Seized VNT

So you think you have a seized VNT ? But what is it exactly ? VNT stands for Variable Nozzle Turbine.

The internal technology of the turbocharger uses variable vanes to control the exhaust flow against the turbine blades. Its able to vary the flow as required.

At low engine speed, the vanes are in the “closed” position narrowing the gap between them which accelerates the exhaust gas onto the turbine wheel. This provides good response and characteristics at low rpm.

As the engine speed increase the vanes open allowing greater flow of gas through them.

In other words a VNT turbo is a variable turbo, acting like a small unit at low rpm giving good response and performance and then becoming a larger turbo as the engine requires more flow and boost.

The VNT mechanism exists in a very difficult environment and many drivers have some unrealistic expectations when the vanes come to the end of their lives. They are NOT lubricated and operate directly into the flow of exhaust gases which can exceed 600 degrees.

Every time you touch your throttle the VNT mechanism moves – just think about it for a moment. Millions of time the VNT mechanism will move during a typical life time. Eventually they wear out and combined with soot etc start to malfunction.

So Can A VNT Be Fixed ?

Seized VNT is with doubt one of the most common issues we come across. Some of the time soot build up can cause this issue however in most its simple wear and tear. When the cause is carbon related then we would tackle this with our class leading Hydroflow decarbonisation treatment.

Check the following video out first showing the operation of a seized vnt mechanism causing over boosting issues on a Volvo and the mechanism itself. You will see a stiff seized mechanism and how the vanes should operate.