VNT Cleaning

If you are suffering intermittent lack of power then this could possibly be due to a jammed turbo VNT variable vane nozzle ring assembly.

The variable vane assembly in a turbo is used to control shaft speed and the turbo boost pressure required for the RPM and throttle position of your vehicle. The vanes work by directing the exhaust airflow through the exhaust wheel to increase shaft speed, then they open to allow air to pass around the exhaust wheel in order to either maintain shaft speed or reduce as required.

Due to the efficiency required and the accurate adjustment, the clearances in the variable vane nozzle ring are very small.

When an engine is started cold, the vehicle's ECU injects more fuel than that of a warm engine, this in turn means increased emissions and carbon. Carbon deposits cling to the internals of the exhaust housing, including the nozzle ring. If cold starts are common, like on short trips, or if the car is used on stop-start journeys, then the turbo will rarely get hot enough to burn off the carbon deposits. As the carbon continues to build up, the variable vanes start to jam on the carbon, locking them in position. Once jammed in position, the air-fuel ratio will no longer be correct, with the most common result being not enough air for the amount of fuel entering the engine. The result? Over-fuelling and MORE carbon build up!

If caught early enough, a good run on a motorway to get the engine nice and hot can cure the issue; but in many cases the engine ECU will continue to go into limp mode.


We can offer a cleaning service for this common problem to overcome this issue.

Simply send your turbocharger to us where we will strip and assess the unit. We will then strip the variable vane nozzle ring into individual component form and clean and polish before assembling and calibrating. The unit is then returned back to yourself. The cost? £80 plus VAT & delivery.

Sometimes a faulty turbo actuator could be your issue and the VNT is working fine. Should this be the case, we can repair or replace your turbo actuator to overcome your turbo problems.