Fully variable valvetrains make cylinder deactivation simple add-on for OHC 4-cyl. engines.
Cylinder deactivation, a fuel-saving technology that has made V-8-powered pickups and SUVs more palatable for economy-minded buyers, is on the brink of resurgence.
With a corporate average fuel economy mandate of 35.5 mpg (6.6 L/100 km) taking effect in 2016, the two primary suppliers of electronically controlled cylinder-deactivation (CD) systems each tell Ward's they have about 20 programs in the works with OEM customers.
Together,Corp. and the Group's INA division say they expect about 12 of those to reach production within the next three years. New V-8s are scarce among the likely prospects.
“Everybody's interested in cylinder deactivation,” says Bob Zito, director-engineering for engine components atGroup USA Inc.
“There's more money going into the powertrain for fuel economy these days than there was 10 years ago,” says David Genise, director of engineering-valvetrain at's Vehicle Group, which manufactures 300 million engine valves annually.
Moving the technology is the trend toward smaller engines. Since 2004, CD has been heavily employed in OHV V-8s fromCo. and Group LLC for pickups, SUVs and cars.
GM says it has more than 2.7 million vehicles on the road globally with CD. In North America,has produced 827,000 CD V-8s for vehicles sold in the U.S. since 2004.
Motor Co. Ltd. also has the technology on a 3.5L SOHC V-6 and on 4-cyl. engines in hybrid applications.
The wave of new programs from Eaton and Schaeffler are focused on overhead-cam engines, mostly of the 4-cyl. variety.
For years, multi-valve dual overhead-cam engines were considered poor candidates for CD because they were twice as expensive — requiring twice the hardware — when compared with OHV engines.
That's one reasonMotor Co., which has few OHV engines, has no CD programs in production, nor any planned.
But smaller engines make the cost differential less onerous, and new technologies are quelling some of the vibration issues associated with small-displacement engines.
Plus, the CD penetration rate is spurred along by mandates in the U.S. and elsewhere requiring higher fuel economy.
“If you look at fuel prices going up, it makes cylinder deactivation a salable point. Those two go hand in hand,” Eaton's Genise says.
The technology idles unneeded cylinders during light-load driving cycles, generally boosting fuel economy up to 12%.
Eaton's CD system in GM's 5.3L V-8 — a contract shared withCorp. — is marketed as Active Fuel Management.
Half the cylinders have unique 2-piece valve lifters, which incorporate two telescoping sections that can collapse into one another. An oil-pressure-activated locking pin in the lifters is engaged or disengaged based on driving conditions.
To deactivate half the cylinders, hydraulic pressure is used to unlock the pin, enabling the valve lifters' two sections to freely telescope into one another. As a result, camshaft motion is not translated to the pushrod, meaning intake and exhaust valves remain closed, until a throttle input causes them to reopen.
Looking forward, GM has hinted the 1.4L DOHC turbocharged I-4 in the new Chevrolet Cruze will offer AFM.
For Chrysler's Multi-Displacement System on the 5.7L Hemi V-8, INA manufactures specially designed valve lifters that can selectively decouple the cam lift event from the respective poppet valves via electro-hydraulic actuation.
For new, high-revving OHC engines, Eaton and Schaeffler are introducing valvetrains that can operate with more variability, including CD if desired.
Eaton says its new variable valve-lift system can improve both fuel economy and power delivery, simply by switching valve-lift profiles. Combined with existing cam-phaser technology, for instance, the system can improve fuel economy up to 7%.
The technology switches modes the same way as the CD rocker arm and can be interchangeable, enabling different engines for diverse markets merely by changing the valvetrain components.
Zito says full variability of the valvetrain is the better route to achieve CD, while getting better performance and fuel economy, without a huge cost premium.