A turbocharger uses an internal or external wastegate to control the exhaust gases so that the turbocharger can maintain a certain amount of boost pressure.

Integral wastegate

With an internal or integral wastegate, the turbine housing of a turbocharger has a built-in flap that is opened and closed through the use of an actuator. The internals are most commonly found on vehicles that are turbocharged from the factory. When the set boost level is reached, the flap vents or redirects the exhaust gases so that they come out through the downcomer and thus try to maintain a constant boost level.

The actuator is normally being controlled by an electric boost solenoid that has vacuum lines that control it. GM part number # 1997152 is a popular option that has been adapted to work on many vehicles, whether domestic or foreign. Some OEM boost solenoids for Volvo, Audi, and others accomplish the same.

Typically, a vacuum line runs from the intake side of the engine or the turbocharger housing to provide the actual boost pressure that the engine is operating with. This line from the inlet to the first port on the solenoid sends positive pressure which is then bled into the solenoid to deliver this outlet pressure to the actuator. The actuator is basically a spring inside a container with a diaphragm that is controlled by the pressure that is sent to it from the solenoid.

With the solenoid off, the boost level is determined by the spring in the actuator cartridge. This is also known as the base boost, or the lowest boost setting the turbo can run. A modification to the actuator by placing a stiffer spring will increase the base thrust and is generally necessary if the vehicle has been modified to operate at a much higher thrust level than the original.

External wastegate

The external wastegate application is usually an aftermarket product that is not built into the turbocharger. Exterior location may vary based on application and fit issues. A full twin turbo kit for a 2005-2008 Corvette C6 has the turbos / dump gates mounted at the rear due to lack of space under the hood.

External discharge gates can be vented to atmosphere or redirected to vent through the exhaust system. When vented to the atmosphere, the noise produced is considerably high and may exceed legal noise limits, so make sure you are aware of the potential risks.

When the external relief valve is connected to the exhaust, the amount of noise is minimized and is similar to the noise level of an internal relief valve. Some people have mistaken a flush valve for a blow off valve and these are two completely different components that serve different purposes. The dump valve makes a sound that is more of a high-pitched, slightly high-pitched hiss. The external relief valve vented to atmosphere is much deeper and not as smooth. Typically, a small downcomer is connected to the discharge gate to direct the discharge away from anywhere that does not heat well.

Manual boost controllers

When you want to increase momentum, there are many devices on the market that claim to offer solid impulse control. Before we go and spend $ 500 or so on a fancy electronic boost controller, let’s first take a look at what’s going on.

As mentioned above with the integral relief valve, the actuator is used to hold the flap closed by using spring pressure. The preload must be set precisely or there will be a severe delay in the build boost or its setting too tight can cause a boost spike and damage a motor. It is extremely important to set the preload correctly, whether you are running stocks or higher momentum levels.

A simple but extremely effective $ 45 boost controller can provide excellent boost control. The boost valve is a product that has proven its reliability for years and offers additional springs to allow for higher boost settings.

Maintenance

Integral discharge gates can become sticky, where the tailgate flap gets stuck or simply does not swing freely. This is an important inspection that could cost you a lot of performance. If the flap does not open and close smoothly, it may hang, causing a delay in building momentum or spikes in momentum to overcome where it hangs. A GM product called a heat riser lubricant can be injected to help loosen the fin.

The vacuum lines leading to the boost solenoid may need to be inspected depending on the condition or age of the vehicle. Replacement silicone vacuum lines are usually a good option.

The last suggestion is to take a close look at your data log files to see how stable your boost control is, whether it is increasing or decreasing. A properly configured wastegate can make all the difference in terms of overall turbo engine performance, and you may only need to make a few small adjustments to see dramatic performance improvements.