Today almost every modern diesel and also petrol engines are equipped with an exhaust gas turbocharger to increase engine performance and efficiency. To ensure that the optimum boost pressure is always present, it has to be adjusted to suit the particular load condition. In modern vehicles, this is done by the electronic boost pressure control.
1. Electromechanical control device for the exhaust gas turbocharger – Turbocharger Actuator
The turbocharger actuator, also called control box or boost pressure regulator, is an electronic control device for adjustable turbochargers and is predominantly used for Variable Nozzle Turbine (VNT) and Variable Turbine Geometry (VTG) turbochargers.
In these turbochargers with variable turbine geometry, the actuator reliably and precisely controls the movement of the guide vanes. Through the adjustment of the guide vanes, the exhaust gas flow onto the turbine wheel is influenced, thus changing the boost pressure which can then be optimally adjusted to match all speed ranges. The required boost pressure is regulated according to a map stored in the engine control unit. The engine control unit sends the required boost pressure in the form of a signal to the turbocharger actuator via a data bus connection. The actuator adjusts the guide vanes accordingly in line with the required angle setting contained in the signal.
Advantages of an electronic control device are:
- Faster response of the turbocharger already at low engine speeds
- Exact adjustment of the guide vanes in all speed ranges
- Improvement of the emission values
2.THE TURBOCHARGER ACTUATOR: DESIGN AND FUNCTION
The main function of the actuator is to bring the shaft into the position specified by the control unit or into that position calculated as a result of the map diagrams.
With the help of the contactless, inductive position sensor (CIPOS sensor), the position of the shaft is continuously determined and actively reported back. Angles are measured inductively using a non-contact and consequently wear-free method, thus guaranteeing high measuring precision throughout the entire lifetime. The insensitivity to magnetic fields and the high level of temperature stability, in particular, are the characteristic qualities of the CIPOS technology implemented here.
In addition to the CIPOS sensor responsible for precise positioning, the integrated electronics also include control of the electric motor and error diagnosis. In this way, errors can be detected, reported back and appropriate reactions automatically derived from them. The actuator has a flexible operating angle area and carries out controlled movement up to the limit stop.
Depending on the model, communication in the vehicle is possible both via CAN bus and also via a pulse-width modulated signal (PWM).
LStructure/design of the HELLA turbocharger actuator:
(1) Upper housing cover
(2) Printed circuit board
(3) Worm gear
(5) Retaining bracket for motor
(6) Electric motor
(7) Gearbox housing
(8) Fastening element /lever
(11) Drive segment
3.ELECTRONIC BOOST PRESSURE CONTROL/REGULATOR DEFECT
A failure of the electromechanical turbocharger actuator can occur in the following way:
- Performance loss
- Poor or insufficient acceleration
- Engine warning light comes on
- Reduction of vehicle speed
- Vehicle runs in “emergency mode”
4. CAUSE OF A DEFECTIVE ELECTRONIC BOOST PRESSURE
CONTROL/REGULATOR: CAUSE OF FAILURE
Causes of a defect on the turbocharger actuator can be:
- Rod of control device or guide vanes stiff or defective
- Corrosion of the electrical components as a result of environmental influences (water, salt, etc.)
- Mechanical damage as a result of external impact
A defect in the gearbox of the turbocharger actuator is usually preceded by a defect in the guide vane adjustment on
the turbocharger. Over time, the exhaust gas flow creates heavy contamination inside the turbocharger. Such soot
formation impairs the functioning of the guide vanes. This leads to a higher torque requirement for the entire actuator
and ultimately to gearbox damage at the actuator and error entry in the engine control unit.
Purchase and consult the Turbo Electronic Actuator link: