What is afm on gm 5.3?
Active Fuel Management (formerly known as displacement on demand (DoD)) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests shows a 5.5–7.5% improvement in fuel economy.
GM's Active Fuel Management technology used a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine.
GM used the Active Fuel Management technology on a range of engines including with the GM Small Block Gen IV engine family; First-generation GM EcoTec3 engine family; Second-generation GM High-Feature V6 DOHC engine family; and First-generation High-Feature V8 DOHC engine family. Vehicle applications included the 2005 Chevy TrailBlazer EXT, the GMC Envoy XL, Envoy XUV and Pontiac Grand Prix.
General Motors was the first to modify existing, production engines to enable cylinder deactivation, with the introduction of the Cadillac L62 "V8-6-4" in 1981.
In 2004, the electronics side was improved greatly with the introductions of Electronic Throttle Control, electronically controlled transmissions, and transient engine and transmission controls. In addition, computing power was vastly increased. A solenoid control valve assembly integrated into the engine valley cover contains solenoid valves that provide a pressurized oil signal to specially designed hydraulic roller lifters provided by Eaton Corp. and Delphi. These lifters disable and re-enable exhaust and intake valve operation to deactivate and reactivate engine cylinders . Unlike the first generation system, only half of the cylinders can be deactivated. It is notable that the second generation system uses engine oil to hydraulically modulate engine valve function. As a result, the system is dependent upon the quality of the oil in the engine. As anti-foaming agents in engine oil are depleted, air may become entrained or dissolve in the oil, delaying the timing of hydraulic control signals. Similarly engine oil viscosity and cleanliness is a factor. Use of the incorrect oil type, i.e. SAE 10W40 instead of SAE 5W30, or the failure to change the engine oil or oil filter at factory recommended intervals, can also significantly impair system performance.
In 2001, GM showcased the 2002 Cadillac Cien concept car, which featured Northstar XV12 engine with Displacement on Demand. Later that year, GM debuted Opel Signum² concept car in Frankfurt Auto Show, which uses the global XV8 engine with displacement on demand. In 2003, GM unveiled the Cadillac Sixteen concept car at the Detroit Opera House, which featured an XV16 concept engine that can switch between 4, 8, and 16 cylinders.
On April 8, 2003, General Motors announced this technology (now called Active Fuel Management) to be commercially available on 2005 GMC Envoy XL, Envoy XUV and Chevrolet TrailBlazer EXT using optional Vortec 5300 V8 engine. GM also extended the technology on the new High Value LZ8 V6 engine in the Chevrolet Impala and Monte Carlo as well as the 5.3L V8 LS4 engine in the last generation Chevrolet Impala SS, Monte Carlo SS and Pontiac Grand Prix GXP. In both designs, half of the cylinders can be switched off under light loads.
On July 21, 2008, General Motors unveiled the production version of the 2010 Chevrolet Camaro. The Camaro SS with an automatic transmission features the GM L99 engine, a development of the LS3 with Active Fuel Management which allowed it to run on four cylinders during light load conditions.
In January 2018, GM announced an improved version of AFM called Dynamic Fuel Management to be initially released in Chevy Silverado trucks. This system shuts off any number of cylinders in a variety of combinations, maximizing fuel economy and avoiding switching between banks of cylinders . The system is based on Dynamic Skip Fire, a technology developed by California company Tula Technology. The 6.2L V8 engine of the Chevrolet Silverado incorporating the technology was named one of Ward's 10 Best Engines for 2019.
GM Expands Deployment of Displacement on Demand
I purchased a CPO 2017 Suburban LS about a year ago with ~70K on the clock..
Over the summer the transmission gave up the ghost and it was replaced under the CPO warranty.
Now at ~88K the vehicle was stricken with the dreaded lifter failure “dead misfire on cylinder 7” as related to the AFM and the dealer replaced the left side valve lifters.
Fingers crossed that everything is GTG now (but if not, “please let it fail within the next year.”).
My question is –
Would it be prudent to purchase an AFM disabler at this point to preserve the new lifters and maybe prevent the right side lifters from failing?
Not purchase the AFM disabler so if the right side is going to fail it will fail within the next year and the CPO warranty will cover it?
Thank you in advance!!
AFM is good for gas mileage and can be 5-7 percent more fuel-efficient under certain conditions.
There are a few reasons:
There are two ways to disable or delete Active Fuel Management on your GM or Chevy Gen IV LS or LS-based Vortec engine—one is to install an AFM Disabler, and the second is to install an AFM Delete Kit. Here’s what you need to know:
An AFM Delete Kit is recommended when an AFM lifter fails or when doing performance upgrades. It replaces the AFM components with standard parts.
When installing an AFM delete kit:
An AFM Disabler is an electronic device that plugs into the OBD-II port, under the dashboard. It prevents the computer from switching over to four-cylinder mode. It’s a simple and effective way to turn off the AFM system and provides the added bonus of improving exhaust sound.
NOTE: A disabler device should ONLY be used if the valvetrain is in good working order. We do not recommend this.
Engines with AFM use a high-volume oil pump. When you eliminate the AFM system, the extra oil is no longer needed. Excess oil will be pushed out of the pressure relief valve into the oil pan. This will spray oil on the bottom of the cylinder walls which can cause oil burning, especially in high-rpm engines.
NOTE: Once you install a DOD/AFM delete kit you must tune the vehicle. Not doing so will cause the vehicle to revert to 4 cylinder mod.
AFM engines use special lifters for cylinders 1, 4, 6, and 7. They are taller and have special oil holes.
Engines with AFM also use a special camshaft, a high-volume oil pump, and a pressure relief valve in the oil pan.
When engine load is low:
Since no air can get in or out, four cylinders provide no power. The engine is running on only four cylinders.
Active Fuel Management (AFM) was a system GM engineers developed back in 2005 to help improve the fuel mileage from some of their V6 and V8 engine applications. AFM shuts off half of your engines cylinders to operate at a reduced power level to reduce fuel consumption when running in low load and cruise situations. By 2019, GM had developed Dynamic Fuel Management (DFM) which a smarter version of AFM. While AFM would shut-off the same cylinders every time the system would activate, with DFM, the engine has up to 17 different patterns it can run in depending on load and other inputs. With DFM, the engine can turn off two cylinders, four cylinders, or any of the eight it sees necessary to meet the current situation and demand.
Popular vehicles where you'll find AFM/DFM
On paper and even in the real world, AFM and DFM has shown some benefits when it comes to improved fuel mileage and GM has been able to claim 5-7% increases directly correlated to AFM. There have been studies held that back the claims with data and vehicle owners can attest to seeing solid mileage from their GM V6 and V8 engines, especially when compared to that vehicles counterpart from another brand. However, with all that said, AFM and DFM systems don’t come without pitfalls. Over time, some of the
Negative drawbacks to Active Fuel Management
So how does the system actually work? In the low load situations, the vehicles computer will send a signal to the engines Lifter Oil Manifold Assembly, which activates solenoids that open allowing oil to flow through special lifters housed within the ADM towers of the engine block. This oil then collapses the plunger inside the lifter, which won’t allow the lifter to engage the push rod, so the valves remain closed for that cylinder. Obviously, with the valves closes, no air can enter or exit that cylinder, meaning it provides no power. When engine load increases, the computer sends the signal back to the lifter oil manifold assembly to close the solenoids, oil bleeds off of the lifters and they return to natural operation and the cylinders begin contributing again.
With so many internal working mechanisms required to turn on and off thousands of times, it’s only natural that overtime these small pieces begin to wear and create problems down the road. It’s quite common for an AFM equipped engine to start seeing excessive oil consumption starting as early as 70-80,000 miles. There have been stories of as much as 2-quarts of oil burned in a basic 3000-mile oil change interval. This obviously affects engine efficiency, durability, maintenance costs, along with adding to other underlying issues like hesitation on acceleration, engine shudder, and a frustrating exhaust drone in the cab when running in low power modes.
Luckily for the GM owners everywhere, there is aftermarket support here that can help prevent some of these expensive repairs and failure modes. Range Technology of Ogden, UT developed a simple to install, end all cure all, for the troublesome Active and Dynamic Fuel Management systems. Their AFM/DFM Disabler module will simply plug direct into your vehicles OBD-II diagnostic port under the dash, automatically detecting the AFM/DFM system and disabling it for good. No programming required, no permanent changes to the vehicle, and best of all, no traces left on the PCM should you still be under a factory warranty. The AFM/DFM Disabler can be unplugged returning the vehicle to factory function in seconds and can be reinstalled just as easily once dealer warranty work is completed. One part number covers just about every applicable GM application from 2007-2020 and the module can be moved from one vehicle to another at any time.
Active Fuel Management (AFM), otherwise known as Cylinder Deactivation is a General Motors engine technology that shuts down half of the engine's cylinders in light driving conditions to improve fuel economy.
**The table below shows the engines that were originally equipped with AFM.**
The AFM system can be identified by its components.
Valley Cover - The AFM cover is called the Lifter Oil Manifold Assembly (LOMA). It's ribbed with solenoids on the underside. It also has an electrical connector on the back. (Non-AFM engines have a smooth cover.)
Engine Block - All Gen. 4 blocks have AFM towers and oil passages cast in. However, they are only functional on engines that used AFM.
Lifters - AFM engines use special lifters for cylinders 1, 4, 6, and 7. They are taller and have special oil holes.
**Engines with AFM also use a special camshaft, a high-volume oil pump, and a pressure relief valve in the oil pan.**
When engine load is low:
**Since no air can get in or out, 4 cylinders provide no power. The engine is running on only 4 cylinders.**
The AFM cylinders are opposite one another in the firing order. In 4 cylinder mode, they act like air springs. This allows for smooth operation.
When engine load increases:
**All 8 cylinders are now powering the engine.**