Dynamic Skip Fire & Other Tricks Give 2019 Silverado Better Mileage
Silicon Valley software company Tula Technology develops advanced cylinder deactivation strategy.
There has been tons of news recently, coming out of the Detroit Auto Show and elsewhere, about the next generation Chevy Silverado pickup truck due in 2019. Besides the new 3.0 liter straight six diesel engine, there is a new, advanced, cylinder deactivation technology that is said to deliver a 15% or greater improvement in real-world fuel economy. A Silicon Valley company called Tula Technology, purchased by GM in 2012, has developed a sophisticated computer system that can predict and control deactivation of up to seven of the eight cylinders.
Ford famously went to an aluminum construction on the current F-150 in the name of weight savings and fuel economy. Chevy, who famously made fun of the aluminum bed, managed to cut nearly 500 lbs from the new truck, using steel everywhere but the doors, hood, and tailgate. The tough looking and slightly bigger body of the Silverado was whittled by the wind tunnel to be 7% more aerodynamic than the previous outgoing model, using every trick in the book.
Dynamic Fuel Management
The current Silverado already has the ability to shut down 4 cylinders when cruising at low loads, but the Dynamic Fuel Management on the 2019 edition can shut down up to 7 of the 8 cylinders. The Tula Technology system uses much more powerful processors and algorithms to anticipate how much of the engine needs to be active. The rocker arms have a device that allows them to pivot without opening the valve, trapping air in the cylinder as a spring.
It seems strange, but engines are at their most efficient at large throttle openings, which is one of the reasons a diesel engine which has no throttle plate is more efficient. Between shutting down cylinders, and opening the throttle by wire, the computer can run the motor making just enough power as you need. Delphi and Tula produced a video that explains it much better.
Cruising down the freeway at 60 mph, most trucks only need 30-50 horsepower. They can make by working hard to suck air through a tiny throttle opening into all eight cylinders. The new system shuts down six or seven cylinders, opens up the throttle, and suddenly your 6.2 liter motor is just 1.5 liters, but still with most of the smoothness of a V8. Come to a hill or step on the gas, and more cylinders light off within one of two revolutions of the motor, or about a hundredth of a second.
Currently, the Silverado also has eAssist, with a 13 horsepower/44 lb-ft electric motor running through the engine accessory drive. This allows regenerative braking to recover energy, adds a little power when accelerating flat out, and runs the AC when the engine shuts down at a stop. There is no word yet if the next generation will use this mildest of hybrid systems, or possibly try one more time with a full hybrid truck. Both Ford and Ram have plans for hybrid versions of their trucks in the near future.