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Yes Posted by Ari [Email] ![]() ![]() In Reply to: Is the APC solenoid supposed to click upon brake apply?, Ian Whelan, Wed, 3 Oct 2001 23:25:47 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Just what Justin says. Applying the brakes, or engaging the cruise control on a '86 or later car drops you into base boost. Base boost means the APC solenoid is disengaged. That click you hear is the solenoid disengaging.
There are a bunch of reasons for dropping to base boost with the brake pedal pushed, but biggest one is safety/liability. In the event of a stuck open throttle, a car has to be able to be stopped by the brakes. (yeah, I know you can shift out of gear...). If you've got full boost, the stopping distances will be greatly increased. As to liability, remember the Audi 5000 and 'unintentional acceleration'? Yes, that was the year after Saab introduced this feature, but I'll bet it was a good reason to stick with it.
Frankly, there is no reason to have full boost at the same time the brakes are applied. This feature may be disabled in rally cars, but for street driving, there is no need. You can keep the turbo spinning and still slow for a corner.
Boost is also reduced when the cruise control is on. I believe that this, too, is a safety feature. If the cruise control were to 'go nuts' and command full open throttle, the car would accelerate slower than if full boost was available, giving the driver more time to react.
Good luck!
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