A manual boost controller (MBC) is one of the first modifications done on the turboed DSM’s. This is the reason I decided to do this write up.
What does a manual boost controller do? Easy. It allows you to raise the boost. Doing this can give you a lot more power by increasing the boost but could also cause catastrophic failures if you raise the boost too much and do not have the mods to support it. Installing a MBC will delete the previous existing boost control solenoid (BCS).
If you have little too no mods when installing a MBC, you should only raise the boost a couple pounds from where you run with the stock boost control solenoid. If your car is basically stock, you should be running around 10-11psi. The highest amount of SAFE boost you can run with no mods and only a MBC is 16lbs. No more than 16lbs.
It is important that you install an aftermarket boost gauge before ANY mods. You need to be able to read your boost pressure accurately. Your stock boost gauge is far from accurate. Especially when not running stock boost pressure.
Once you have installed an aftermarket boost gauge and have purchased a MBC, you are ready to install it. The only tool you may need to use is a set of pliers if working with any hose clamps.
Step 1: Pull Out Boost Control Solenoid
Your MBC will replace the boost control solenoid. Thus, you need to take it out. Take notice where each of the vacuum lines ran to and how they were connected to the BCS. Do not discard the vacuum lines as you will need them for use on the MBC.
Step 2: Vacuum Lines
There are (2) vacuum lines that need to be connected to the MBC. One will go from the vertical nipple on the MBC, to the J- pipe. The other will go from the horizontal nipple on the MBC to the wastegate actuator. You may need to shorten the vacuum lines a bit. The shorter the vacuum lines are, the quicker the boost response. Before you start shortening the vacuum lines, figure out where you plan to mount the MBC. This should be the exact same way the vacuum lines were ran on your BCS. Here is a diagram I made to show exactly how the vacuum lines need to be ran.
Here are a couple of actual pics of where each vacuum line goes to. First pic is where the vacuum line on the vertical nipple connects to the J- pipe.
This pic is where the vacuum line on the horizontal nipple connects to. It connects to the nipple on the wastegate actuator.
Step 3: Mounting the MBC
You want to mount the MBC so that it is secure and does not move around very much. This will be entirely up to do. The possibilities are endless and everybody mounts their MBC differently. You could zip tie the MBC in place until you decide on how you want to mount it. The most important thing is that the MBC is secure. Mounting is just for looks really. You can get real creative and fancy with it. So have fun.
NOTE: AFTER INSTALLING THE MBC, PLEASE MAKE SURE THE KNOB IS AS LOW AS IT CAN GO. THIS WAY YOU DON’T OVER BOOST AND CAN ADJUST IT TO YOUR LIKING AS YOU GO.
How a MBC Works
A MBC uses a ball and spring to change the compression and is able to be changed with the knob. If you tighten the knob, it will increase the compression and raise boost. Loosening the knob will lower the compression and you will run lower boost. The air travelling though the MBC forces the ball upwards so the air can go out. Think of the ball as a door. The spring holds the door shut. So depending on how much pressure is already on the spring (based on your adjustment with the knob), the ball is going to need a little bit more pressure than that exact amount of pressure to be pushed the opposite way. Once the boost overcomes the spring pressure, it enters the chamber and goes to the wastegate actuator which then opens or closes more/less. Kind of like a signal. The amount of boost that was needed to push the ball in the MBC and force the spring back , that same amount of boost goes to the wastegate actuator.
To better explain this, here is another diagram I made.