[s-cars] Overboosting.

[Tom Mullane]

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
>