ME-SFI warm-up control, function - GF07.61-P-3022AMG

ENGINE 156.980 in MODEL 164, 251 up to Model Year 8 

ENGINE 156.982 in MODEL 209 

ENGINE 156.983 in MODEL 211, 219 

ENGINE 156.984 in MODEL 216, 221 up to Model Year 8 

Fig 1: Identifying ME-SFI Warm-Up Control Function Diagram

Courtesy of MERCEDES-BENZ USA

The fuel-air mixture is further enriched via the warm-up control after start and post-start enrichment. The condensed fuel on the still cold cylinder barrels and intake ports is compensated for through enrichment of the warm-up control.

The additional quantity of fuel is metered to the engine by the ME-SFI [ME] control unit based on the performance map. Injection times are extended accordingly for this purpose.

Warm-up control is dependent on:

• Coolant temperature
• Intake air temperature
• Engine speed
• Engine load
• Camshaft position
• Correction programming with STAR DIAGNOSIS

At close to idle operation, the enrichment rate is mainly dependent on the coolant temperature. At partial load the air mass is also used.

Once lambda regulation is releases it then monitors the enrichment rate.

The camshaft position determines the exhaust gas recirculation rate via the valve overlap. As the hot exhaust gases warm up the combustion chamber, the fuel vaporization changes and the enrichment rate must be tuned to match it.

Using the two-disk thermostat the coolant is led in such a way that it warms up as soon as possible (thermal management).

During warm-up, ignition angles are determined from a particular performance characteristic.

Fig 2: Identifying Enrichment Rate Graph

Courtesy of MERCEDES-BENZ USA