Yeah I´m not putting my life on my pencil pushing, but I am putting my EGT on it, and she´s my baby.
Yeah, James´ explanation is pretty close.
Turbo uses energy from exhaust gas to spin. As it spins it compresses air. More air in the motor, more air out of the motor creates a higher Volumetric Efficiency and gives you more power. (Honestly think of it as Artificial Cubic Inches
) The Wastegate itself you can be set up different ways, most common is when you hit a preset boost level it opens. When it opens it lets exhaust bypass the turbine. So basically you´re controlling the speed of the turbine which controls the speed of the compressor, hence holding boost levels constant.
For myself right now, my problem is tuning. When I boost my motor with 4 or 5psi the car falls on its face. All indications show I´m running lean and simply running out of fuel, but with the new fuel computer in, the same problem is happening. I live in a little town and all the people I know that claim to know everything about forced induction, can´t seem to help me. So I spend everyday looking for answers. The only reason why I know so much is because I´ve had to learn so much to still not understand all the problems I´m having. But I assure you, I´m the only person I know that can screw up just about anything. And I have TERRIBLE luck. I´ve never been good at anything in life either....so if you´re planning on turbo´ing your EGT, you´ll more then likely have better luck with not knowing nearly as much.
Boost Controllers: Well here´s how it works (most of the time). Most of the time its a simple one-way valve that cuts the amount of airflow from the pressure side of the turbo to the wastegate actuator. Wastegate actuators are usually diaphrams with a spring. When the right amount of pressure is asserted it moves a rod, that rod opens the wastegate. The simple one way vavles you can make with Home Depot parts and will allow you to raise your boost level over the base setting of the wastegate actuator. Some get really advanced like the A´PEXi AVC-R (Actuator Valve Controller, Type-R). Its electronic and uses a pop-valve to open the pressure at just the right time to maximize your boost level and ability to hold boost on a non ballbearing turbo. It can do other things like look at your pulse width of your injectors, so if one locks up it stop boosting your motor. And it has a scramble mode that will just give your motor as much boost as your turbo can produce. HKS makes the Profec-B, another highly recommended boost controller. Same idea as the A´PEXi, just easier to use but the display isn´t as cool.
In all honesty its not hard to turbo a car and not know a thing about boost. To understand it really is facinating I recommend you read into it. You can learn everything from the physics and chemistry of combustion, to having a better understanding of your environment and why there is no "perfect" answer to everything.
