Fuel Stratified Injection (definition inside)
From Audi's website.
In contrast to conventional intake manifold injection on conventional spark-ignition engines, FSI engines inject fuel directly into the combustion chambers, dispensing with the throttle plate. That "unthrottles" the engine, reduces heat loss and thus increases output while reducing fuel consumption. The system uses two charge-air supply modes: stratified charge at partial load and homogeneous operation at full load. In the stratified charge mode, an combustible fuel-air mixture is only produced in a defined zone around the spark plug. The engine management electronics monitor engine load and adjust injection timing, pressure, quantity parameters as well as the air flow inside the cylinder via the air intake channel. At full load, FSI increases compression as well as engine efficiency and performance.
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