Diesel VGT Turbo Service and Maintenance | AG Auto

Diesel technology has slowly but surely seen great advancements in its technology over the years, but one thing is for sure; electronically controlled variable geometry turbochargers (VGT) are now an industry standard in heavy and medium duty diesel engines. VGT turbochargers have risen in popularity due to their versatility across different applications while boosting a diesel engine’s performance capabilities. 


Don’t question the performance or reliability of your diesel vehicle and have one of our experts at AG Automotive service your variable geometry turbocharger so you can get back on the road with confidence.  


What is a VGT turbo?


Variable geometry turbochargers have become standard in direct injection diesel engine vehicles across various industries, as well as in personal vehicles for the following reasons:

  • Increased engine acceleration across an expanded rage of operations
  • Reduced fuel consumption 
  • Enhanced engine braking
  • Improves engine deceleration for quicker and more efficient shifting
  • Higher torque ratings at low speeds
  • Increase in overall engine performance


There are two common turbochargers that feature the variable geometry, one features a pivoting vane and the other type has moving inner walls. Other turbos show variance in area type, flow type and include sliding ring designs. variable geometry turbochargers are occasionally mistaken for variable nozzle turbines (VNT), and rightfully so. VNT turbochargers are designed to adapt the effective aspect ratio of the turbocharger to adjust for altered conditions. This variable adjustment allows the turbocharger to maintain the optimum aspect ratio at both low and high engine speeds. Manufacturers typically have to specify, in some cases have trademarked, the type of variable geometry turbocharger used in your diesel vehicle. This is because different engine types require specific types of turbochargers in order for the engine to function at peak performance. 


The onboard computer regulates the amount of boost pressure to reduce fuel consumption and increase  overall drivability. The aspect ratio is an important factor in the process of building boost. If the aspect ratio is too large, the turbocharger will produce little to no boost; if the ratio is too high the engine will sputter or choke at high speeds. An improper aspect ratio can create additional problems which can lead to lower performance output; such as increased exhaust manifold pressures or high pumping losses. It is the geometry inside of the turbocharger that the aspect ratio can be maintained at its peak performance. This is what causes a VGT turbocharger to have little lag during acceleration, a low boost threshold and high efficiency at high engine speeds. The attributes discussed above are what  make variable geometry turbochargers an ideal choice for light duty engines like race cars, commercial vehicles and passenger cars.


Why is a turbo wastegate actuator important?


Almost all turbochargers come with a wastegate actuator. A turbocharger wastegate actuator regulates the amount of exhaust gas that flows through the turbo. In trucks, the actuator VGTs also regulate the amount of exhaust that’s recirculated back into the engine inlet which helps overall fuel efficiency and reduces harmful emissions. The wastegate is held down by a spring that holds in the boost pressure until it reaches a specific level determined by the electrical components. VGT turbochargers are  a great option for heavy duty vehicles if you’re looking for a boost in performance, reliability and increased longevity from your engine. The actuator moves the vanes or sliding sleeve within the turbocharger’s holding case to control the amount of exhaust gasses that drive the turbine wheel. The amount of boost available increases or decreases depending on what the electrical component is demanding. A common problem with VGT actuators is that the internal components, vanes or a sliding sleeve, can stick. This basically nullifies any input from the electrical components that are supposed to regulate the amount of boost that should be created. In turn, this causes the vehicle to generate too little or too much boost, resulting in a loss of power.  Heat and pressure will weaken the spring and ultimately damage the turbocharger over time. It is best to recognize the signs of a failing turbo actuator before the turbocharger becomes inoperable. 


The “Superior” Choice: Cummins Turbo Diesel


The majority diesel enthusiasts rank the notorious Cummins turbo diesel engine as the best diesel engine on the market today. Available in a 5.9L or 6.7L, the long or short block engine puts the roads to the test because of its ability to outperform and outproduce every other production engine out there. It was brought to market in 2007 and has only gotten better since then. It is widely used by heavy duty vehicles because of its astonishing 400 horsepower and 1,000 lb/ft benchmarks. The VGT turbocharger produces a 33 psi of manifold pressure


Have your VGT turbo serviced by the experts at AG Automotive!


VGT turbochargers are more complex than the old wastegate turbochargers and require a trained technician to accurately diagnose, service and repair them. Because of their complexity, VGT turbochargers can cost a pretty penny to repair or replace. But there are some things drivers can do to prevent the deterioration and promote the longevity of its components. Other services will help keep the turbocharger clean by improving compression and better fuel & air ratios:

  • Routine engine oil changes and recommended engine flush services
  • Air induction service to check compression ratios and air intake 
  • Injection system flush to ensure the fuel injectors and system are functioning properly
  • Inspection of exhaust aftertreatment system


If your vehicle is experiencing slower acceleration, lower fuel efficiency or are hearing unnatural noises coming from under the hood, Ag Automotive will have you back on the road in no time after we identify that it needs a VGT turbo service. Our expert technicians have the tools and knowledge to test, clean and replace worn turbochargers and or its components quickly and efficiently.


We want the job to be done right the first time, so we ensure your VGT turbocharger is working properly and exceeds the manufacturer’s specifications after our service. We offer our customers a full service inspection of their VGT turbo systems which includes 


  • Removing turbocharger to perform manual clean of variable geometry vanes and unison ring
  • Inspect for coolant residue in intake and exhaust passages (Common problem with EGR cooler failure)
  • Install updated larger turbo drain pipe and new O-rings
  • Inspect and replace turbo outlet boot as needed
  • Remove, inspect, and clean EGR valve and replace gasket and O-ring seals
  • Install EGR baffle kit
  • Clean/Service mass air flow sensor
  • Clean/Service exhaust back pressure sensor and tube
  • Clean/Service air intake temperature sensor
  • Clean/Service manifold absolute pressure sensor and inlet tube and hose
  • Clean/Service EGR valve electrical connector connections
  • Re-torque all turbo boost clamps and check for leaks 
  • Check for FICM and PCM programming updates (Perform as needed)(Billed separately)
  • Clear all codes
  • Clean and test drive
  • Check for proper turbo performance 
  • Recheck for computer codes
  • Final Quality Check


Don’t Second-Guess the Condition of Your Vehicle

Many auto owners struggle to know if the right work was done the right way on their car. As a courtesy, we provide digital vehicle inspections and photos so you can quickly and easily see what our experienced, professional technicians are seeing. Overall, we go the extra mile to help you make informed decisions on the repair and maintenance plan of your vehicle, so you can drive with confidence every time you get behind the wheel.