The idea for VNT™ came from the need for rapid boost response. Large, high-flow turbines, while powerful and efficient at a steady state, are not as responsive and do not provide as much low speed boost as small, low-flow turbines. To overcome this problem, the Garrett® VNT™ turbocharger adjusts the gas flow cross section at the inlet of the turbine wheel in order to optimize turbine power with the required load. At low engine speed and low gas flow, the vanes of the VNT™ close, thereby reducing the inlet area to the turbine. This results in an increase in turbine inlet pressure, which increases turbine power and drives higher engine boost pressure. At high engine speeds and load, the vanes open, thereby increasing the turbine inlet area. This has a combined effect of preventing over-boost and reducing engine outlet pressure for improved fuel economy at high load operating condition.
Currently, Garrett® VNT™ technology has two design variations: Multivane™ VNT™ and Slidevane™ VNT™. While the ultra-efficient Multivane™ VNT™ uses a system of synchronized pivoting vanes to control boost, resulting in maximum torque and fuel economy at all speeds, the Slidevane™VNT™ model employs fixed vanes and a sliding nozzle piston system, providing a cost-effective and reliable solution for smaller applications.
