Some actual petrol engines uses the stratified-charge mode.
In this stratified-charge mode the petrol will be injected to
At stratified-charge mode the petrol is injected to the combustion chamber in a way, that only at the area around the spark plug is an explosive mixture (lambda = 0.5 to 1.0). In the rest oft he combustion chamber there is a non ignitable lean mixture (lambda 1.5-2.5).
Because of the exces air ratio in the combustion chamber the nitrogen oxides in the exhaust gas cannot be reduced in a normal 3-way-catalyst. Here a nox catalyst and a nox sensor will be neccessary to store the nitrogen oxides.
An operation on statified-charge mode isn’t possible all the time (e.g. if you drive at full load you have to inject more fuel, here the area with the explosive mixture around the spark plug will be increased).
Normal engine operation mode at lambda = 1.
Limp home / Emergency program:
The engine ECU will start the emergency program at implausible measured exhaust parameters. Here the operation mode will be homogenous.
The fuel injection pressure will be at 5bar or 100bar
The computed sulfur mass oft he NOX catalyst in mg.
Actual rpm of your engine.