100 ENGINE2.2LDICOR Variable Turbin Technology (VTT) uses a variable nozzle turbine (VNT) - Turbocharger VariableNozzle Turbine Turbocharger (Fig. 212) Traditional turbochargers generate their maximum boost pressure at high engine speed/load conditions. At partial loads and at low engine speeds these turbochargers generate limited boost. This in turn limits the torque generated by the engine. Over-boost is prevented with an exhaust bypass or "waste gate" that limits the exhaust gas energy reaching the turbine and this boost control is extremely limited. This turbocharger enables exceptional flexibility in matching and controlling engine air requirements over extremely broad speed & load range by accommodating variable exhaust flow rates. This results in higher power and torque under all operat ing condi t ions, resul t ing in excel lent acceleration & driveability under various speed & load conditions Higher Power From low to high engine speeds, the turbocharger with VTT delivers high a boost pressure with low pumping losses resulting in higher power throughout engine speeds. Higher Torque and ImprovedTransient Response At low engine speeds, the VTT turbocharger accelerates more quickly due to lower inertia & variable multi turbine vanes. This helps in increasing the available high torque immediately after pressing the accelerator pedal resulting in very good transient response. Lower Fuel ConsumptionandEmissions A lower engine outlet pressure directly reduces fuel consumption by reducing engine pumping losses. Optimized boost pressure control by the engine management system further improves fuel economy and reduces emissions throughout the operating range of the engine. Construction and Function The VNT Turbocharger has a set of movable vanes in the turbine housing, and they control boost. At low engine speeds when exhaust flow is low, the vanes are partially closed. This increases the pressure of the exhaust pushing against the turbine blades, making the turbine spin faster and generating more boost. As engine speed increases, so does exhaust flow, so the vanes are opened to reduce turbine pressure and hold VariableNozzle TurbineTurbocharger (VNT) Fig. 212 VNT cross sectional view
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