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a Manual Boost Controller is a simple little add on device that gives the used maual control over the amount of boost instead of it being computer controlled.
In your saab, the ecu uses the Boost Pressure control (located at thefront of the car, passenger side)to control boost. It is a solenoid valve with three hoses attached; one coming from the low pressure side of the turbo, one going to the Wastegate, and one to the the intake return pipe. The stock setup attempts to make the turbo very linear which in fact it is not. It also limits peak boost pressure to around 9-10 psi.
On a t-5 system, the MBC is used to bypass the BPC and hook the turbo up to the wg with the MBC in between them. The MBC is a simple ball and spring pressure relief valve that opens up when the set amount of pressure is reached. With an adjustable tension on the MBC, you can increase or decrease the amount of boost you want up to where the ecu sees too much boost and cuts the fuel, somewhere around 15.5 psi.
MBC's were originally a needle style bleed valve. While it increased your peak boost, it didn't do much for decreasing turbo lag. Then the gaited style or ball and spring style MBC came along and the turbo spooled up much more quickly. So this was a step forward.
The only drawback with ball and spring styles mbc's were that in colder temperatures, boost comes on so fast that the ball and spring react too late and it overshoots its set target. So folks would have to turn done their MBC to compensate for this overshoot. It you had a 3 psi overshoot, you would have to turn your MBC down to 12 psi to allow for the 3 psi overshoot. So this was a problem. The Dean gets this bright idea that if you can put an air pressure regulator in parrallel to the WG and supply the WG with some air to fill the line or prime it, when the MBC finally opens up, the WG can react quickly and not have an overshoot. Well it worked. So then, because the overshoots were taken care of, you can now effective more your boost source downstream of the IC and get better sustained boost at higher rpms for longer periods of time. So the MBC+A was born. It effectively deals with the inherant problem of boost overshoots and allows for moving the mbc pressure source to the throttle body for better sustained boost.
This is the shortened version. for the long version, do a search here on MBC+A or search for drs_anticipator on the 9-3 BB.
posted by 68.170.1...
, Fri, 29 Oct 2004 07:45:45
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