Manual boost controllers are as old as the technology of turbocharging but every bit as useful as they were in Day 1. What the manual boost controller is comprised of is a basic ball and spring valve that is actuated once the pressure of the turbo exceeds the pressure of the spring.

Once this point is reached, the boost will “bleed” off from the valve and actuate the internal or external wastegate, therefore controlling the boost pressure entering the engine.

Today we’ll be showing you how to build your own manual boost controller (MBC) and showing you How To Build a MBC.

Before continuing our How To Build a MBC guide, please make sure you are comfortable working on your own turbocharged vehicle, and that you own a boost gauge. Improper installation or adjustment of this variable can cause catastrophic engine failure before you know it.

Never attempt to raise your car’s boost threshold or adjust the tuning factors of your vehicle or ECU if you are not comfortable with what you are doing. Do not install this homemade MBC into anyone else’s car without their consent, and NEVER install a boost controller without a boost gauge.

How to Build a MBC

Most of these parts can be found at your local hardware store, or at mcmaster-carr for pennies on the dollar. This entire setup as shown cost us a grand total of 9.80 cents from the store and took just a few minutes to assemble.

The magic fitting size here will be 8th inch NPT, a common thread pitch in many fuel or boost related components. The only component we recommend you getting more than one of is the spring.

Because this spring rate is what your boost controller is based on, it may take some time in trial and error before you find a spring response that works for you. More pressure on the ball and spring, the more pressure you will be able to raise your turbocharger to.

When upping the boost in your vehicle, make sure you understand what the common fail point is for the gas you are using. For example if you live in California and are restricted to 91 octane, it might not be a good idea to raise boost to the same levels as others may use with different gas.

Stock internals can only take so much without the proper fuel and tuning adjustments. Make sure you are aware of these limitations for your vehicle in question and never exceed the boost pressures recommended.

When you have your homemade MBC assembled with teflon tape and tightened together, it’s time to install it by following the diagram above. Make sure to install the bottom port of the MBC to raw pressure of your turbocharged system and that the side port leads to the wastegate actuator nipple or boost control solenoid.

That does it for our How To Build a MBC Guide for DIY and shadetree garage mechanics. This modification has been tested on many different turbos and vehicles, and has propelled many of our own vehicles well into the 400 hp range on our 448x Dynojet chassis dynamometer.

Have any questions for us? Leave them below!