Noob Q about boost controlers

[Templar]

Hello folks

What does a boost controller do and what's the physics behind it.

Thanks..

Simon

[baconbitz]

A boost controller is used to manage how much boost(psi) you want your car to produce. Its only useful if you have a turbo because that is what produces boost in the first place. As for the how it works, Ill leave that to someone with more indepth knowledge than me.

[gone_fishin]

The first step to understanding how a manual boost controller (MBC) works is to understand the function of the internal wastegate. After boost pressure builds and the turbo is no longer under load, it is the job of the internal wastegate to relieve the boost pressure. It is operated by an actuator, which pneumatically opens when a certain pressure is reached, and remains closed until that pressure is reached. The wastegate actuator operates by a base pressure spring (with a prescribed load). It's that prescribed load that allows for opening/closing at given pressures. This is how the wastegate maintains boost levels.

A manual boost controller cannot tell the turbo to make more boost than a turbo is capable of making wide open-- that is when the wastegate actuator is completely disconnected and all of the boost pressure is routed through the turbine. A manual boost controller is installed in line with the line leading to the pressure-side of the wastegate. When opened, it allows for diversion of the boost through it, essentially 'fooloing' the wastegate into allowing for more boost. Diverting 5 psi results in a 5 psi increase over un-tapped levels because it will now take an additional 5 lbs to open the wastegate. MBC's are very prone to boost spikes for two reasons: 1.) pressure builds easily if the BC lines are of narrow diameter, and 2.) pressure builds easily if the BC lines are too long. As is always the case, it's about finding balance between diameter and length for your application.