Electronic Boost Controller Before we examine how a boost controller works, we need to understand how the turbocharger would control boost levels without a boost controller. A turbocharger has a component called a wastegate, which is a like a valve. When the valve is closed, exhaust gasses pass through the turbine side of the turbocharger, causing it to spin and to compress air in the compressor side of the turbocharger. When the wastegate valve is open, exhaust gasses pass through the wastegate bypassing the turbocharger turbine. When this happens, the turbine slows down and the boost level begins to drop. The wastegate is opened and closed by the wastegate actuator. The wastegate actuator is connected via a vacuum line to the compressor side of the turbocharger. As boost levels increase, pressure inside the wastegate actuator also increases, pushing against a diaphragm. As this diaphragm moves, it moves a rod, which is connected to the wastegate actuator, which opens the valve and releases exhaust gases away from the turbine wheel. The best way to control a turbocharger's boost is an electronic boost controller. These devices are small computers that typically use an electronic pressure sensor and a solenoid valve. The pressure sensor constantly reads the current boost pressure in the manifold, while the solenoid gets connected between the manifold and the wastegate actuator. The computer can be set to open the solenoid valve at any pressure you desire. In most electronic boost controllers, there is a plethora of features to make the boost come on, and be cut off, in most any fashion you desire. In addition, electronic pressure sensors are quite accurate, making the system highly controllable and safe for the engine. Electronic boost controllers therefore allow the driver to instantly increase the amount of boost the turbo is producing over stock levels. This allows for a simple and safe method of extracting more power.