ME-SFI Post-Start Enrichment Function

ME-SFI Post-start Enrichment Function




Shown on Engine 119
B11/4 Coolant temperature sensor
K40 Relay module, model 210
L5 Crankshaft position sensor
N3/10 Motor electronics control unit
N15/3 ETC control unit
N16/1 Base module, model 129, 140
X11/4 Data link connector
Y62 Injectors (LH-SFI, HFM-SFI, PEC [LH, HFM, PMS])
CAN Data bus




t1 Starting mixture enrichment (duration e.g. approx. 2 seconds)
t2 Post-start enrichment (duration e.g. approx. 15 seconds at +15 °C coolant temperature)
t3 Warming-up phase (duration dependent on coolant temperature)
A Enrichment rate
a Start
b End of start, start of cutoff of post-start enrichment
c End of post-start enrichment, start of warming-up control

Task
Enriching the fuel-air mixture for a short time after a cold start to ensure that the engine runs smoothly.

Design/function
Post-start enrichment is dependent on:
- Coolant temperature at engine start
- Estimated time after start
- Selector lever position
- Correction programming

Post-start enrichment compensates for the fuel which precipitates on the cylinder walls. The fuel-air mixture is enriched sufficiently until a certain engine speed has stabilized (e.g. 1500 rpm with no gear engaged at +30 °C coolant temperature for about 30 s).