DoD adjustment....not disable/enable...

[Anders_Y]

This one's for Mike and Lew,

First, please reply with a link if this has already been discussed, I didn't find this exact topic within 10 minutes of searching and could be wrongly posting.

I'm wondering if there's any way to change the threshold in which the DoD kicks in. Maybe have it kick in a little earlier or later (or I guess at less or more commanded throttle). I've been trying to research and learn how the computer actually makes this decision. Can't seem to find documentation that tells which sensor readings the computer uses to do it. Anyone have an answer or idea on this?

Thanks guys!!!!

-Anders

P.S.- Haven't been in the forum for awhile but just read about the tcm...can't frickin' wait!

[mikel]

This can be done with some custom tuning.

FWIW, the range is about as opened up as it can be in the MPG booster tunes.

[06MonteSS]

yeah, what mike said ^ ^

there are settings if you were to get a custom tune done, to change the rpms at which dod is allowed to activate... but other than that, the throttle position settings are already changed which allow it to stay in dod mode longer...

DOD operation depends on a lot of things... rpms, throttle position, vacuum pressures, oil pressures, etc etc...

I've got documentation from GM that will give you insight as to how it all works, and also the reasons/issues that will not allow it to work.... they're attached below...


================================

Displacement on Demand (DoD) General Information

The original name was Displacement on Demand (DoD). For the start of the 2006 model year GM renamed it Active Fuel Management (AFM).

During light load conditions while in 3rd or 4th gear the ECM will shut down cylinders 1, 4, 6, and 7 to put the engine in V4 mode. The engine will not enter V4 mode while cranking, idleing, or heavy acceleration. To shut down the cylinders the intake and exhaust valves stay closed and the fuel injectors stop feeding gas. The ECM times the shutdown so that each deactivated cylinder keeps the exhaust charge from the previous combustion cycle. This pressure on the pistons keeps them from rocking around in the cylinder causing vibration and oil consumption. Complete cylinder deactivation is accomplished in about 250 milliseconds.

The engine components involved in cylinder deactivation are the valve lifter oil manifold (VLOM) and special valve lifters. The VLOM consists of 4 solenoids that control oil flow to 8 valve lifters. Each solenoid goes with a certain cylinder and its 2 valve lifters.

When DoD is commanded on by the ECM the 4 solenoids energize and allow oil to flow to the valve lifters. The special valve lifters are made of an inner lifter and outer lifter with a spring loaded locking pin holding them together. When the oil gets to the lifters the pin is pushed out of place and the inner and outer part of the lifter are allowed to move seperately. The camshaft is still pushing on the outer part of the lifter, but the inner part of the lifter is no longer pushing up on the pushrod. This keeps the intake and exhaust valve shut permanently until the ECM commands DoD off. At this point the solenoids stop oil flow to the lifters and the spring loaded lifter pins lock back into place, causing the lifters to return to normal operation.

[Anders_Y]

Pure awesomenes! Thanks guys!

[dguth66]

Excellent info guys....Lew you have the goods man

[06MonteSS]

thx man