Boost Control Overview

My three port MAC valves showed up today. These are centerpiece of my boost control strategy for this build. I will be utilizing a two solenoid method of boost control.


One solenoid will be a fill solenoid, the other will be a dump. They will both be controlled via the MS3x ECU. This method responds very quickly to demanded adjustments for boost level. The fill solenoid sits on one end of a T setup. The inlet is fed via compressed air or CO2. My setup will be using onboard air. One of the outlets is connected to one side of the T. The other outlet is plugged. The dump solenoid’s inlet is connected to the opposite end of the T fitting. One of the outlets is plugged, the other is fitted with a filtered vent fitting. The remaining fitting on the T fitting goes to both wastegates. It branches out to the top of each wastegate.

The bottom ports of each wastegate goes to the fitting on the compressor housing.

One of the wastegates has a pressure transducer mounted in the upper ports to monitor air pressure on top of the wastegate. This is how the ECU sees what pressure is on top of the gate and base it’s adjustments on. So for instance lets say you commanded 25psi of air on top of the gates. The fill solenoid will open using pulse width modulation and pressurize the top of the wastegates. Once the ECU using the pressure sensor sees 25psi, it starts to open the dump solenoid using pulse width modulation to maintain that commanded 25psi.

This method, though more complex due to requiring more components and not always supported by all ECUs, is superior due to being more responsive and more precise in it’s ability to maintain proper boost levels. This is due significantly to not relying on a single solenoid to increase AND decrease pressure like in a typical ‘bleed’ setup using a single three or four port solenoid. .

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