Volkswagen cuts its four cylinder losses
Cylinder deactivation cuts 8g/km from new 1.4 TSI gasoline direct injection turbo engine
- Published in News.
Lifting engine efficiency: variable valve train deactivates two of the four cylinders
Cylinder deactivation isn't just for vee engines. Volkswagen is applying the technology to four cylinder gasoline units too, improving part-load fuel efficiency and reducing CO2 emissions by 8g/km on the NEDC test cycle.
The first application is the 1.4-litre TSI direct injection turbo engine, which will be launched in early 2012. The existing 1.4 is widely used by VW, Audi, Seat and Skoda in B-, C- and D-segment models.
VW said: “The system temporarily deactivates two of the four cylinders under low- to mid-load. In the EU drive cycle this saves 0.4-litres of gasoline per 100km. Savings may increase to over one litre under certain driving conditions.”
Using only half of the cylinders whenever possible reduces pumping and thermal losses, while the other two cylinders operate at a higher, more efficient load point. Deactivation is achieved by cutting fuel supply and closing intake and exhaust valves on cylinders number two and three. This is performed by electromechanical actuators engaging zero-lift cams via pins and milled guide slots.
The process takes no more than 36ms. Boundary conditions are that engine speed is between 1,400 and 4,000rpm and torque output is between 25 and 75Nm. In the case of the 1.4 TSI, this applies to almost 70% of the distance covered in the NEDC cycle. The engine's full-load ratings are 103kW and 250Nm from 1,500-4,000rpm.
VW said that the switch should be almost imperceptible to drivers and that they will only be informed of the switch by a message in the instrument cluster if set to display instantaneous fuel consumption.
Cylinder deactivation will also be applied to the 4-litre twin-turbo V8 that will be used in the Audi S8, S7 and S6.. By cutting cylinders 2,3,5 and 8 the technology can reduce emissions by up to 19g/km on the test cycle. In these applications a message is always displayed but the transition is seamless, thanks to active engine mounts and a noise-cancellation system.
Bentley will also use a version of this engine to cut emissions of its Continental GT to 246g/km CO2, but the firm will use other measures to manage the change in NVH characteristics.
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