General Motors Dynamic Fuel Management Cylinder Deactivation Technology
Dynamic Fuel Management (DFM), otherwise known as Dynamic Skip Fire, is a General Motors engine technology that shuts down the engine’s cylinders to optimize power delivery and efficiency. DFM is an improvement to Active Fuel Management, which it succeeds.
The philosophy behind Dynamic Fuel Management (DFM) is the same as it was for its Active Fuel Management (AFM) predecessor: to increase fuel economy while not reducing performance or resorting to force-inducted smaller engines.
A basic premise of DFM as well as AFM is that most of the time, drivers have more power than they need in their vehicles. Many consumers choose V-8 engines for driving performance or towing and hauling, but during everyday driving, that powerful engine operates at a fraction of its capability, which reduces engine efficiency and results in less-than-optimal fuel economy.
As such, Dynamic Fuel Management saves fuel by only using the cylinders of an engine that are required during the specific driving situation – such as highway cruising. It then seamlessly reactivates the other cylinders when a driver demands more power for acceleration, climbing a grade or hauling.
In speaking about Active Fuel Management, GM’s global chief engineer for small block engines, Jordan Lee stated the following: “Rather than adding turbochargers or multi-valve cylinder heads to increase the power of smaller engines, we chose to keep the proven capability of our larger V-8 truck engines, and save fuel by switching off half of the cylinders when they aren’t needed.”
How It Works
Dynamic Fuel Management is powered by a sophisticated controller that continuously monitors every movement of the vehicle’s accelerator pedal and runs a complex sequence of calculations to determine how many cylinders are required to meet the driver’s requested torque. The Dynamic Fuel Management computer can make this determination 80 times per second.
An electromechanical system deactivates and reactivates all 16 of the engine’s hydraulic valve lifters, controlling valve actuation. The system uses solenoids to deliver oil pressure to control ports in the lifters, which activate and deactivate the lifters’ latching mechanisms.
When a cylinder is deactivated, the two-piece lifters effectively collapse on themselves to prevent them from opening the valves. When the cylinder is reactivated, solenoids send an oil pressure signal to the control ports on the lifters and the latching mechanism restores normal function, allowing the valves to open and close.
This industry-first cylinder deactivation technology enables the engines to operate in 17 different cylinder patterns to optimize power delivery and efficiency.
“The increased variability of Dynamic Fuel Management means the engine will operate more often with a reduced number of cylinders, which saves fuel across the board,” said Jordan Lee, chief engineer of GM Small Block engines. “Better yet, the transitions are transparent, and because the system is torque-based, you’ve always got that satisfying feeling of power on demand that comes from GM’s Gen V Small Block V-8 engines.”
The primary benefit of Cylinder Deactivation/AFM is better fuel economy without downsizing engines, decreasing power, adding turbo-chargers or using a Dual OverHead Cam (DOHC) engine design.
Dynamic Fuel Management can also be referred to as:
- Dynamic Skip Fire (DSF)
- Cylinder Deactivation
- Displacement on Demand (DoD)
Dynamic Fuel Management succeeds Active Fuel Management, which is a related but different technology.
Dynamic Fuel Management vs. Active Fuel Management
General Motors first introduced its Active Fuel Management cylinder deactivation system in 2005. According to Lee, “Dynamic Fuel Management is a natural progression of the technology.”
Lees states that Dynamic Fuel Management “enables only the cylinders needed to deliver the power you want, seamlessly delivering the best balance of power and fuel economy.”
Compared to Active Fuel Management, which alternates between eight- and four-cylinder modes, DFM features 17 cylinder patterns. That greater authority over cylinder patterns constantly to optimize efficiency and power delivery at all speeds.
During an industry-standard test schedule, the 2019 Silverado 1500 2WD with the 5.3L L84 L84 engine and DFM operated with fewer than eight active cylinders more than 60 percent of the time, 9 percent more than a comparably equipped 2018 Silverado with Active Fuel Management.
Dynamic Fuel Management is currently available on the following General Motors engines:
Dynamic Fuel Management is currently available in the following General Motors vehicles:
- 2020 Escalade
- 2020 Escalade ESV