.  If it's either of these I would
    think that a swap to a V-MAP boost sensor might be a good next step.

    --Calvin

    -----Original Message-----
    From: s-car-list-bounces at audifans.com
    [mailto:s-car-list-bounces at audifans.com ]On Behalf Of Tom Mullane
    Sent: Saturday, September 10, 2005 10:29 AM
    To: S-CAR-List at audifans.com
    Subject: Re: [s-cars] Overboosting.

    Update:
    First off, thanks for all the ideas, and thanks to an unnamed lister for
    the unsolicited loan of a known good MAF and another lister for a WG
loan.
    At this point, in addition to the things I tried in the original email,
    I've also changed the MAF and WG with no improvement, and I've done some
    monitoring of the WGFV activity. Currently I have T'ed a boost gauge
into
    the line running from the WGFV to the WG so I can see when boost is
being
    routed to the chamber to open the WG. I've also tapped a dwell meter
into
    the wires feeding the WGFV so I can see when it is receiving a signal.
I've
    installed a normally closed pushbutton switch in series with the WGFV,
    allowing me to cut power the switch, route boost to the WG and thus
knock
    boost back to 7 psi at the push of a button. Both the meter and gauge
are
    taped to the outside of the windshield, giving the green monster a very
    slick ricer look. Cops dig it.
    Everything seems to point to the ECU calling for this high boost. The
WGFV
    receives a signal (causing boost to rise) even when boost is at 31.5
psi.
    Depress the pushbutton and dwell falls to zero (duh - no power) and the
    boost gauge shows pressure immediately routed to the WG , causing the WG
to
    open and boost to fall. On the highway in higher gears under load, boost
is
    at 31+, and the WGFV is still receiving a signal from the ECU causing it
to
    stay open and allow overall boost to build.
    In summary, my testing show that the WGFV, assorted plumbing, and the WG
    are all working as designed, but the ECU demands more boost.
    Help.
    Tom

    On 9/2/05, Tom Mullane <tmullane at gmail.com> wrote:
    >
    > Folks,
    >  I have a strange problem with my 95.5, and I can't seem to get to the
    > bottom of it. The car will overboost to 30+ psi in fourth and fifth
gears.
    I
    > assume it would do the same in the lower gears, but it accelerates
fast
    > enough so that pressure is unable to build to these levels.
    >  Some background: The car has 82k on the clock, RS2 EM and turbo,
    > Stromung, 34 lb/hr racetronics injectors, stock MAF, Hyperboost BPV,
and
    > Mihnea's custom tuning. Wastegate spring is at the factory setting.
There
    > are no boost leaks or ingition problems. Since Marc S is running a
nearly
    > identical set-up (034efi turbo and stock exhaust are the only
    differences),
    > I have been swapping parts back and forth between our two cars,
attempting
    > to isolate the issue. Marc's car runs about 26 psi.
    >  So far I have:
    > Reverted back to Minhea's "off the shelf" standard chipset for the
RS2/34#
    > combination
    > Swapped ECU's
    > Swapped the altitude sensor
    > Installed a new WGFV
    > Unplugged the electrical portion of the WGFV and observed 7 psi max
boost
    > Swapped the wastegate
    >  Since I just recently started running an installed boost gauge, I
have no
    > idea how long this problem has existed. I suspect it was there even
last
    > year when Mihnea tuned the car. Before we went out, he had he uncap
and
    > crank the WG down 3 turns, but after the tuning he told he to crank it
    back
    > out 2 turns.
    >  I'm running out of ideas. Anyone?
    >  TIA
    >  Tom
    >
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