A new day is dawning for cylinder deactivation.
The technology that idles unneeded cylinders in V-6s and V-8s during light-load driving cycles had been shelved after General Motors Corp. engines so equipped in the 1980s performed miserably.
But over the past several years, as the popularity of big engines collides with volatile fuel prices, cylinder deactivation has become increasingly attractive for auto makers eager to boost the fuel economy of their fleets without upsetting demand for large-displacement engines or adding significantly to vehicle prices.
Overnight, cylinder deactivation has gone from a far-out technology with a tarnished history to a readily available engine feature for high-volume cars and trucks, for little extra cost to consumers.
Two of the most popular V-8s in the U.S. — General Motors Corp.'s 5.3L and Chrysler Group's 5.7L Hemi — now feature the modern interpretation of electronically controlled cylinder deactivation, which can boost fuel economy between 8% and 20%, depending on the test cycle.
Chrysler was first to market in 2004 with modern cylinder deactivation, marketed as Multi-Displacement System (MDS) on the 300C and Dodge Magnum RT.
Today, MDS is standard on nearly all Hemi-powered vehicles. Chrysler says it expects to have nearly 1 million MDS-equipped vehicles on the road by 2007.
Not to be outdone, GM says it will have 15 vehicles on the road in '07 featuring its similar cylinder deactivation technology, Active Fuel Management (AFM).
By 2008, GM says it will have 2 million AFM-equipped vehicles on the road.
Not bad, considering all this volume is derived from overhead-valve engine architectures, which are easily outnumbered in the U.S. by overhead-cam mills.
Applying cylinder deactivation to OHC engines is harder and more expensive than on OHV setups, but it is possible, says James Westbrook III, manager-Valvetrain Systems for INA Engine Components, part of Schaeffler Group USA Inc.
INA supplies the deactivating valve lifters for Chrysler's MDS, while Eaton Corp. and Delphi Corp. produce deactivating lifters for GM's 5.3L V-8 with AFM.
INA has several active cylinder deactivation projects under development for OHC mills, Westbrook tells Ward's. “It is expected that these products will come to market in the next few model years in the North American market,” he says.
Westbrook admits adapting cylinder deactivation to OHC engines is more difficult. “But the challenges are being overcome with each subsequent development phase,” he says.
The issues are cost and complexity. Pushrod OHV engines generally have two valves per cylinder, while more modern OHC mills typically have four valves per cylinder. For MDS, INA manufactures special valve lifters that can selectively decouple the cam lift event from the respective poppet valves (for both intake and exhaust ports) via electro-hydraulic actuation.
INA has produced more than 22 million MDS lifters since late 2003.
Each Hemi has eight MDS lifters — one for each valve on four of the eight cylinders — and they are expected to cost about $10 to $12 a piece, based on industry estimates. A standard lifter costs an OEM between $2 and $3 apiece, sources say.
MDS also requires four solenoids — one for each cylinder to be shut down — costing about $4 to $7 apiece. Add it up and subtract the eight standard lifters that are replaced, and Chrysler's cost for these MDS components is between $72 and $108.
Applying cylinder deactivation to 16 valves on an OHC V-8 would cost an OEM about $160 to $180 for the lifters, excluding the cost of the solenoids or the added engineering necessary, sources say.
Honda Motor Co. Ltd. already supplies its own cylinder deactivation system on three SOHC engines available in the U.S.: the 1.3L 4-cyl. in the Civic Hybrid, 3.0L V-6 in the Accord Hybrid and 3.5L V-6 in the Odyssey and Pilot.
Ford Motor Co., which uses OHC architectures almost exclusively, has been lukewarm to cylinder deactivation.
Ford officials recently told Ward's the technology has little value in real-world driving, and that the auto maker has no immediate plans to implement it.
One drawback is the duty cycle for cylinder deactivation. Under heavy engine loads, during towing, for instance, power from all cylinders is essential. The technology also doesn't function at idle. Chrysler's MDS operates only at vehicle speeds over 18 mph (29 km/h) and between engine speeds of 1,000 and 3,000 rpm.
Still, Chrysler says the Hemi with MDS operates in V-4 mode 40% of the time in city driving and 90% of the time on the highway, according to Federal Test Procedure driving cycles.
Chrysler estimates MDS, because of its widespread use in the Hemi, will save 60 million gallons (227 million L) of fuel annually by the end of 2007, based on 15,000 miles (24,139 km) per year.
For the immediate future, INA remains focused on its current OHV cylinder deactivation programs. In addition to the Hemi, INA supplies cylinder-deactivating lifters for GM's latest 3.9L OHV V-6 (two valves per cylinder) for the Impala sedan.
INA's plant in Cheraw, SC, has been producing the GM lifters since April. The plant can manufacture deactivating lifters for more than 1 million engines but, to date, is well under capacity.
The 3.9L with AFM is an upgrade from the standard 3.5L OHV V-6.
GM also has a 3.0L V-6 with AFM in China that debuted in the Buick LaCrosse in the second quarter. The engine uses the same cylinder-deactivation components as the 3.9L. GM says there currently are no plans to bring this engine to the U.S.
GM also has shown a prototype cylinder-deactivation system for OHC architectures but has yet to fit any of its production OHC engines with the technology.
Meanwhile, INA produces its deactivating lifters for the Hemi at its plant in Hirschaid, Germany; the Hemi is built in Saltillo, Mexico. DaimlerChrysler has requested INA increase its capacity for MDS lifters, and the supplier says it has complied, without giving details.
Chrysler also has a high-performance 6.1L version of the Hemi, but the auto maker says the larger mill's unique calibration makes it incompatible with MDS.
Cylinder deactivation does not fit every engine, INA's Westbrook admits. “If the vehicle is too heavy for a particular powertrain, then the drive cycle and engine loading wouldn't allow for a high frequency of cylinder deactivation,” he says.
However, for V-6s and V-8s, most steady-state power requirements easily accommodate the technology, which can help auto makers meet corporate average fuel economy numbers, he says.
As V-6s grow larger, Westbrook says it is reasonable to expect cylinder deactivation to become more common.
