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Re: Intermittent Boost
In a message dated 96-08-25 05:54:47 EDT, you write:
<< Eventually, of course, boost level will fall to the point at which the
computer no longer has to intervene to open the wastegate.
I'm beginning to believe that the length of the overboost control cycle
(the duty cycle of the overboost control valve, if you like) is a more
important indicator of health in a servo-controlled turbo engine than
the boost level, because the system can control the latter to cover an
increasing level of sickness. Just like doctors take pulses as well as
It would be fairly easy to design a circuit to monitor the duty cycle,
and even easier to devise an alarm that would be triggered by
non-operation of the valve after n seconds of the "full load" switch
being on. The cycle changes with air temperature and pressure, of
My 1988 ur-quattro has a cycle length (guessed) of just over a second
uphill in third gear at sea level. I would have expected yours to be
shorter, but it's a hard call. Perhaps other owners of the same vehicle
could comment. >>
A good and cheap indicator would be to install an LED for the WG solenoid...
After a couple weeks of watching when it kicks in, one can easily detect
when it is not operating correctly... If you ripped the IC to t-body hose
one would notice that the LED will become more intermittent in it's
behavior.... It's an easy two wire hook up, and the T1 LED can be put
wherever you can drill a 1/8" hole...