OK. A waste gate is acts like a door. When the pressure in the exhaust pressure in the exhaust manifold reaches a certain point, the wastegate opens releasing the exhaust gas via a little latch like the ones that stock on our cars. This dosen't allow the exhaust gas to spin the the turbo becasue it never reaches the turbo, thus controlling boost. So when the wastegate is closed, the exhaust is entering the turbo, spinning it. When the wastegate is open, the exhaust gas is bypassing the turbo by going into the wastegate opening.
Our stock and external wastegate use springs to regulate boost. The spring is located inside the wastegate. The springs rates determine when the wastegate will open at a certain amount of boost. For example, a 14psi spring will hold boost till 14 psi then open the waste gate and so on. Usually a boost controller is used in conjunction with a waste gate to hold even more boost. When a Boost controller is used, the wastegate will act like a fail safe.
Im not to sure on the adjustable ones this is wat I think. On the adjustable wastegates, like the ones where u adjust the rod, the rod is adjusted so it preloads the spring but at the sametime it dosen't open the wastegate latch in the manifold. By preloading the spring, it will take more boost to compress the spring and open the latch later. Thus allowing you to make more boost.
Boost is read from the intake side via the vacuum fitting on the wastegate. As the car boost, the pressure will build up. When the pressure on the intake side is greater then the pressure of the spring, the wastegate will open. I added a pic to help you understand:
so what and how does the WGA open the WG, from the exhaust pressure or intake pressure?
both, but to keep it basic, the exhaust pressure. but while were on the topic why dosent some one explain how a BC works to keep the WG shut (i suck at explaing this stuff).
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A boost controller acts just like a wastegate. It is an open and shut valve. It works by preventing vacuum from reaching the wastegate. If the wastegate has no vacuum, it won't open to release pressure allowing you to reach higher boost levels.
Manual boost controllers works exactly like a wastegate. The are installed on the vacuum line between the wastegate and intake. The use a spring and a small ballbearing to hold boost. Just like an adjustable wastegate, you can adjust the preload of the spring inside the the boost controller to controll boost. Boost controllers are set at higher boost levels then the wastegate. For example, a stock wastegate holds only 14 psi. You set the boost the contoller to 17 psi. Your car will now boost to 17 psi via the boost controller. If you go over 17 psi, the boost controller will open, allowing vacuum to reach the wastegate, since the wastegate is only can only hold 14 psi, it will automatically open, droping boost to from 17 psi to 14 psi.
Electronic boost controllers work the same way, except they are usually more safer. Instead of vacuum, electronic boost controllers use boost sensors to open and shut their valves. You also get better controll over boost with electronic boost controllers.
A wastegate has to be used. The boost contoller only modifies the vacuum signal going to the wastegate. The wastegate is what actually controlls boost by physically opening and closing the wastegate opening, expelling exhaust pressure.
a few years back, i stuck a boost controller on my line going to the stock WG and it didn't work too well at all. Found it easier just going w/ wastegate control.
A wastegate has to be used. The boost contoller only modifies the vacuum signal going to the wastegate. The wastegate is what actually controlls boost by physically opening and closing the wastegate opening, expelling exhaust pressure.
I thought it prevents vacuum from going to the wastegate, which is it? does it prevent the vacuum from reaching there or modify the vacuum going there
It stops the vacuum from reaching the wastegate. I just used the term "modifies" because u can adjust boost settings. A wastegate needs pressure to open and close its opening. Without a source of vacuum, the wastegate will not open and you'll over boost. A boost controller stops vacuum flow until a given point, then releases so that the wastegate can receive the vacuum and open, releasing exhaust gas.
Manual boost controllers have a reputation for losing their boost settings and often failing. Even the expensive ones sometimes fail. An electronic boost controller is better because the valve is controlled electronically making it less prone to failure.
Last edited by Madisonr34 : 10-01-2008 at 03:16 PM.
Heres a picture of the stock wastegate, that big thing connected to your turbo isn't the wastegate, just the wastegate actuator. That door is the actual wastegate which opens and closes via the WGA arm which is in turn controlled by boost pressure.
Thats an internal wastegate. An external one is the same but routes it to the atmosphere instead of back into the exhaust right before the o2.
Here it is from another angle, different turbofold but still the same thing
You can kind of see the hole in there which opens and closes via the WGA arm.
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how a Wastegate works
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