VGT/VNT Turbochargers are mostly used for diesel engines.
MuchBoost uses lots of VNT systems for the turbos.
The variable geometry turbine allows significant flexibility over the pressure ratio across the turbine. This adaptability can be employed in diesel engines to enhance low-speed torque characteristics, lessen turbocharger lag, and drive EGR flow. The swinging vane design and the moving wall design are two of the most popular variations of variable geometry turbochargers.
The benefits of variable geometry turbines, compared to fixed geometry turbines:
no throttle loss of the wastegate valve,
higher air-fuel ratio and high peak torque at lower engine speeds,
better vehicle acceleration,
allows for engine braking,
allows for raising exhaust temperature for servicing,
allows driving EGR flow in diesel engines with HPL (High-Pressure Loop) EGR systems.
There are lots of brand names for VGT systems:
VGT– Variable Geometry Turbocharger (Cummins/Holset),
VNT – Variable Nozzle Turbine (Honeywell/Garrett),
VTG – Variable Turbine Geometry (BorgWarner, ABB),
VG – Variable Geometry (MHI),
VGS – Variable Geometry System (IHI),
VTA (variable Turbine Area (MAN)
Compared to a fixed geometry turbine, the variable geometry turbine allows significant flexibility over the pressure ratio/flow relationship across the turbine. The peak efficiency of a variable geometry turbine occurs at about 60% nozzle opening. It is usually comparable to or a few percent lower than that of a fixed geometry turbine. However, efficiency drops off rather quickly as nozzle opening is reduced or increased from a mid-vane opening position.
All of our turbos with the VNT systems are precisely and perfectly calibrated. We use modern VISCOM and CIMAT flow benches.
Below are some examples of our turbos with VNT:
Although VNT is mostly present in turbos meant for diesel engines, there are times when they’re used in petrol engines turbos.