ME-SFI TWC heating-up, function - GF07.61-P-3032V

ENGINE 272.920 in MODEL 203 up to Model Year 8

ENGINE 272.922 in MODEL 211

ENGINE 272.940 in MODEL 203 up to Model Year 8

ENGINE 272.941 in MODEL 203 up to Model Year 8

ENGINE 272.942 in MODEL 171 up to Model Year 8

ENGINE 272.943 in MODEL 211, 219

ENGINE 272.944 in MODEL 211

ENGINE 272.945 in MODEL 251 up to Model Year 8

ENGINE 272.946 in MODEL 221 up to Model Year 8

ENGINE 272.960 in MODEL 203 up to Model Year 8

ENGINE 272.963 in MODEL 171 up to Model Year 8

ENGINE 272.964 in MODEL 211, 219

ENGINE 272.965 in MODEL 221 up to Model Year 8

ENGINE 272.966 in MODEL 230 up to Model Year 8

ENGINE 272.967 in MODEL 164, 251 up to Model Year 8

ENGINE 272.970 in MODEL 203 up to Model Year 8

ENGINE 272.972 in MODEL 211

ENGINE 272.975 in MODEL 221 up to Model Year 8

ENGINE 273.922 in MODEL 221 up to Model Year 8

ENGINE 273.923 in MODEL 164 up to Model Year 8

ENGINE 273.924 in MODEL 221 up to Model Year 8

ENGINE 273.960 in MODEL 211, 219

ENGINE 273.961 in MODEL 216, 221 up to Model Year 8

ENGINE 273.962 in MODEL 211

ENGINE 273.963 in MODEL 164, 251 up to Model Year 8

ENGINE 273.965 in MODEL 230 up to Model Year 8

ENGINE 273.967 in MODEL 209

ENGINE 273.968 in MODEL 221 up to Model Year 8

ENGINE 272.940 in MODEL 209

ENGINE 272.960 in MODEL 209

Model 171 shown with engine 272.963

Fig 1: ME-SFI TWC Heating-Up Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The TWC heating-up function heats up the catalytic converters more rapidly to their operating temperature (300 to 450°C) and thus considerably reduces the exhaust emissions in the cold start and heating-up phase.

The ME control unit is able to detect that the operating temperature has been reached and that the catalytic converters are operating at normal efficiency from the signals supplied by the O₂ sensors.

The following conditions determine whether TWC heating is enabled:

Engine starting temperature
Altitude level
Residual heat in the catalytic convertor (from theoretical calculation)
Difference between intake air and engine starting temperatures
Air mass

The following systems are involved in the TWC heating-up:

Ignition system
At idle speed and coolant temperature dependent, the ignition angle is retarded for e.g. 20 seconds and thus the exhaust temperature is increased.
Idle speed control
Dependent on coolant temperature, the idle speed is increased to approx. 1100 to 1300 RPM for a maximum of 20 seconds.
Camshaft adjustment
For TWC heating, special positions are specified separately for the intake and exhaust camshafts
Coolant-temperature dependent transmission shift delay is retarded for automatic transmissions.
Secondary air injection
After starting and during warm-up, the enriched mixture results in more unburned hydrocarbons in the exhaust. The injected air (high oxygen concentration) causes post-oxidation in the catalytic converters. Heat is released as a result, which more rapidly warms up the catalytic converters to operating temperature.

Component description for the ME-SFI [ME] control unit		GF07.61-P-6000V
Component description for an O₂ sensor	O2 sensors upstream of TWC	GF07.04-P-6100V
Component description for an O₂ sensor	O2 sensors downstream of TWC	GF07.04-P-6100VA
Component description for the crankshaft Hall sensor		GF07.04-P-6220V
Component description of throttle valve actuator		GF30.20-P-2020V
Component description for the coolant temperature sensor		GF07.04-P-6040V
Component description for the hot film MAF sensor		GF07.07-P-6000V
Component description for the air pump switchover valve		GF14.30-P-2020V
Component description for the electric air pump		GF14.30-P-2000V
Component description for a pressure sensor		GF07.04-P-6060V
Component description for the ignition coil		GF15.10-P-2100V
Component description for a three-way catalytic converter		GF49.10-P-2010V