Audi has released a video animation demonstrating how its "cylinder on demand" (COD) valve lift system works.

Audi has released a video animation demonstrating how its "cylinder on demand" (COD) valve lift system works.

The first Audis to incorporate the technology were the 4.0 TFSI equipped 2012 Audi S6, S6 Avant, S7 Sportback and S8. Now Audi has included COD in the 1.4-liter TFSI four-cylinder engine found in the Audi A1 which produces 138 hp (103 kW), 184 lb-ft (250 Nm) torque, 4.1L/100km (60.1 mpg UK) and CO2 emissions of 109g/km. This is a savings of 0.4L/100km (5 mpg UK). Furthermore, the 1.4-liter TFSI engine without COD achieves 5.3L/100km (53.3 mpg UK) and 122g/km.

Operationally, COD engages at low to moderate engine speeds. The COD system is ready to engage all the time as Audi has developed a control logic that monitors driving conditions and behavior. When the driving conditions are correct, the system confirms that COD is activated by showing an indicator light in the instrument cluster. COD will automatically disengage if driving conditions change or either accelerator or brake pedal are pressed. The process is seamless and takes only one turn of the camshaft.

Technically, the system closes the inlet and exhaust valves of middle cylinders 2 and 3 by means of sliding sleeves on the camshafts. Just before this happens, the combustion chambers are filled with fresh air and fuel injection and ignition are shut down. As a result, the reduced internal cylinder pressure compared to the injection of exhaust gas is a key factor in achieving increased efficiency.

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Audi A1 Sportback cylinder-on-demand animation [video]