Two unique propulsion technologies may be the best solution for reducing carbon dioxide emissions, matching diesel for emissions compliance, performance and cost.
On the path to electrification, Delphi engineers combined two technologies, Dynamic Skip Fire (DSF) and 48-volt, mild hybrid, in a prototype Volkswagen Passat with a 1.8-liter engine, which reduced carbon dioxide emissions by 13 percent.
DSF, developed by Delphi and its partner company, Tula Technology, of San Jose, Calif., matches the number of cylinders that fire to the work being demanded of the engine. When using cruise control on the highway, it’s possible to go stretches without any cylinders firing. Yet, when the driver needs all four cylinders to fire, he or she instantly has all the power the 170 horsepower four-cylinder engine can generate.
DSF is much more than cylinder deactivation, which in a four-cylinder engine, only alternates between four cylinders and two cylinders, and can be plagued by noise, vibration and harshness. DSF can fire 0-, 1-, 2-, 3- or 4-cylinders, depending on the torque and power required. In the prototype VW Passat with DSF, a driver can’t hear or feel any roughness. And the big bonus – the carbon dioxide emission reductions are substantial.
While DSF performs best at cruising speeds, the 48-volt, mild hybrid captures energy typically lost while braking and then uses that energy to boost the engine at launch and during some acceleration, while simultaneously reducing CO2 emissions.
“It’s all about electrifying vehicles,” says Mary Gustanski, vice president of engineering for Delphi. “If you look at what’s in the news, what the automakers are talking about and what even the countries are saying — it’s that they want to get to zero emission vehicles.
“How are you going to get more electric vehicles on the road? You have to start by electrifying, which means adding some portion of assistance for your internal combustion engines so that they operate more efficiently, improving fuel economy and reducing emissions.”
Car companies are adding mild hybrids, full hybrids and plug-in hybrids – creating electrified vehicles – in increasing numbers. For the powertrain community, that path to electrification will shape the next 20 to 30 years. The transition will not happen overnight. Until that time, combining DSF with 48-volt, mild-hybrid technology is a cost effective start.