VW Breaks New Ground With Cylinder-Deactivation System

Volkswagen may be a little late to the party with its cylinder-deactivation technology, but the German auto maker says its system is breaking ground all the same as the first to be implemented with a high-volume turbocharged 4-cyl. engine.

Employed on VW’s new 1.4L TSI engine, the system shuts down two of the four cylinders under mid-load situations, improving fuel economy by about 3 mpg (1.3 km/L) in the European driving cycle, the auto maker says.

Twin-lobe cam sleeve.

The stop/start system that shuts down the engine when the vehicle is in neutral improves fuel economy another 1.4 mpg (0.6 km/L).

Luxury-brand Audi is using the same technology on its new 4.0L twin-turbo V-8 engine that will power the upcoming S6, S7 and S8 models that will debut at the Frankfurt auto show this month and hit the market in the spring.

VW’s new 1.4L pumps out 138 hp and 185 lb.-ft. (251 Nm) at 1,500-4,000 rpm and will meet Euro 6 emissions standards. It will bow in Polo and Golf models in early 2012, the auto maker says.

The cylinder-deactivation system uses two sets of actuators to shift the intake and exhaust cam sleeves a few millimeters, sliding a zero-lift profile lobe over the roller-cam followers to shut down the valves on two of the four cylinders.

When all four cylinders are needed, a full-profile cam slips back into position to re-activate the valves.

VW says the all-mechanical switchover process takes a half revolution of the camshaft and lasts between 13 and 36 milliseconds, depending on engine speed.

A throttle pedal sensor is used to detect the motorist’s driving style. If a non-uniform pattern is occurring – such as during sporty driving – the deactivation system shuts down.

A readout on the dash for instant fuel economy is the only indication of whether the system is engaged.

The actuators, camshafts and bearing carriers are integrated into the cam cover, and the entire system weighs about 7 lbs. (3.2 kg), VW says.