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The BPC is supposed to buzz Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Thu, 19 Jan 2006 05:21:10 In Reply to: BPC solenoid buzzing is not a sign of failure, right?, AlexA, Tue, 17 Jan 2006 15:42:20 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The BPC is an electrically controlled valve. There are two electrical coils there to position the valve. The way it works is that one coil pulls the valve open, the other pulls it closed. The ECU sends electrical pulses to both coils at around 75-90 hertz (a low buzz to your ears). When the pulses are the same width, both coils pull the same amount, and the valve stays where it is. If the ECU wants to move the valve, it makes the pulses to one of the coils wider, and narrower to the other coil. So one coil is now pulling stronger, and the valve moves. The frequency of the buzzing doesn't change - just the width of the pulses. You hear the pulses, but not the width change. This causes the valve to vibrate some.
The ECU actually changes the frequency slightly depending on engine speed to keep from interacting with some resonant frequencies in the intake plumbing.
Hearing the buzz is normal whenever the engine is running. However, if the buzz is very loud or noticeable, as others have pointed out, it could be the sign of a loose mount. Only you can know what's normal for your car. But the BPC is supposed to buzz.
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