Boost Controllers

hey
how do boost controller's work?
and are they even necessary??
i thought the stiffness of the spring in the wastegate affects how much boost you're running...??

hey
how do boost controller's work?
and are they even necessary??
i thought the stiffness of the spring in the wastegate affects how much boost you're running...??

It does, but a boost controller(bc) sort of tricks the wastegate(wg). The bc builds up pressure before the wg even knows that it's there. It's kind of like taking a fire hose and connecting it to a garden hose. The connection between the fire hose and garden hose would be the bc. It is holding back the amount of water in the fire hose and only letting through the amount that can go through the garden hose. The end of the garden hose would be the wg. It's not exactly like this, because first off, the hose from the turbo to the bc is the same size as the hose from the bc to the wg, but you see my point. The bc holds, say 18psi, meanwhile it is letting air through to the wg so it is still bleeding off what it is set at, say 14psi.
I'm not doing a very good job of explaining this, but to say if they are necessary or not is up to you. If you don't plan on turning up whatever the boost is set at on your wg, then no they aren't. Most people do though so for most, they are a necessity.

Yeah, thats close... an easier explanation - Yes a wastegate's spring determines when it opens. Boost pressure pushes against the spring, as the pressure builds, the wastegate opens more and more until it reaches a point where boost levels off. A boost controller blocks the passage of boost pressure from ever getting to the wastegate until the desired boost pressure is achieved. This gets you two advantages over just running a wastegate:
1. Wastegates when hooked directly to the turbo/manifold will open slowly as boost pressure rises. This causes the turbo to spool slower. With a boost controller, the wastegate stays closed until the desired boost is achieved.
2. Boost controllers allow you to run more boost. It will keep the wastegate closed regardless of the pressure the wastegate usually requires. There is one catch though - if you increase boost pressure too much(like 20+psi, depending on the wastegate- slightly above 20 is typical for stock IHI RB5 and Garrett t3 wastegates) the extremely high exhaust pressure will force the wastegate open even without any boost pressure. You can get around this with a twin port solenoid valve and a vacuum canister, or using an aftermarket wastegate that has a stronger spring.

One disadvantage - pressure spikes. Since a boost controller cannot open instantaneously, and since boost pressure cannot move from the controller to the wastegate instantaneously, the wastegate will remain closed for a fraction of a second after the controller opens. This will cause the turbo to keep spooling after the desired boost is achieved, making more pressure until the wastegate gets the boost signal and opens. This is called a pressure spike. If you have tuned your engine very close to the threshold of detonation without a boost controller, back off the timing a bit when you put one on. If you hit a pressure spike, the slight overboost may cause your engine to detonate. Detonation is not good, it will burn holes in your pistons.