Electronic Throttle Actuator: Description and Operation

GF30.20-P-3015MAW Electronic Accelerator Function
ENGINES 156.9 in MODEL 204.0 /2 /3, 212.0 /2

Function requirements for the electronic accelerator, general points
^ Circuit 87M (engine timing ON)
^ Engine running

Electronic accelerator, general points
The electronic accelerator function (EFP) (N3/10) integrated in the ME-SFI control unit and controls the opening angles of the throttle valves according to driver requirements and operating conditions.

The ME-SFI control unit controls the throttle valve positions according to the following sensors and signals:

- Accelerator pedal sensor (B37), accelerator pedal position
- Electronic stability program control unit (N30/4) or Premium electronic stability program control unit (N30/7) (on model 212 with DISTRONIC PLUS), brake actuation via chassis CAN (CAN E)
- Electronic Stability Program control unit cruise control request, over the chassis CAN
- Radar sensors control unit (N62/1), DISTRONIC request chassis CAN (for model 212 with DISTRONIC PLUS)
- Fully integrated transmission controller unit (Y3/8), gear range via the drive train CAN (CAN C)
- Fully integrated transmission controller unit, reverse travel signal via the drive train CAN

The requirements of the torque coordination function are also taken into account.

Function sequence for electronic accelerator
The function sequence is described in the following Operation steps:
^ Function sequence for throttle valve actuation
^ Function sequence for throttle valve damping
^ Function sequence for reverse travel
^ Function sequence for adaptive accelerator pedal

Function sequence for throttle valve actuation
Depending on the characteristics map, the ME-SFI control unit actuates the front and rear throttle valve actuators (M16/3, M16/4) according to the accelerator pedal sensor. For this purpose the ME-SFI control unit actuates the actuator motors (M16/3m1, M16/4m1) in the throttle valve actuators with a pulse width modulated signal (PWM signal).

The opening angles of the throttle valves are only determined by the accelerator pedal parameters if there are no limiting functions active (for example, cruise control request).

Actual value potentiometers 1 and 2 (M16/3r1, M16/4r1, M16/3r2, M16/4r2) send the current throttle valve positions to the ME-SFI control unit.

Function sequence for throttle valve damping
The ME-SFI [ME] control unit controls the throttle valve damping according to the following sensors and signals:

- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor, accelerator pedal actuation (fast, slow)
- Crankshaft Hall sensor (B70), engine speed
- Front and rear throttle valve actuator, throttle valve positions
- Electronic Stability Program control unit, vehicle speed via the chassis CAN

The purpose of throttle valve damping is to delay the closing of the throttle valves down to the idle speed range if the accelerator is released suddenly. In this way, the engine torque reduces slowly and the vehicle does not slow down with jerks.

Function sequence for reverse travel
If the fully integrated transmission controller unit transmits the reverse travel CAN-signal, the ME-SFI control unit opens the throttle valves slowly and the maximum opening angle is limited to about 50%. This optimizes ride comfort and driving safety when reversing.

Function sequence for adaptive accelerator pedal
The ME-SFI [ME] control unit recognizes how the accelerator pedal is being actuated and switches between two characteristic curves. After a 50% pedal travel, about 80% of the engine load is released for a sporty driver and 40% of the engine load is released for a relaxed driver. There is no further difference felt above a pedal travel of about 90%.

If the calm driver characteristic is active (for example, after a long journey on the freeway), the accelerator pedal at first has to be pressed unusually far in order to obtain high acceleration.

Further functions which support the electronic accelerator and which are described in other documents are:
- Engine speed control
- Cruise control
- DISTRONIC PLUS (on model 212 with DISTRONIC PLUS)
- Torque coordination
- Engine limp-home mode