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Re: What is a MBC? n/m.
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Posted by SteveB (more from SteveB) on Tue, 25 Jun 2002 09:39:31 Share Post by Email
In Reply to: What is a MBC? n/m., Sean, Tue, 25 Jun 2002 09:30:02
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Others could explain it better, but here's my version.

MBC = Manual Boost Control

From the factory, the boost is controlled by the ECU. When the ECU decides to limit boost, it opens the wastegate by opening a valve that applies boost pressure to the wastgate actuator. As I understand it, SAAB decided to limit boost in 1st & 2nd gear, and generally taper the boost to provide a linear torque curve.

The MBC is simply a spring loaded check valve that bypasses the ECU controlled valve (name anyone ?). The MBC stays closed until the preset pressure is reached, then the check valve opens and allows pressure to the wastgate actuator, which opens and reduces boost.

Since the MBC remains closed until max pressure is reached (as opposed to opening and closing per instructions from the ECU) the turbo spools up quicker, and max boost is possible in all gears.

Anyone who wants to refine this explanation is more than welcome to...

posted by 67.98....

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