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On the Right Track

Delphi variable valve train technology is helping vehicle manufacturers enhance engine efficiency to boost fuel economy while reducing emissions, without sacrificing performance.

Hidden deep inside any engine are valve train components that, while small, can make a big impact on performance as well as fuel economy and emissions reduction. Delphi is positioned to help manufacturers achieve those highly desirable attributes with a portfolio of valve train products that can meet the needs of virtually any powertrain system.

Long a leader in conventional valve train technologies, Delphi is now developing advanced variable valve train products. Its growing lineup includes variable valve timing and variable valve lift products designed to help enhance engine efficiency.

"When combined with Delphi's gasoline fuel systems, these variable valve systems are proven to be a cost-effective method to help significantly improve the combustion process," said Paul Van Heyningen, chief engineer, valve train, Delphi Powertrain Systems. "That means engine efficiency is increased, without the costs associated with other powertrain technologies. That efficiency yields greater fuel economy, which in turn results in reduced CO₂ emissions, a critical target area even as manufacturers strive to meet increasingly stringent emissions standards around the world."

Helping achieve compliance with these standards will be welcome news for manufacturers. Even better, they won't have to compromise on engine performance as much as they might with other fuel-efficiency-enhancing technologies on the market.

"Fuel economy gains obtained through the use of variable valve actuation will by definition impact performance to a certain degree," said Van Heyningen. "But Delphi technology does help minimize the impact, enabling manufacturers to maintain vehicle character as much as possible."

Delphi's cylinder deactivation is an excellent example of this benefit, pointed out Vishy Seetharaman, manager, global powertrain marketing, Delphi Powertrain Systems.

"With our advanced cylinder deactivation system, a driver can enjoy V8 performance when acceleration is necessary, and yet under certain driving conditions half the engine's cylinders are electronically deactivated to significantly boost fuel economy," Seetharaman explained. "And the transition from one mode to the other is so smooth it's actually transparent to the driver."

Variable Valve Timing


	Delphi Cam Phaser and Oil Control Valve

Delphi's variable valve timing technology is centered on its variable cam phasing technology. By changing intake or exhaust (or both) valve timing as engine operating conditions change, this technology helps engines optimize efficiency based on current operating parameters.

"By making these incremental adjustments, variable valve timing technology helps improve fuel economy and reduce CO₂ emissions, all at a relatively low cost," said Van Heyningen. "The system can be fine-tuned to help maintain desired performance targets as well."

In fact, variable valve timing can generate a noticeable fuel economy improvement. Variable valve timing also offers proven benefits of improved low speed torque and peak power.

Delphi's variable valve timing portfolio includes:

Variable Cam Phasers: Can be used to shift the intake cam, the exhaust cam, or both on dual overhead cam engines to help increase engine efficiency and improve idle stability, while helping the engine deliver more torque and horsepower.
Oil Control Valve: Controls oil flow to the cam phaser to help maintain desired valve timing.


	Delphi's Cylinder Deactivation for Overhead Valve Engines includes a Lifter Oil Manifold Assembly and a Lifter Guide Assembly

Variable Valve Lift

Delphi's variable valve lift products help change the timing, duration, and lift when opening and closing intake and/or exhaust valves for maximum engine efficiency. The systems are controlled by Delphi software, which enables a broad range of functionality.

"By varying valve lift and duration based on engine load, overall pumping work is minimized, resulting in enhanced efficiency," said Van Heyningen. "For a relatively low investment, manufacturers can realize tremendous benefits."

These benefits can include up to 10 percent improvement in fuel economy, as well as boosts in low-speed torque and peak power—all while reducing CO₂ emissions. And the technology also helps enable E85 flex fuel optimization and homogeneous charge combustion ignition combustion schemes.

Delphi's variable valve lift portfolio includes:

2-Step Valve Lift System: Switches between high and low lift cam profiles via finger follower lift modes to provide two-step valve lifting in type 2 valve trains, enabling fuel economy savings up to 6 percent.
Continuously Variable Valve Lift: Currently under development, Delphi Continuously Variable Valve Lift is designed to provide continuously variable valve lift profiles between zero and full lift by rotating a control shaft using a DC motor-driven actuator, enabling greater flexibility in engine combustion by de-throttling and increased dilution capability, resulting in a fuel economy improvement of up to 10 percent.
Cylinder Deactivation: Deactivates a select number of cylinders during light load operation. This is accomplished by decoupling intake and exhaust valves from the cam lobe motion by a deactivation roller hydraulic valve lifter in Delphi's Cylinder Deactivation for Overhead Valve Engines. In overhead cam type 2 engines, deactivation is accomplished through either a deactivating hydraulic lash adjuster or a deactivating roller finger follower, which were both introduced by Delphi.


	Delphi Heavy Duty Roller Hydraulic Valve Lifter

A Global Leader

Delphi's valve train expertise dates to 1947, with the development of the hydraulic lifter. Ever since, Delphi engineers have continued to develop advanced solutions, including today's electro-hydraulically controlled valve train products. In addition to the advanced variable valve timing and variable valve lift products, Delphi offers a number of conventional valve products, including:

While its lineup of individual components is impressive, Delphi's strength can be especially remarkable in the development of an integrated system.

"Our complete understanding of the combustion process enables us to develop intelligent options throughout the powertrain," said Seetharaman. "We can also help our customers design control algorithms in order to optimize the systems, helping them achieve desired levels of performance and fuel economy, while complying with emissions standards."

And with a global application and manufacturing footprint, including sites in the Europe, Asia, and the United States, Delphi is positioned to supply many of the leading vehicle manufacturers worldwide.

For more information about Delphi's valve train technologies, click here.