Delphi39s DSF in operation Circles at center of screen show active green and inactive white cylinders

Delphi's DSF in operation. Circles at center of screen show active (green) and inactive (white) cylinders.

Delphi Touts 48V/DSF System as Inexpensive Diesel Alternative

The supplier’s combination of a super-smart cylinder deactivation system with advanced mild-hybrid technology works seamlessly in a 1.8L Volkswagen Passat test vehicle and promises big gains in fuel-economy ratings and emissions reduction.

TROY, MI – Battery-electric vehicles may dominate the landscape someday, but it’s the transition between then and now that is capturing much of the focus at supplier Delphi.

“How are you going to get more electric vehicles on the road?” Mary Gustanski, vice president-engineering/program management, says here at a media backgrounder on Delphi’s latest powertrain developments. “You have to start by electrifying, which means adding some portion of assistance for your internal-combustion engines so that they operate more efficiently.”

Even if BEVs account for 30% of the global fleet by 2030 – considered an aggressive forecast, it means 70% of new vehicles sold worldwide still will have some form of internal-combustion engine, she points out, suggesting advanced IC technology will have a long and dominant role in engineering the transition to an all-EV future.

In May, Delphi announced it was splitting into two companies, spinning off its long-core powertrain operations from its electronics business that is tilted toward the future hotbeds of infotainment, advanced driver-assistance systems and fully autonomous vehicles.

That led to speculation the supplier was looking to wind down its involvement in powertrain, a theory quickly disputed by Delphi officials and backed up here in a presentation around the supplier’s latest technology.

Among the advanced systems at the heart of Delphi’s future-powertrain play is Dynamic Skip Fire cylinder-deactivation, which the supplier says could improve fuel efficiency of a 4-cyl. engine up to 8% at a relatively low wholesale cost of about $350.

A joint project with Silicon Valley software developer Tula Technology, DSF is a considerable step up from current cylinder-deactivation technology on the market. Today’s systems shut down a fixed set of cylinders based on rigid operating conditions, but DSF can shut off any or all cylinders at any time for optimum fuel efficiency.

Utilizing the technology would require an automaker to modify the head of an existing engine to accommodate the extra hardware that includes special sensors and Delphi’s roller finger followers that deactivate valve operation to shut down each cylinder as needed.

For testing purposes, Delphi fitted the system to a Volkswagen Jetta equipped with the automaker’s EA888 1.8L turbocharged gasoline engine. In a test drive here of the car fitted with a special display screen to monitor its performance, the engine rapidly activates and deactivates cylinders as needed, switching to one, two or three cylinders when the speed and terrain allow the driver to go light on the throttle, and back to all four cylinders when more power is needed. During coast-down, with the driver’s foot completely off the throttle, all cylinders are deactivated.

The firing patterns appear random, and the switch from zero- to four-cylinder operation and back happens in a fraction of a second. There’s no discernable NVH penalty with use of the system in the experimental Jetta. Delphi says the technology can vary the combination of cylinders firing up to 6,000 times per minute at 3,000 rpm on a 4-cyl. engine and twice that on an 8-cyl.

However, the technology’s advantages really shine in another test car here, a VW Passat equipped with the same 1.8L engine but fitted with both DSF and Delphi’s 48V mild-hybrid system.

With the 48V system allowing the engine to fully shut down at stops and restart smoothly, plus supplying bursts of electrical power when more torque is needed, the DSF system appears to become even more active and beneficial. With the two technologies in combination, Delphi says it is achieving 19% fuel-economy gains in EPA-cycle city driving compared with the standard Passat 1.8L.

That’s an improvement from the 10%-15% fuel-efficiency increase the supplier says to expect from application of its 48V mild-hybrid technology alone, which it says would cost about $1,000 to automakers.

Part of the advantage in combining the two technologies comes from the reduction of pumping losses. As DSF deactivates a cylinder, it stops pumping, meaning there’s less engine braking during deceleration. That forces the vehicle’s braking system to carry more of the stopping load. That braking energy then can be recaptured by the starter-generator to charge the 48V system’s lithium-ion battery, electricity that can be used later for added boost when extra torque is needed. In return that reduces the demand for power from the gasoline engine, allowing it to run more efficiently.

“I like to say ‛One plus one equals more than two when it comes to Delphi’s electrified solutions,’” Gustanski says.

Pairing the two technologies would put gasoline engines nearly on par with diesels in fuel economy and carbon-dioxide emissions, Delphi says. Cost to automakers for the 48V/DSF technology combined is pegged at about $1,500, which Delphi says is about 25% less than a comparable diesel when the need for diesel aftertreatment systems is factored into the equation.

“Now European automakers have a story for customers about how they can replace their diesel,” Gustanski says, noting policymakers in the U.K., France and Germany appear to be moving toward diesel bans. “Will it happen? I don’t know, but I think consumer confidence in diesels has weakened.”

DSF will work on engines both larger and smaller than the VW 1.8L, officials say, indicating application for V-6 and V-8 engines is relatively easy compared with a 4-cyl. and yields more than 15% improvement in fuel economy. Delphi earlier demonstrated the system in 2015 on a GMC Yukon Denali powered by a V-8. The supplier says it is hoping to develop the technology for 3-cyl. engines as well, though that work has not been started.

DSF is ready for production and is in development with several customers, Delphi says, but there are no production programs as of yet. Gustanski estimates applications won’t come before 2019-2020. She says Delphi has pitched the technology to Department of Transportation officials as one way automakers might meet future CAFE targets, set for 54.5 mpg (4.3 L/100 km) in 2025 but now set to undergo another midterm review later this year. Automakers are pushing for some relaxation in those standards as a result of low gasoline prices that are driving consumers toward less fuel-efficient vehicles.

Delphi’s 48V system is expected see application in production models later this year.

There’s no indication from the supplier when the two technologies might see action together in a production vehicle.

[email protected] @DavidZoia

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