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Boost Control: Boost Control Solenoid Operation

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Boost Control Solenoid Operation


00:00 - Before we move on, there are a couple of aspects of the solenoid's operation that are worth discussing in a little detail.
00:08 The first is the operating frequency or how many cycles per second the solenoid will happily work at.
00:15 If you drive the solenoid at a frequency that's too slow, the boost will tend to oscillate up and down slightly at the frequency of the solenoid.
00:24 And this may be accompanied by an audible pulsing of the boost pressure.
00:29 This obviously isn't desirable and a higher frequency can help eliminate this.
00:35 If you raise the frequency too high, though, the solenoid won't have enough time to operate properly and it won't work at all.
00:42 - Somewhere in between is a happy median and most boost solenoids will operate well with a frequency of 15 to 20 hertz.
00:51 Along with the frequency, there's also a dead band at the high end and low end of the operating duty cycle where the valve essentially won't function.
01:00 I'll explain this a little more thoroughly.
01:03 For a popular valve, such as the MAC solenoid, for example, if you provide it with a duty cycle of five percent, the valve won't operate.
01:11 It's as if the duty cycle is still zero and the valve remains closed.
01:16 It's not until you get past about 12 to 15 percent duty cycle, that the valve will start operating normally.
01:24 Likewise, at the high end of the duty cycle, you'll find that anything higher than about 85 to 90 percent, will end up having the valve fully open.
01:33 So, for the mech valve, the useful range where we actually have control over the boost pressure is approximately 12 to 88 percent.
01:42 It's important to understand this as it will influence the values we can use in our boost control tuning once we start setting up the system.