Regan Brown
Active Fuel Management (AFM) is a technology developed by General Motors to improve fuel efficiency in V6 and V8 engines. It works by deactivating half of the engine's cylinders when full power is not required, such as during highway cruising, reducing fuel consumption and emissions without sacrificing performance. GM claims that AFM can improve fuel efficiency by up to 12%, although real-world figures reported by owners are closer to 5-7.5%. AFM is a cost-effective solution for customers as it does not require significant modifications to the engine. Vehicles known to have AFM include the 2005 Chevy TrailBlazer EXT, the GMC Envoy XL, Envoy XUV, and Pontiac Grand Prix.
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What You'll Learn
- Active Fuel Management (AFM) is a trademarked General Motors technology
- AFM improves fuel efficiency by deactivating half of the engine's cylinders
- GM vehicles with AFM technology can be identified by engine cover markings
- AFM lifters are smaller and lighter than standard lifters
- AFM is also known as cylinder deactivation or variable displacement
Active Fuel Management (AFM) is a trademarked General Motors technology
Active Fuel Management (AFM) is a technology developed and trademarked by General Motors (GM) to improve fuel efficiency in V6 and V8 engines. It does this by deactivating half of the engine's cylinders under light load conditions, such as highway cruising, reducing fuel consumption and emissions without sacrificing performance.
The basic premise of AFM is that most vehicle owners have more power than they need. Many consumers choose V-8 engines for driving performance or towing and hauling, yet during everyday driving, that powerful engine operates at a fraction of its capability, reducing engine efficiency and increasing fuel consumption. AFM saves fuel by using only half of the engine's cylinders during some driving situations and then seamlessly reactivating the other cylinders when a driver demands more power for acceleration, climbing a grade, or hauling.
The philosophy behind AFM is to increase fuel economy without reducing performance or resorting to force-induced smaller engines. GM claimed that the feature improved fuel efficiency by up to 12%, but owners have reported that the figure is closer to 5-7.5% in real-world conditions. The technology can be identified by specific engine block casting codes, engine cover markings, unique solenoids, and specific valve cover designs, among other visual indicators.
AFM is also known as cylinder deactivation or variable displacement and can be found on various GM engines, including the first-generation High-Feature V8 DOHC engine family and the 2005 Chevy TrailBlazer EXT. The Dynamic Fuel Management system is an advancement of AFM, using a DFM computer to make quick calculations to determine how many and which cylinders need to be deactivated to perform at optimum levels. This system can be found in newer vehicles, such as the 2021 Sierra 1500.
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AFM improves fuel efficiency by deactivating half of the engine's cylinders
Active Fuel Management (AFM) is a technology developed by General Motors (GM) to improve fuel efficiency in V6 and V8 engines. It works by deactivating half of the engine's cylinders under light-load conditions, such as highway cruising, to reduce fuel consumption and emissions without sacrificing performance. This technology can improve fuel efficiency by up to 12% without compromising the engine's power.
AFM is also known as cylinder deactivation or Displacement on Demand (DoD). It is designed to address the issue of large engines operating at a fraction of their capacity during everyday driving, resulting in reduced engine efficiency and suboptimal fuel economy. By deactivating half of the cylinders, AFM helps to optimise fuel usage and improve overall fuel economy.
In an eight-cylinder engine, AFM deactivates four cylinders, while in a six-cylinder engine, it deactivates three cylinders. This reduction in active cylinders leads to lower fuel consumption and, consequently, improved fuel efficiency. The system seamlessly reactivates the deactivated cylinders when more power is demanded by the driver, such as during acceleration or climbing a grade.
The process of cylinder deactivation in AFM is controlled by the engine control module (ECM), which monitors driving conditions and switches the cylinders on and off accordingly. This ensures that the engine maintains the necessary power while optimising fuel efficiency. Additionally, AFM is cost-effective for customers as it requires only a few new components, such as special valve lifters for the deactivated cylinders.
AFM has been implemented in various GM engines, including the GM Small Block Gen IV engine family, the first-generation GM EcoTec3 engine family, and the second-generation GM High-Feature V6 DOHC engine family. It has also been featured in vehicles such as the 2005 Chevy TrailBlazer EXT, the GMC Envoy XL, and the Pontiac Grand Prix.
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GM vehicles with AFM technology can be identified by engine cover markings
Active Fuel Management (AFM) is a trademarked technology from General Motors (GM) that improves fuel efficiency by shutting down half of the cylinders when the vehicle is operating under light-load conditions. This technology is also known as Displacement on Demand (DoD) or cylinder deactivation.
In addition to visual cues, there are other ways to identify if a GM vehicle has AFM technology. One of the easiest ways is to check the digital display on the dashboard, known as the Driver Information Center (DIC), which will indicate whether the engine is running as a 'V4' or a 'V8'. This information can also be found in the owner's manual, typically in the engine and powertrain sections, which will include descriptions, diagrams, and explanations of the AFM system.
AFM engines also have specific casting codes on the engine block that can be cross-referenced with GM technical documents or online databases. These codes are crucial for diagnosing and maintaining the vehicle as they help pinpoint issues within the system for precise diagnostics and repairs.
It is worth noting that some GM vehicles, such as the Buick Lacrosse and certain Chevy Silverado models, may not have AFM technology.
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AFM lifters are smaller and lighter than standard lifters
Active Fuel Management (AFM) is a technology that improves fuel efficiency in vehicles. It works by temporarily "turning off" half of the cylinders in a V6 or V8 engine when only a fraction of the engine's power is required to keep the vehicle moving. This technology was developed by General Motors (GM) and is trademarked by them.
When replacing a failed AFM lifter, it is critical to follow the correct procedure, as improper replacement methods can lead to further issues. In addition to the lifters themselves, the Valve Lifter Oil Manifold (VLOM) and the entire Displacement on Demand (DoD) oiling system must be maintained and checked for proper oil flow.
AFM lifters can fail due to various reasons, including oil supply issues caused by a malfunctioning or clogged VLOM, resulting in improperly timed activation and deactivation. To prevent these issues, it is essential to use Dexos-approved oil and maintain the oiling system regularly.
Some vehicle owners have expressed dissatisfaction with the AFM system, citing frequent lifter issues and high repair costs. There have been reports of lifters failing even with regular oil changes and proper maintenance. As a result, some owners have chosen to disable or delete the AFM system from their vehicles, opting for alternative solutions such as AFM disablers or delete kits.
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AFM is also known as cylinder deactivation or variable displacement
Active Fuel Management (AFM) is a technology developed by General Motors (GM) to improve fuel efficiency in vehicles without compromising performance or resorting to smaller engines. It is also known as cylinder deactivation or variable displacement.
AFM works by temporarily shutting down half of the engine's cylinders when the vehicle is in light driving conditions, such as highway cruising. This reduces fuel consumption as the engine is utilising only the required amount of power to keep the vehicle moving. When more power is demanded by the driver, for instance during acceleration or when climbing a grade, the deactivated cylinders are reactivated seamlessly.
The system uses a combination of simple hydraulic valves and sophisticated software to switch off the cylinders when the driver does not need full power. A solenoid system is used to collapse the valve lifters, reducing pumping losses and improving fuel efficiency. This technology is cost-effective for customers as it only requires special valve lifters for the cylinders that are deactivated.
AFM was first introduced as Displacement on Demand (DoD) and was subsequently renamed Active Fuel Management. It has been featured in several GM vehicles, including the 2005 GMC Envoy XL, Envoy XUV, and Chevrolet TrailBlazer EXT, as well as the 2011 Holden Calais V V8 AFM VE Series II. In 2018, GM announced an improved version of AFM called Dynamic Fuel Management, which can shut off any number of cylinders in various combinations, maximising fuel economy and avoiding switching between banks of cylinders.
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Frequently asked questions
Active Fuel Management (AFM) is a technology developed by General Motors to improve fuel efficiency in V6 and V8 engines. It does this by deactivating half of the engine's cylinders under light load conditions, such as highway cruising, reducing fuel consumption and emissions without sacrificing performance.
You can check the owner's manual or look for the AFM badge on the engine and AFM lifters in cylinders 1, 4, 6, and 7. You can also look for the V4 symbol or AFM light on the dashboard, or check for engine cover markings, unique solenoids, and specific valve cover designs.
Active Fuel Management is a trademarked technology of General Motors, so it is found in various GM engines. This includes the 2005 Chevy TrailBlazer EXT, the GMC Envoy XL, the GMC Envoy XUV, and the Pontiac Grand Prix.
