How Does a Wastegate Work on a Diesel Engine Turbo?

We've talked a lot about turbochargers beforehow they work, problems you might have with them, and why you need one. But now we're focusing in on a different aspect of turbochargers: the wastegate.

We get a lot of questions on wastegates. You've probably heard the term before and now it's time to figure out what it actually does for your diesel engine! We'll go over why it's important and problems you might have when you alter the wastegate. 

Check out our video for a closer look at wastegates:



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How Turbochargers Work

As we discuss in How Diesel Engine Turbochargers Work, your turbo boosts power in your diesel engine. It does this by utilizing the exhaust gas from the engine. 

The exhaust gas travels through the turbine side and causes the components to spin. Air is drawn in and compressed into high pressure, high temperature air, which will then be forced through the outlet. 

By using this exhaust gas, the turbocharger brings more air into the combustion process, which increases your output. In turn, this boosts the horsepower of your engine without the need for increasing the size. It also increases the overall efficiency of your engine, so it's a double-win for you!


How a Wastegate Works in a Diesel Engine


how wastegate turbos work pneumatic actuator | Highway & Heavy Parts


So, now the nuts and bolts of how the wastegate works in your diesel turbo. The wastegate is going to be a pneumatic actuator that's attached to the exhaust housing. It has a line that runs to the compressor housing that senses boost pressure. 

As your boost pressure rises, the pressure in the sensing line increases and pushes against the springs and overcomes that spring pressure. It opens a valve inside the exhaust housing that lets some of the exhaust bypass the turbine wheel. (The turbine wheel is what gets spun by your exhaust manifold.)

So, essentially it's creating a leak in there to slow the turbo down.

The wastegated turbo is great because it's got a housing on the exhaust side that will spool that turbo up quick, but at the high rpm, when it's spinning fast, it's just too much for the compressor wheel. So, we need a wastegate to control the speed of the turbocharger.


Diesel Turbo Wastegate Calibration

The wastegates are calibrated based on pressure. That pressure is determined by the manufacturer of the turbo. They know that at a certain pressure, the turbo moves at a specific speed. If you overspeed the turbo, odds are the compressor wheel won't be able to handle it, and it will blow apart. 


Kinking Your Turbo Wastegate Hose


how wastegate turbos work crimped wastegate | Highway & Heavy Parts


We get a lot of turbos where we see guys that have taken vice grips and pinched off the wastegate hose, or used a zip tie and kinked it. 

Yes, that will boost pressure, but you run the risk of exploding the turbo from overspeed. It's just not designed to do that. Is that a risk you really want to take? 


Other Diesel Engine Turbo Problems

As you probably know, it's not just wastegates that can cause problems in your turbocharger. Among other things, you might also experience:

  • Plugged air cleaner
  • Excessive crankcase pressure
  • Drain line restriction
  • Valve guide seals or piston ring failure
  • Excessive crankcase pressure
  • Damaged compressor wheel
  • Damaged turbine wheel
  • Turbo bearing failure

That's not an exhaustive list of turbo failures, but it includes some of the common issues you might find. For more details on this, read Common Turbo Problems and Failures. Oftentimes, an issue with a turbo is caused by a failure somewhere else in your engine. It's important to diagnosis this larger problem to prevent your new turbo from failing as well.

If you're worried about failures in your turbocharger, you can take a look at our article on ways to keep your turbo healthy to learn things you can do to help prevent problems.


Overall, your wastegate is meant to help the turbocharger function correctly. It slows the turbo down to help prevent it from spinning too fast, causing a failure. So, don't discount the importance of this component in your diesel engine! 

Do you have more questions about turbo wastegates, or need help with your diesel engine parts needs? We have ASE Certified Technicians who can help! Call us at 844-304-7688, or request a quote online!