An ignitable mixture should be formed in the proximity of the spark plug and a very lean one in the remainder of the combustion chamber. Fuel saving is the aim in this operational range (partial load) with an average Lambda of approx. 2.7 to 3.4.
How it works
The air baffles in the picture above - which are the same for all cylinders - are now somewhat closed. The air enters the combustion chamber with a strong swirl. In addition there is a stratified injection in the last third of the compression stroke. If the piston has - as in this case (see picture) - one or two cavities, this indicates wall guidance.If the fuel stream is just added to the whirling air flow, it is air guided. In both cases an ignitable mixture forms in the proximity of the spark plug, and a lean one in the remainder of the combustion chamber.
The design differs substantially amongst the various manufacturers. The design as outlined above with the air buffle and wall guidance of the piston represents only one possibility. The principle of the stratified injection under high pressure is however the same for all manufacturers. Some do not make use of the stratified-charge operation. The promised fuel saving with partial load and stratified-charge operation are not yet comprehensible in reality.
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