Audi proves its exceptional know-how in the field of engine construction with COD (cylinder on demand) cylinder deactivation technology, which reduces fuel consumption by up to 20 percent . The innovative cylinder deactivation system already works in three petrol engines: 1.4 TFSI COD , 4.0 TFSI COD and now also W12 COD in the new Audi A8 L (photo in the gallery).
Audi COD technology is a universal solution that applies equally well to a four-cylinder engine with direct fuel injection as a V8 TFSI unit or a naturally aspirated twelve-cylinder. The COD system deactivates half of the cylinders in all engines at low to medium loads and revs until the driver gives the command to accelerate hard again. The efficiency in the active cylinders will increase as they start to work in the area of higher load.
Activation and deactivation takes place so smoothly and smoothly that the driver does not notice these changes , or only when looking at the on-board computer. Active engine beds in eight-cylinder models eliminate unwanted vibrations . The ANC (Audi Noise Cancellation) system uses precise sound waves with opposite phase to eliminate disturbing frequencies when driving with deactivated cylinders. Depending on the model, the mentioned solutions are used separately or in combination.
In the 1.4 TFSI COD engine, cylinders two and three are switched off; in the 4.0 TFSI engine cylinders two, three, five and eight. The cylinders are deactivated by turning off the ignition and fuel injection . Sliding the sleeves on the camshafts with two different cam profiles via electromagnetically actuated pins closes the valves . Before this, the combustion chambers are filled with fresh air to reduce the internal pressure in the cylinders .
The 368 kW (500 hp) W12 engine uses a special variant of COD technology, where the valves remain open . The system first shuts off fuel injection and ignition for all cylinders on the left bank, leaving the engine running on six cylinders . Before the temperature of the catalyst drops too low, the operation of the left bank of cylinders will resume and the right bank of cylinders will be deactivated. During extended half-cylinder operation , both rows of cylinders are alternately activated and deactivated .
COD technology fundamentally reduces fuel consumption. For example, the RS 6 Avant and RS 7 Sportback models have fuel savings of around five percent in the EU combined cycle. The 4.0 TFSI COD engine , which provides a supreme output of 412 kW (560 hp) in these models, consumes an average of just 9.8 liters of gasoline per 100 kilometers. For Audi A3 models, where the 1.4 TFSI COD engine is tuned to a maximum output of 103 kW (140 hp), the drive unit uses an average of only 4.7 liters of fuel per 100 kilometers. In the combined EU cycle, cylinder deactivation saves approx. 0.4 liters per 100 kilometers. With an optimal driving style, it can be up to 20 percent .
Source: Audi
