Published by Tim Scott on Jun 3, 2016

In this video, we will introduce a variety of turbocharger controls including wastegate setups, actuators (including vacuum controls, boost controls and dual port), and electronic solenoid controls. We also show how a malfunction can cause low boost pressure and power loss.

Part 2 of this video (click here) will discuss wastegates, actuators, and how they are used to control turbo rotor speed.


Hey everyone. I just want to say thanks for coming back to Tim’s Turbos Information Center.

What I want to do is go over wastegate setup, actuator control, and some electronic solenoid controls.

I’m going to make this a two-part video, because they seem to be getting a little too long.

So I want to talk about actuators that are controlled by a vacuum, ones that are controlled by boost, dual port actuators, wastegate setups, what they do to your rotor speed, and then we’re going to go over the solenoid that you see on most cars today.

So first off I’m going to start out with the solenoids.

On a typical 2.0 Audi, this is basically the setup everybody’s running these days.

Solenoid Setup on a Typical Audi

You’re going to get a boost reference point from the compressor.

Solenoid - Boost Reference Point from the Compressor

Now this is the inlet side, so this is what is going to be actually hooked up to the air filter over here.

The Inlet Side of the Solenoid

This is the boost pressure outlet.

This is the Boost Pressure Outlet on a Solenoid

This signal line is going to give in to the actuator, so it’s going to be its reference port.

When your boost pressure comes up into here, it is going to fill this solenoid and this valve is usually set in a closed position, so it’s not bleeding off the boost pressure into the tube. What its doing is its going into an L-shape connecting over to your actuator.

Example of an Actuator That is Connected to the Wastegate

This is your actuator that is connected to the wastegate. From here to there, you’re going to have your signal line. Whatever spring pressure that your actuator is set at is going to be the lowest boost pressure this vehicle can do.

To make the math simple, if this is a 10 pound spring in here and your compressor is putting out 10 pounds of boost, its going to open up that actuator and give it its lowest level of boost possible. The only way that it is going to raise the boost pressure by holding the rod in here longer is when the computer gives a false signal to the actuator.

What that does is it actually bleeds off the extra pressure, so it could have 20 pounds of boost in there and it will still only show that it has 8 or 9 pounds of boost here, so it will hold the boost pressure and the wastegate closed, bringing up your rotor speed.

Once the rotor speed is picked up, the actuator opens, closes, goes back and forth, cycles many, many times over. So if you have a default position with a low boost code, if this piece is broken, then no matter what you do you’re pretty much only going to get the lowest level of boost because you’re actually giving a full signal of boost to the actuator. I know it sounds a little confusing, but that’s kind of the way it works.

So now that I’ve explained a little bit about electronics, I’ll go over in part 2 what the actuator in comparison to the wastegate and rotor speed does. I’ll see you in a minute.