All About Turbochargers – Part 6: Boost Controllers

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The greatest thing about a turbocharger is the ability to change how much boost will come into an engine by a twist of a knob or the push of a button. You can even get brave with over-boosting. Yes, that is a real thing! Let’s talk boost controllers.

Boost controllers might seem like magic, but the way they work is actually very simple. Inside the wastegate is a metal spring and a rubber or neoprene diaphragm. The pressure side of the wastegate housing has a nipple (or a provision to install one) that will have a hose connected to it. In normal circumstances, it connects to the intake manifold looking for boost to feed into the wastegate. Once the right amount of boosted air is in the wastegate, it forces the diaphragm to push on the spring in the wastegate and opens the valve to bleed off exhaust gases away from the turbo’s turbine.

Here is where a boost controller comes in. We’ll start with the manual boost controller first. It’s essentially an interrupter between the manifold boost pressure and the wastegate. There are two nipples on the boost controller; one comes from the manifold while the other leads to the wastegate. Inside the controller is typically a ball and spring.

boost controller 5
In much the same way the blow-off valve works, boost pressure will ride on the ball until it overcomes spring pressure to open it and allow boosted air into the wastegate. However, you can adjust this with a twist of a knob on the controller, adding tension to the spring and making it harder to open. Slowly adjust this until you reach your desired boost pressure and set it.

An electronic boost controller is doing essentially the same thing. However, instead of relying on a ball valve and spring pressure, it relies on a boost pressure sensor and a solenoid.

The solenoid is a magnetic switch. When you apply current, it charges a coil to move a valve in the case of boost controllers. With it you get electronic accuracy and will set it to boost pressure without the need to slowly screw the controller like on the manual boost controller. Electronic boost controllers range in abilities from simple boost controlling to staged controlling (where you can set boost for speed, rpm, gear, nitrous, etc.) to being able to over-boost.

Over-boost is a real thing, not just some video-game-created power-up. It is used to create a higher maximum boost pressure than you normally use. That doesn’t necessarily mean using it will blow the turbo or trigger an engine meltdown, though, if you’re brave or stupid enough, you could set it at that point. It can be your “OH SHIT” button, your “I need more torque” button, or it can be your “I’m really this stupid and will blow my engine” button. The choice on that one is yours to make.

If you do boost for a long time or use your over-boost in a stupid manner, you’ll need to look into another device: the turbo timer. It will keep your engine running for a short period of time after the car has been turned off. This allows hot oil to continue to circulate in the engine and turbo. Gradually cooling the compressor after hard driving will keep your oil from gunking up and will prolong the life of your turbo. If you’re worried about theft while it’s running, don’t be. Many can be programmed to turn off the engine if the ignition lock cylinder is in the off position and you touch the brake or clutch pedal.

Next, we look into a critical area in helping you choose the right turbo for you: turbo compressor maps.


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