Description
"A" exhaust gas outlet
"B" exhaust gas inlet
"C" Compressor inlet
"D" Compressor outlet
(1) turbocharger body
(2) variable geometry control capsule
(3) inlet air compressor
Role
The fixed geometry turbocharger provides air turbo for the engine
Role of the variable geometry turbocharger
- To increase the speed of the exhaust gases that hit the turbine at low engine speeds
- To reduce the speed of the exhaust gases that hit the turbine at high engine speeds
- To adapt the turbine to a variation in the flow of the exhaust gases
Function
"A" exhaust gas outlet
"B" exhaust gas inlet
"C" Compressor inlet
"D" Compressor outlet
(1) turbocharger body
(2) variable geometry control capsule
(3) inlet air compressor
(4) turbocharger shaft
(5) exhaust turbine
The engine is turbocharged by a variable geometry turbocharger controlled by the engine management ECU via a turbocharging pressure regulating solenoid valve
The turbocharger consists of two separate chambers
- A chamber connected to the engine exhaust function (exhaust turbine)
- A chamber connected to the engine inlet function (inlet air compressor)
The exhaust turbine (5) and the inlet air compressor (3) are joined together by a shaft
The turbine, activated by the exhaust gas, drives the inlet air compressor (3) which compresses the inlet air
The engine management ECU controls the turbocharger via the intermediary of the turbocharing pressure regulating solenoid valve
"a" exhaust turbine mobile fins control rod
"b" mobile drive plate
"c" fin lever
"d" mobile fins
The variable geometry control capsule changes the position of the mobile drive plate via the intermediary of the control rod
The change in position of the mobile drive plate causes the fins to pivot
The rotation of the fins on their respective shafts permits
- Variation of the inlet section of the exhaust gases onto the exhaust turbine
- More precise direction of the exhaust gases onto the exhaust turbine
The regulation of the boost pressure is progressive and is managed by the engine management ECU mapping
Operation at low engine speed / turbocharging pressure regulating valve control vacuum capsule not controlled
"d" mobile fins
(5) exhaust turbine
At low engine speed the kinetic energy of the exhaust gases is weak
- The variable geometry turbocharger increases the kinetic energy of the exhaust gases by decreasing the section through which the exhaust gases must pass
- In addition the movable vanes in the closed position accurately direct the exhaust gases onto the exhaust turbine (5)
The speed of rotation of the exhaust turbine (5) is accelerated at low engine speed
Operation at high engine speed / turbocharging pressure regulating valve control vacuum capsule controlled
"d" mobile fins
(5) exhaust turbine
At high engine speed the kinetic energy of the exhaust gases is strong
- The variable geometry turbocharger decreases the kinetic energy of the exhaust gases by increasing the section through which the exhaust gases can pass
- In addition the movable vanes in the open position direct the exhaust gases on to the exhaust turbine (5) less accurately
The speed of rotation of the exhaust turbine (5) is reduced at low engine speed
Electrical features
Not applicable
Programming/initialisation
Not applicable