Published: 11-May-2011
2007.0 Range Rover Sport (LS), 303-04F
Fuel Charging and Controls - Turbocharger - TDV8 3.6L Diesel
Turbocharger (G938528)
| Item | Description |
|---|---|
| 1 | Exhaust manifold |
| 2 | Gasket - Exhaust manifold to cylinder head |
| 3 | Oil feed pipe |
| 4 | Stud - Exhaust manifold to turbocharger (3 per turbocharger) |
| 5 | Gasket - Exhaust manifold to turbocharger |
| 6 | Turbocharger support bracket |
| 7 | Shield |
| 8 | Oil drain pipe |
| 9 | Turbocharger assembly |
| 10 | Nut - Exhaust manifold to cylinder head (8 per manifold) |
| Item | Description |
|---|---|
| A | Cool atmospheric air |
| B | Hot compressed air |
| C | Exhaust inlet |
| D | Exhaust outlet |
| 1 | Oil feed connection |
| 2 | Turbine housing |
| 3 | Oil return connection |
| 4 | Actuator lever |
| 5 | Actuator motor |
| 6 | Compressor housing |
Two variable vane Borg Warner turbochargers are fitted to the TDV8 engine, 1 to each exhaust manifold. Each turbocharger works independently from each other supplying air, via twin intercoolers, into the intake manifold. A balance pipe between each bank equalizes the pressure. Each turbocharger has its own electric motor to operate the vanes and is controlled by the Engine Control Module (ECM). The vane positions are varied to control the speed of the turbine wheel maintaining optimum boost pressure over a wide engine speed range and minimising turbo lag (turbo lag is a term used to describe the response time from the time the accelerator is pressed to the time when the turbocharger begins to affect performance), as seen with normal waste-gated turbochargers, during vehicle acceleration.
The exhaust turbine wheel is 39 mm diameter and the compressor wheel is 49 mm diameter. The turbine wheel is made from a high strength high temperature 'Inconel alloy' (a nickel-chromium alloy containing significant amounts of iron, niobium, and molybdenum along with lesser amounts of aluminum and titanium to combine corrosion resistance with high strength) and the compressor is high-grade aluminium alloy. The shaft assembly rotates at a maximum speed of 210,000 rpm to produce a charge air pressure of up to 1.7 bar with a pre-turbine pressure of 3 bar and 800°C (1472°F).
The position of the vanes are controlled by the ECM via a torque motor, lever and linkage rod. A feed back sensor in the motor continuously informs the ECM as to the position of the vanes during the turbochargers operation. If the vanes fail to reach the requested position an error code is generated known as a Diagnostic Trouble Code (DTC).
| Item | Description |
|---|---|
| A | Low engine speed |
| B | Moderate engine speed |
| C | Maximum engine speed |
| 1 | ECM |
| 2 | Actuator motor |
| 3 | Adjusting ring |
| 4 | Vanes |
| 5 | Turbine |
A - Low Engine Speed
At low engine speeds the volume of exhaust gas is low so the vanes are moved towards the closed position to reduce the turbine inlet area. This reduction causes an increase in the gas velocity into the turbine wheel thereby increasing wheel speed and boost.
B - Moderate Engine Speed
As the engine speed increases and the volume of exhaust gas increases and the vanes are moved towards the open position to increase the turbine inlet area and maintain the gas velocity.
C - Maximum Engine Speed
At maximum engine speed the vanes are almost fully open maintaining the gas velocity into the turbine wheel.
Barometric Pressure Sensor
When the vehicle is driven at high altitudes the ambient pressure reduces causing the compressor wheel to do less work for the same boost pressure. To prevent the turbine wheel from over-speeding under these conditions a barometric pressure sensor, located in the ECM, protects the turbocharger by opening the vanes further to reduce the turbine wheel speed. This is known as the altitude margin of the turbocharger.
Turbocharger Lubrication
The rapid acceleration and deceleration response demands of the turbocharger rely greatly on a steady flow of clean oil. The oil supplied from the engine's lubrication system provides lubrication to the turbocharger's spindle and bearings, while also acting as a coolant for the turbocharger centre housing.
To maintain the life expectancy of the turbocharger, it is essential that the oil has a free-flow through the turbocharger and unrestricted return to the engines sump. It is therefore imperative that the engine oil is replenished at regular service intervals with the recommended quality and quantity of oil.
Charge Air Cooler
The charge air cooler is used to increase the density of air as it flows from the turbochargers compressor to the intake manifold.
Compression of the charge air by the turbochargers raises the temperature of the air. This generation of heat expands the air density and consequently less oxygen is able to enter the cylinders, reducing the engines power. To overcome this, the air is routed through the charge air cooler before it enters the engine; the temperature is reduced by transferring the heat to atmosphere.
Cooling of the intake air also helps to reduce engine emissions by limiting nitrogen oxides (NOx) production.