WHAT IS AFM/DOD AND WHY DELETE IT
Active Fuel Management (AFM) is a trademarked General Motors technology that improves gas mileage by shutting down half of the cylinders under light-load conditions to reduce fuel consumption. It is also known as Displacement on Demand (DoD) or cylinder deactivation.
HOW DOES AFM AFFECT PERFORMANCE?
AFM is good for gas mileage and can be 5-7 percent (claimed) more fuel-efficient under certain conditions.
WHY TURN IT OFF?
There are a few reasons:
Many people find the four-cylinder sound annoying, especially if their vehicle is equipped with a louder aftermarket exhaust.
Some drivers want V8 power under their foot at all times.
DOD lifters have a well documented history of failure and oil consumption can be a problem.
HOW TO DELETE OR DISABLE AFM ON GM/CHEVY ENGINES
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 disable DOD/AFM via a tune and the second is to install an AFM Delete Kit. Here’s what you need to know:
1. INSTALL A DOD/AFM DELETE KIT
A DOD/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:
You MUST upgrade to a non-AFM camshaft because the cam lobes in the four AFM cylinders are ground differently. The engine will have less compression in those four cylinders which can result in a misfire code and poor performance.
You will need to turn off the AFM system via custom tuning.
It’s a little more work, but it’s recommended that you plug the pressure relief valve in the oil pan.
2. DISABLE AFM/DOD VIA TUNE
An AFM/DOD tune 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: An AFM/DOD delete tune should only be used if the valvetrain is in good working order or if an AFM/DOD delete kit has been installed.
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. It is recommended to switch to a standard volume oil pump during the swap.
NOTE: Once you install a DOD/AFM delete kit you must tune the vehicle. Not doing so will cause the vehicle to attempt to revert to 4 cylinder mode.
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.
HOW ACTIVE FUEL MANAGEMENT (AFM) WORKS
When engine load is low:
The computer sends a signal to the LOMA.
The LOMA solenoids open.
Oil flows to the special lifters through the AFM towers.
The oil collapses the plunger inside the lifter.
The collapsed lifters will not engage the pushrods and both valves remain closed.
Since no air can get in or out, four cylinders provide no power. The engine is running on only four cylinders.
The AFM cylinders are opposite of one another in the firing order. In four-cylinder mode, they act like air springs and allow for smooth operation.
As engine load increases:
The computer sends a signal to the LOMA.
The LOMA solenoids close.
Oil bleeds off the lifters.
The lifters return to normal operation.
All eight cylinders are now powering the engine.
Want to disable AFM/DOD? Contact us today!
TUNING AND GAS MILEAGE FOR YOUR LS CAR OR TRUCK
Why does tuning help with gas mileage? Is it worth it? It is.
Why does tuning help with gas mileage? Is it worth it? It is.
Here is EKY Tuning's explanation on why: Most trucks have a 26 gallon tank, if a truck gets 15 mpg (which is pretty average) that's 390 miles per tank. An increase to 18 mpg gives you a 20% increase and 468 miles per tank.
After the purchase of 5 tanks you're basically getting a free tank of gas because every tank now runs you 78 miles more. At $85 per tank, that's a great savings. Also an easy target increase with a tune from EKY Tuning!
If you want to look at it in terms of the tune paying for itself, in 14 tanks of gas it has paid for itself completely. At $249.99. (Which is the cost of a tune and shipping here at ekytuning.net.) Fourteen tanks may seem like a lot but that’s maybe 2-3 months worth or even less, depending on driving habits. Ultimately a custom tune does help with gas mileage. Not only does tuning give you money back in your pocket, but “free” gas too!
Interested in getting a tune and better mileage? EKY Tuning can get you lined out!