Direct Petrol Injection System with Bosch Motronic MED 7 - Volkspage

Fundamentals
Operating modes
In addition to "stratified charge mode" and "homogeneous charge mode", the 1.6l - 81kW FSI engine has
a third operating mode: homogeneous lean charge mode. This operating mode offers a further
reduction in fuel consumption compared to lambda=1 mode with exhaust gas recirculation.
The engine control unit selects the operating mode depending on torque, power, exhaust gas and safety
requirements.
Stratified charge mode
The engine runs in stratified charge mode up to
the medium engine load and speed range.
Through mixture stratification in the combustion
chamber, the engine can be operated at a total
lambda of approx. 1.6 to 3.
- A highly ignitable mixture forms around the
spark plugs at the centre of the combustion
chamber.
- This mixture is enveloped by an outer layer
which ideally comprises fresh air and
recirculated exhaust gas.
Homogeneous lean charge mode
In the transition zone between stratified charge
mode and homogeneous charge mode, the
engine runs in homogeneous lean charge mode.
The lean mixture is distributed homogeneously
(evenly) throughout the combustion chamber. The
air/fuel ratio is approximately lambda 1.55.
Homogeneous charge mode
At higher engines loads and speeds,
the engine runs in homogeneous charge mode.
The air-fuel ratio in this operating mode is
lambda=1.
Engine load
Homogeneous charge mode
Homogeneous lean charge mode
Stratified charge mode
8
253_085
Engine speed