what is 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 more fuel-efficient under certain conditions.

So Why Turn it Off?

There are a few reasons:

  1. Many people find the four-cylinder sound annoying if their vehicle is equipped with a louder aftermarket exhaust.
  2. Some drivers want V8 power under their foot at all times.
  3. AFM lifters have a history of failing 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 install an AFM Disabler, and the second is to install an AFM Delete Kit. Here’s what you need to know:

1. Install an AFM Delete Kit

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:

  • You MUST upgrade to a non-AFM camshaft because the cam lobes in the four AFM cylinders are ground differently. The engine will have 25 less pounds of compression in those four cylinders which can result in a misfire code.
  • You will need to turn off the AFM system using a computer programmer or custom tuning.
  • It’s a little more work, but it’s recommended that you plug the pressure relief valve in the oil pan.
  • It is also recommended that you switch to a standard-volume oil pump.

2. Install an AFM Disabler

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. 

 

GM/Chevy Engines Factory-Equipped with AFM

Engine Displacement RPO Code
5.3L LY5 LC9 LH6 LMG LS4
6.0L L76 L77 LFA LZ1
6.2L L94 L99

Lifters

AFM engines use special lifters for cylinders 1, 4, 6, and 7. They are taller and have special oil holes.

LS - AFM lifters labeled

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

How Active Fuel Management (AFM) Works

(Image/GM Media)

When engine load is low:

  1. The computer sends a signal to the LOMA.
  2. The LOMA solenoids open.
  3. Oil flows to the special lifters through the AFM towers.
  4. The oil collapses the plunger inside the lifter.
  5. 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:

  1. The computer sends a signal to the LOMA.
  2. The LOMA solenoids close.
  3. Oil bleeds off the lifters.
  4. The lifters return to normal operation.

All eight cylinders are now powering the engine.