CPU controlled boost, 5000CS TQ boost

[scott.john.mockry@bangate1.tek.com]

>glen asked:
>What are people's thoughts on totally disconnecting all the CPU crap =
>from the WG and controlling the boost the good-ol way - simple spring =
>pressure ala the ur-q?

glen,

On my 89 200TQ running "without" the CPU controlled WG solenoid  system  works ok with
 some minor  differences in the boost profile. I reviewed my previous boost data when I 
did tests in 4th gear (3000 to  5500 RPM with an outside temp around 75 degrees and at 
800ft elevation) the stock system allowed a brief period ~1 seconds of higher boost
 (~1.5bar) which shows up on the boost graph as an initial boost bump that fades back 
down to the 1.4bar level after 3-4 seconds as the RPM is increased. The stock system 
continues to reduce the boost slightly as the  RPM increases. The stock system took 
~ 1 second to go from 1.0 bar to 1.5 bar.

Using  a stiffer WG spring with the CPU solenoid connected but with the stock boost
map (overboost cutoff raised to 1.9)  the boost level rises a little quicker
(0.8 seconds to get to 1.7 bar)  to the point where the WG opens and then the boost 
output is basically flat with a slight decrease as the RPM increases. 

Using the above mentioned stiffer spring but disconnecting the WG solenoid hose
(upper waste gate chamber is left open to atmosphere) the boost rises a little 
slower (0.9 sec) to 1.7 bar but then continues to increase to 1.8 bar over the next
two seconds and then rises a little as the RPM continues to increase.

I read through the SAE article #860103 on the 86-88 1/2 5000 turbo and found the 
following:
"The dynamic pattern of boost pressure build-up can be influenced by the boost pressure
control system. For rapid acceleration, excess boost can be obtained for a limited period." 

It would appear from these tests that the CPU controlled WG solenoid can help the boost rise a
little quicker and could be setup to allow a short initial overboost condition and then
reduce boost at higher RPM to avoid destructive detonation. This overboost condition may
be what others have experienced during the  initial cold to warm running phase.

It looks like I need to get cracking on that EPROM code dis-assembler program and finish
what I started!

Scott M.