Turbocharger Control Module: Description and Operation

Turbo Boost System Components:

PURPOSE
This system increases the turbo boost pressure during full throttle operation. This results in an additional 15 bhp at 5500 RPM.

The turbo boost is electronically controlled by a turbo boost ECU. The ECU (located in engine compartment in front of passenger side strut tower) uses various input devices to determine the control signal to the control valve. This control valve will regulate the turbo charger wastegate (turbo boost pressure) for optimal performance.

Input devices (the ECU receives):

^ Ignition switch (battery voltage).
^ Engine speed signal.
^ Throttle position signal.
^ Knock signal from fuel injection and ignition ECU.

Output device (The ECU controls):

^ Control valve ground.


NORMAL DRIVING PROGRAM:
During normal driving, the turbo boost is regulated mechanically by the wastegate valve.

The turbo boost system is non operational. It only operates when the throttle position sensor indicates full throttle (full throttle switch closed).


FULL LOAD PROGRAM:
The turbo boost system starts operating when the full load switch in the throttle position sensor is closed.

At full throttle the ECU controls the turbo boost by regulating the pressure acting on the wastegate valve diaphragm. This is done by a signal sent to the control valve which "bleeds off" a grater or lesser amount of air in the charge air pressure hose, therefore reducing the pressure acting on the wastegate valve diaphragm.

The smaller the air pressure acting on the wastegate valve diaphragm, the longer the wastegate valve stays closed. This will allow a higher turbo boost pressure in the intake manifold (increasing power).

The higher the air pressure acting on the wastegate valve diaphragm, the earlier the wastegate valve will open. This would reduce the turbo boost pressure in the intake manifold (decreasing power).

The turbo boost system will disengage immediately if the full load switch in the throttle position sensor opens (throttle not in full load position).

KNOCK CONTROL PROGRAM:
Although the risk of knock at high RPM's is low, it causes high and dangerous combustion temperatures when it occurs.

If the turbo boost ECU receives a knock signal from the ignition ECU, the system will disengage immediately. This will aid in reducing the knocking problem.

The turbo boost system will be inoperative until the throttle has been closed slightly and then reopened to the full load position.