The REA is directly controlled by the Engine Control Module (ECM). The ECM constantly controls the position of the actuator
using input information from various engine and vehicle mounted sensors. A feed back sensor within the REA continuously
informs the ECM of the actuator position during turbocharger operation. In the event that the variable vanes fail to reach
the requested position, a Diagnostic Trouble Code (DTC) is stored in the ECM memory.
PRINCIPLES OF OPERATION
The turbocharger uses the energy of the exhaust gas flow from the engine to provide compressed (charged) air to the
intake air system. The variable geometry vanes make sure the turbocharger produces the required level of intake air boost
pressure for the current engine operating conditions.
The turbocharged engine provides the following advantages over a conventional naturally aspirated engine:
Greater volumetric efficiency
Improved engine power and torque
Reduced fuel consumption
Reduced emissions
Re-use of exhaust gas energy
Un-affected by altitude
Limited periods of over-boost for immediate engine demands.
Typical Rotary Electronic Actuated Turbocharger
Item
Part Number
Description
A
-
Low engine speed
B
-
Moderate engine speed
C
-
Maximum engine speed
1
-
ECM
2
-
Rotary Electronic Actuator
3
-
Rotary adjusting ring
4
-
Variable vanes
5
-
Turbine wheel
In response to signals from various sensors, the ECM controls the REA to operate the rotary adjusting ring. Movement of
the adjusting ring alters the pitch angle of the variable vanes to deflect the flow of exhaust gas onto the inside center or
outside edge of the turbine wheel.
The maximum position of the turbocharger variable vanes (fully open) is also the emergency default position in the event
of an electrical fault. The REA will move the variable vanes to the fully open position to prevent engine damage due to
excessive boost pressure.
A - Low Engine Speed