Intrusive Turbo Position And Response Monitoring

The 6.7L engine is equipped with an oil pressure actuated, variable vane turbocharger. The variable geometry turbo (VGT) does not have a position sensor, so the position is inferred using a duty cycle to position transfer function. To verify actual position based on the nominal transfer function, an intrusive monitor sweep is performed. When entry conditions are met, the intrusive monitor for VGT closes the EGR valve, opens the throttle and then commands the output PWM to open and closed position for a calibratable duration. Typical values are 85%, then 25%. The minimum and maximum MAP values are saved and compared to a threshold. If the desired separation in MAP pressure isn't achieved, a fault is detected. If the desired separation in MAP is achieved, the test is considered a pass.

Courtesy of FORD MOTOR CO.

In the example above, at 1871 seconds, the EGR valve is commanded closed, after 3 seconds with EGR off and turbocharger at 85% position, the turbocharger is opened up to. 25% position. The 25% position is held for 4 seconds. If desired separation of 2 kpa at sea level is achieved the test is considered a pass. If desired separation isn't achieved the test is completed and failed.