Bentley develops W12 cylinder deactivation

  • 13-Mar-2015 02:06 EDT
Bentley Flying Spur W12.jpg

For Bentley's new W12 cylinder deactivation, the engine control unit deactivates one bank of six cylinders while leaving the valves to operate as normal.

Luxury car manufacturers around the world are devising multiple solutions for improving fuel economy and emissions while maintaining the high-performance multi-cylinder engines their customers have traditionally expected. One of the those solutions is cylinder deactivation.

Bentley already has two methods of cylinder deactivation on its 6.75-L and 4.0-L V8 engines but, as Rolf Frech, Member of the Board for Engineering, explained at the 2015 Geneva Motor Show, the complexity of the 6.0-L W12’s layout (essentially two narrow-angle V6s on a common crankshaft) and cylinder firing demanded a third solution.

“It was clear that we couldn’t use either of the solutions we currently employ as that would have demanded a new cylinder head," he said. "So we asked how can we do that with an intelligent arrangement?”

The challenge is that when cylinders are switched off they cool down, as does the catalytic converter, resulting in spikes of exhaust emissions. “The complication was to develop intelligent management just to switch the cylinders off and switch them back on with the right timing and change to the other six,” he said.

In essence, the engine control unit simply deactivates one bank of six cylinders while leaving the valves to operate as normal.

“The big advantage of this is not only about reducing CO2 on the normal test, but in daily use,” Frech explained. The significant gains are under part-throttle cruising conditions.

“If you make it into a real six-cylinder, you don’t have any problems with balance," he noted. "There was something of an issue with exhaust boom, but we have countered that with some modifications to the exhaust.”

By doing it in this manner, the inlet and exhaust sensors determine when to switch between each bank, ensuring the cylinders remain hot. It also fulfills U.S. OBD requirements.

The engine also receives a power increase, from 567 to 582 hp (423 to 434 kW), with rated torque also rising from 516 to 531 lb·ft (700 to 720 N·m). The greater output is accompanied by claimed improvements to fuel economy of up to 5% (combined fuel economy is 16.6 U.S. mpg) and lower CO2 emissions of 329 g/km.

Looking to future applications, Frech revealed that there would be “other opportunities” with W12-powered vehicles, including possible individual cylinder deactivation and electric-motor assistance for the forthcoming Bentayga SUV due later this year.

Author:
Sector:
Mentions:
Share
HTML for Linking to Page
Page URL
Grade
Rate It
4.00 Avg. Rating

Read More Articles On

2016-05-16
Powered exoskeletons, perhaps the ultimate in personal mobility, are no longer mere sci-fi/comic book fantasies. Hyundai/Kia is among the innovators working to reduce system cost in this exciting field.
2016-05-20
The first fruit of the latest Ford and GM join project on transmissions was unveiled recently, and it sure looks sweet. In this episode of SAE Eye on Engineering, Editor-In-Chief Lindsay Brooke looks at Ford and GM's new 10-speed automatic transmission.
2016-05-24
Mazda's new flagship SUV sheds significant weight with a high-strength steel intensive body structure, while introducing a new turbocharged 4-cylinder and improved interior.
2016-06-14
BWI Group believes its second-generation Magneto Rheological (MR) powertrain mount helps meet downsized-powertrain NVH challenges.

Related Items

Training / Education
2007-03-01
Training / Education
2009-12-15
Training / Education
2010-08-03
Technical Paper / Journal Article
2003-10-27
Technical Paper / Journal Article
2003-10-27
Training / Education
2010-03-15