Overheating/Pinging Protection Function

Overheating/pinging Protection Function




Shown on Engine 119
B2/5 Hot film MAFsensor
B11/4 Coolant temperature sensor
B17 Intake air temperature sensor
L5 Crankshaft position sensor
M16/1 Electronic accelerator (EA)/ cruise control (CC)/ idle speed control (ISC) actuator
N3/10 ME-SFI control unit
T1/1-T1/8 Ignition coils, cylinder 1 to 8

Task
Preventing engine damage resulting from excessively high coolant temperature.

Design/function
If the engine temperature is too high, the ignition timing point is retarded by the ignition system as an overheating and pinging protection. Activation of the pinging protection correction begins at a coolant temperature of approx. 100 °C and is active only when engine is under load.

The ignition timing is retarded e.g.:
e.g.: 100° C and full load 0° crank angle later
105° C and full load 1.4° crank angle later
120° C and full load 3.2° crank angle later

The following information is processed in the ME-SFI control unit for this purpose:
- Engine speed/crankshaft position
- Air mass (boost pressure in supercharged engines)
- Coolant temperature.

Note: The correction of the pinging protection and of the intake air are added together, a coolant temperature of e.g. 120 °C and an intake air temperature of 50 °C result in a maximum retardation of 11° crank angle at full load.