Exam Question

A Variable Turbine Inlet (VTI) turbocharger, commonly known as a Variable Geometry Turbocharger (VGT) or Variable Nozzle Turbocharger (VNT), optimizes engine performance by adjusting the geometry of the turbine inlet to regulate exhaust gas flow.
The turbine housing contains movable vanes that surround the turbine wheel. These vanes can change their angle to vary the cross-sectional area of the turbine inlet, controlling the speed and pressure of exhaust gases impacting the turbine.
At low engine speeds, the vanes close to create a narrower passage. This accelerates exhaust gases onto the turbine wheel, increasing its speed and generating higher boost pressure quickly, which reduces turbo lag and improves low-end torque.
At higher engine speeds, the vanes open to create a wider passage. This allows a greater volume of exhaust gases to pass through, preventing excessive boost and maintaining optimal performance.