[s-cars] Overboosting.

[calvinlc@earthlink.net]

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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