Most of us know the meaning of the turbocharger but don’t know about the variable geometry turbocharger. It is also known as the Variable Nozzle Turbine (VNT) and abbreviated as the VGT. VGT is often called as the VG Turbocharger.

This type of the turbocharger was used first in the car, Honda Legend in 1999 in Japan. It was first developed by the Garrett (Honeywell). Nowadays, many companies like Borg Warner, Mitsubishi, and heavy Industries have been developing such VG turbochargers.
Also Read: Supercharger vs. Turbocharger

Before understanding the working of the variable geometry turbocharger, let’s take a brief glance at the turbocharger. A turbocharger consists of the turbine and compressor. A turbine and compressor are connected by the axle. Basically, as the fuel burns, the hot gases go into the atmosphere via the turbine section of the turbocharger. As the hot gases pass through the turbocharger, its turbines start rotating. As the turbine is connected to the compressor, the fan of the compressor also starts rotating but in opposite direction as that of the turbines. The compressor does the work of the suction and it takes the surrounding air into the engine.
variable geometry turbocharger, Vgt

That means that turbine does the work of throwing exhaust gases into the atmosphere while the compressor does the work of taking the surrounding air into the engine for better burning of the fuel. But here the problem is that when the exhaust gases have a very high speed then only the turbine rotates very fast and then the compressor rotates. The high speed of the exhaust gases means the high speed of the vehicle. So, that means the turbocharger is workable only if you are driving your vehicle with a high speed. This is the reason behind the invention of the turbocharger.
Also Read: Supercharger vs. Turbocharger

If you are driving your vehicle with a very low speed then, the speed of the exhaust gases will be very less. As these exhaust gases pass through the turbine section, the turbine will not rotate and thus the compressor will not rotate. So, the peak-up, as well as mileage of your vehicle, will decrease. All of this will lead to the malfunctioning of your vehicle.

variable geometry turbocharger

In the case of variable geometry turbocharger, vanes are present around the compressor as well as the turbine. When the speed of your vehicle is very fast then, exhaust gases will have high speed. This exhaust gases then pass through the vanes of the turbocharger. The vanes are designed in such a way that in case of the high speed of the exhaust gases they will decrease the pressure of the gas and thus the gas then rotates the turbine at a moderately high speed rather than very high speed. So, the corresponding compressor fans also start rotating with the speed as that of the turbine and take the surrounding air into the engine which in turn helps in burning the fuel fast.

Now, when the speed of your vehicle is very less that means the exhaust gases will travel to the vanes with a very low speed. Now, the vanes increase the pressure of the exhaust gases and increase their speed. Now, this exhausts gases with a high-speed pass through the turbine and increase the speed of the turbine. As the turbine rotates, the compressor also starts its work of taking air into the engine. And thus, maintains the efficient burning of the fuel.

Following are the advantages of the variable geometry turbocharger:

  • Due to this type of the turbocharger, the vehicle remains in the good working condition.
  • The second benefit of this is that it helps in maintaining the mileage as well as the peak-up of your vehicle.
  • As it gives a proper amount of air to the engine of the vehicle, the fuel burns efficiently and thus, the vehicle will accelerate easily.
  • It works even at lower speed of the vehicle as compared with a normal turbocharger.

Uses of the VG Turbocharger:

  • The VG Turbocharger is mostly used in the trucks.
  • They also find their application in the two-wheelers, cars as well as in different power plant projects.