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Wastegate Springs & How to Choose the Right Spring (Complete Guide)

Updated: 1 day ago

Choosing the proper wastegate spring may help you get the quickest turbo spool up and boost pressure stability with the least amount of high-RPM boost pressure drop-off.


You must always re-adjust your boost control settings after replacing the wastegate springs. This is simple to perform if you have a manual or electronic boost controller, but if your ECU controls boost you will have to have it reprogrammed to accommodate the new wastegate spring. 


The focus of this article will be on turbo systems that include use a pneumatic wastegate that is coupled to a boost control system that activates the wastegate using boost pressure.

 

Table of Contents:


wastegate and different sized wastegate springs

Gate Pressure

The boost pressure that your turbo system reaches without the assistance of a boost controller is known as "gate pressure".


The spring in the wastegate has a direct influence on the gate pressure. The wastegate spring determines the amount of boost pressure that is required to open the wastegate valve and allow exhaust gases to bypass the turbine.


  • If the spring is too weak, the wastegate may open too soon, resulting in lower boost pressure and reduced engine performance.

  • If the spring is too strong, the wastegate may not open until the boost pressure is too high, causing an overboosting situation.


But keep in mind that even though wastegate springs normally feature a boost pressure "rating", this is merely a suggestion. Due to the number of factors affecting the turbo and wastegate system, it is difficult to predict the precise gate pressure that a given spring will accomplish.


What Does a Wastegate Spring Do?

A wastegate spring is a small spring that is used to regulate the flow of exhaust gases through the wastegate valve in a turbocharged engine.


The spring is mounted inside the wastegate actuator and it is responsible for determining the amount of boost pressure that is required to open the wastegate valve.


When the boost pressure reaches a certain level, the wastegate valve begins to open, allowing some of the exhaust gases to bypass the turbine and reduce the amount of boost pressure being generated.


The wastegate spring plays a crucial role in determining the point at which the wastegate valve begins to open.


The wastegate spring is typically rated by its spring rate, which is the amount of force required to compress the spring. A higher spring rate means that more force is required to compress the spring, and as a result, the wastegate will open at a higher boost pressure.


On the other hand, a lower spring rate means that less force is required to compress the spring, and the wastegate will open at a lower boost pressure.


The wastegate spring determines the amount of boost pressure that is required to open the wastegate valve, which in turn helps to regulate boost pressure and prevent the turbo from over-speeding.


It is important to select the appropriate wastegate spring for your specific turbo system in order to achieve optimal boost pressure and engine performance.


How to Choose a Wastegate Spring

The wastegate spring plays a crucial role in determining the amount of boost pressure that is required to open the wastegate valve, and it can have a significant impact on engine performance and the overall functioning of the turbo system.


In this section, we will provide some tips on how to choose the right wastegate spring for your specific turbo system.


By understanding the various factors that influence the selection of a wastegate spring and the proper methods for determining the appropriate spring rate, you can ensure that your turbo system is operating at its best.


When choosing a wastegate spring, it is important to consider the following factors.


  • Boost pressure: The desired boost pressure will help to determine the appropriate spring rate. A higher boost pressure will typically require a stronger wastegate spring, while a lower boost pressure will require a weaker spring.

  • Turbo size: The size of the turbo will also influence the appropriate spring rate. A larger turbo will typically require a stronger spring in order to achieve the desired boost pressure.

  • Engine displacement: The engine displacement will also play a role in determining the appropriate spring rate. A larger engine will typically require a stronger spring in order to achieve the desired boost pressure.


Boost Pressure Shouldn't Exceed Twice the Gate Pressure

The wastegate in a pneumatic turbo system is a self-regulating valve that uses boost pressure as a feedback loop to control boost. The spring in the wastegate determines the point at which boost pressure becomes stable, also known as the "gate pressure".


A boost controller works by altering the amount of pressure in the boost reference hose to the wastegate, raising the boost pressure at which the "equilibrium" point is reached.


However, there is a limit to how much the boost controller can influence the wastegate, as the boost reference signal must be sufficient to effectively regulate boost.


When boost pressure exceeds double the gate pressure, external variables that affect boost production can no longer be effectively compensated for, leading to unstable boost control and potentially reduced performance.


Variable Boost Settings

If you plan to use multiple or variable boost settings, it is important to select a wastegate spring that is appropriate for your lowest boost setting.


This ensures that the wastegate's "gate pressure" is aligned with your lowest boost setting, and it helps to ensure that your highest boost setting does not exceed double the lowest setting.


In some cases, it may not be possible to achieve this balance, and you may need to make a compromise.


You can either choose to keep the low boost setting where it is and sacrifice some performance at the high boost setting, or you can increase the low boost setting with a stiffer wastegate spring and optimize the high boost setting for performance.


Ultimately, the best option will depend on your specific needs and goals for the turbo system.


Are Wastegate Springs Universal?

Wastegate springs are not universal and are specific to the wastegate and turbo system that they are used in. Different wastegate springs have different spring rates, which determines the amount of boost pressure required to open the wastegate valve.