[Raid3n]

Dial-A-Boost ( Manual Boost Controller or VBC ) Installation Diagrams

The first thing to do when working with a manual boost controller is to understand how it works. First, a VBC cannot raise the boost level higher than the Turbo is capable of making with the wastegate actuator disconnected. In other words, if your turbo only makes 12 psi wide open, a VBC will not allow it to go to 14 psi. Second, a VBC is nothing more than a controlled boost leak ,albeit a fairly accurate one. The way a VBC works is&

Your external wastegate or internal wastegate actuator has a base spring setting. For the sake of description lets say it has a 5 psi spring. That means that when 5 psi boost hits the diaphragm the wastegate opens. The VBC is installed inline with the hose that leads to the pressure side of the wastegate and the other side of the VBC is a vent. When the VBC is in the closed ( You cannot blow through it ) position, all the boost pressure goes to the wastegate and you have a stock boost level. As you open the VBC boost pressure that would have gone to the wastegate now diverts through the VBC. What this does is fool the wastegate. If you bleed off 5 psi on a 5 psi system it will take 10 psi to open the wastegate resulting in a 5 psi boost increase on your boost gauge and a lot more power from the engine. This is the simple version and results vary with the system, the size of the hose being used, the sensitivity of the wastegate spring. Manual boost controllers are also very prone to boost spikes. This occurs when the VBC is open all the way and small diameter hose is being used. The boost pressure builds faster than the hose can flow which lets the turbo spike up big boost numbers until the pressure fights its way through the small hose to the diaphragm, then the boost drops back down. This is a dangerous situation since the spike can blow up your engine before you know what happened. The best way to minimize spike is to keep the manual boost controller located under the hood with as short a length of hose as is possible. This is easily demonstrated by you picking up a piece of ¼" hose 4 feet long and trying to breath through it. Go ahead, try it. Pretty tough isn't it. Now cut the hose in half and try it. Much easier. Your turbo and wastegate feels the same way.



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