2012 911 Section 2-2 11/3/11 10:15 AM Page 32
911 Carrera 911 Carrera S
DME engine electronics
2
2.8 Mixture formation Mixture adaptations The mixture adaptations of cylinder banks 1 and 2 for the ranges RKAT (near-idling range), FRAU (lower load/engine speed range) and FRAO (upper load/engine speed range) are the same as for the previous model.
Injection strategies Starting (inhomogeneous): Triple injection during the compression stroke (for emissions reasons when the engine is cold and to reduce knocking when the engine is warm).
Twice during the intake stroke and once during the compression stroke (with ignition point at 18° crank angle after TDC).
Engine warm (homogeneous, only during the intake stroke): Idle speed: Single injection Acceleration under load, Carrera 3.4-liter: Double injection up to an engine speed of 3,500 rpm Above this engine speed: Single injection Acceleration under load, Carrera S 3.8-liter: Double injection up to an engine speed of 3,500 rpm (under full load: triple injection up to 2,000 rpm) Above this engine speed: Single injection
Variable deceleration fuel cutoff The variable deceleration fuel cutoff is an enhancement of the conventional deceleration fuel cutoff. In principle, this involves controlled interruption of the fuel supply in driving situations where the combustion engine is not required to output any power but is kept moving by the inertia mass of the vehicle (deceleration, e.g. when driving downhill). Compared with the usual deceleration fuel cutoff systems, which resume fuel injection as from a fixed engine speed, variable deceleration fuel cutoff systems resume fuel injection flexibly depending on the driving situation, which may correspond to an even lower engine speed. Depending on the driving situation, fuel injection can resume even later, thereby saving fuel.
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Catalytic converter heating (inhomogeneous):
