GF14.20-P-3000OHL | Exhaust gas recirculation, function | 5.5.08 |
ENGINE 642.9 in MODEL 221.0 as of Model Year 09 /Modification Year 08
ENGINE 642.9 in MODEL 221.1 as of Model Year 09 /Modification Year 08
General function requirements
Circuit 61 ON
- Exhaust gas recirculation (EGR) - general
The EGR lowers the portion of nitrogen oxides (NOX) in the exhaust. This takes place via the following 3 processes:
- Reduces the (O2) concentration in the combustion chamber
- Reduces the amount of exhaust flow
- Lowers the combustion temperature by raising the heat absorption capacity of components (for example, water (H2O) and carbon dioxide (CO2)) which are not involved in the combustion process, but which have an effect on it
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Function sequence
EGR is active in the wide load and rpm ranges below full load. The EGR rate is determined according to engine load, engine speed, coolant temperature and atmospheric pressure.
To do this, the CDI control unit (N3/9) reads in information from the following components:
- Left hot film mass air flow sensor (B2/6)
- Right hot film mass air flow sensor (B2/7)
- Charge pressure sensor (B5/1)
- Charge air temperature sensor (B17/8)
- Accelerator pedal sensor (B37)
- Crankshaft Hall sensor (B70)
- Internal atmospheric pressure sensor
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After evaluating the input signals, the CDI control unit uses a stored performance map to actuate the left exhaust gas recirculation positioner (Y27/9) with a Pulse Width Modulation (PWM) signal. The orifice area is upsized, downsized, or closed completely by the left exhaust gas recirculation positioner, depending on actuation by the CDI control unit. More, less or no exhaust at all is fed back into the charge air manifold depending on the valve position.