[s-cars] Overboosting.

[Tom Mullane]

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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