ME-SFI Limiting Maximum Engine Speed Function

ME-SFI Limiting Maximum Engine Speed Function




Shown on engine 119 in model 210
K40 Relay module up to 2/97
L5 Crankshaft position sensor
N3/10 ME-SFI control unit
N47-1 ASR/SPS control unit
Y62 Injectors (LH-SFI, HFM-SFI, PEC [LH, HFM, PMS])
CAN Data bus

Task
Limiting maximum engine speed

Function
The ME-SFI control unit detects the engine speed from the signal supplied by the crankshaft position sensor. Engine speed is limited by shutting off the fuel injectors in the following conditions as a protection for the engine and the drive train:

1. Torque converter protection in selector lever position P/N
Engine speed is limited (e.g. to approx. 3800 rpm for engine 120) in order to protect the torque converter from excessive static inner pressure in selector lever position P and N (no power flow).

2. Limiting maximum engine speed when driving
In order to protect the engine from the consequences of impermissibly high revs, engine speed is limited to 6200 rpm and, after a further 10 seconds, to approx. 6000 rpm (e.g. engine 120). The vehicle speed information for detecting the drive mode is received by the ME control unit via CAN from the control unit for traction system (ABS, ASR, ETS or SPS, according to model and equipment).

3. Safety fuel shutoff
If the throttle valve actuator is faulty, the fuel injection valves are shut off at engine speeds of approx. >1400 rpm, and operated again at approx. <1200 rpm (engine surges greatly).