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Re: Thanks for your help, I'll have to find scope and looK! Posted by TonyJ [Email]  (#407)  [Profile/Gallery]
(more from TonyJ) on Mon, 10 Nov 2003 22:00:12
In Reply to: Thanks for your help, I'll have to find scope and looK!, Bill Homer  [Profile/Gallery]
, Fri, 7 Nov 2003 12:27:29
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Your explanation of how the BPC works is right-on. We are having a similar low boost issue (see"Brain Transplant to fix Low Boost?" thread. I didn't have a scope available, but was able to rig a two-conductor cable to the 2 coils of the BPC valve and read the "average' voltage on a Fluke DVM while the car was driven by my son. See our post for the results. The Saab shop manual shows the waveforms, which appear to have about 10% dutycycle alternating between the two coils in the example . Frequency is 70 or 90 Hz, depending on RPM. After each "on" period (voltage held near ground), there is a positive transient probably caused by inductive kick from the coil. This may have distorted my measurements, which appeared to reveal a very low duty cycle. At idle or under light load, you will only be able to see the waveform for the coil that reduces boost (the source of the buzzing). The car needs to be driven under load to excite the "increase boost" coil.
TonyJ 94 Aero, 93 CSEt, AndyJ 95 Aero (low on boost), 92 S
posted by 24.91.82...
, Thu, 6 Nov 2003 08:08:28, Thu, 6 Nov 2003 09:37:25, Thu, 6 Nov 2003 12:09:56, Fri, 7 Nov 2003 12:27:29, Mon, 10 Nov 2003 22:00:12 <-- Viewing This Message
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