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-   MDS (http://www.ramforumz.com/forumdisplay.php?f=147)
-   -   Explain how MDS operates. (http://www.ramforumz.com/showthread.php?t=56302)

DBryant 06-29-2010 02:47 PM

Explain how MDS operates.
 
I know this has probably been asked before, could not find it with search. How does the MDS system work? Used to be a drag racer in the 60's so I know engines, just don't know how MDS works.

City Slicker 06-29-2010 03:05 PM

http://www.ramforumz.com/showthread.php?t=47443

erm 06-29-2010 03:07 PM

From Remerson228, our resident tech:

The Multiple Displacement System (MDS) provides cylinder deactivation during steady speed, low acceleration and shallow grade climbing conditions to increase fuel economy. Both four and eight cylinder configurations have even firing intervals providesmooth operation. Two cylinders on each bank are active when the engine is in four-cylinder mode – every other cylinder in the firing order. All of the cylinders that are deactivated have unique hydraulic valve lifters that collapse when deactivated to prevent the valves from opening. Engine oil pressure is used to activate and deactivate the valves. It is delivered through special oil passages drilled into the cylinder block. Solenoid valves control the flow. When activated, pressurized oil pushes a latching pin on each valve lifter, which then becomes a “lost motion” link. Its base follows the camshaft, but its top remains stationary, held in place against the pushrod by light spring pressure but unable to move because of the much higher force of the valve spring.

NOTE: It is critical to use the recommended oil viscosity in 5.7L engines that use MDS.

Deactivation occurs during the compression stroke of each cylinder, after air and fuel enter the cylinder. Ignition then occurs, but the combustion products remain trapped in the cylinder under high pressure, because the valves no longer open. No air enters or leaves. During subsequent piston strokes, this high-pressure gas is repeatedly compressed and expanded like an air spring, but fuel is not injected.

RootBeer 06-29-2010 04:09 PM

Is there a way to tell if the MDS is working?

RamTech 06-29-2010 05:10 PM

The sound of the engine is a big giveaway.

RootBeer 06-29-2010 05:27 PM

Quote:

Originally Posted by Remerson228 (Post 249423)
The sound of the engine is a big giveaway.

Sound? What sound? This truck is so quiet the only time I hear it when I put my foot in it. :LOL:

CdnoilRAM 06-29-2010 06:56 PM

I prefer the answer: Magic :LOL

Randy has the real info on it, and like it says there, the viscosity is VERY important, so use the oil type that your cap says or you can run into issues, especially if you live in colder regions.

RamTech 06-29-2010 07:32 PM

Quote:

Originally Posted by brianwl (Post 249437)
Sound? What sound? This truck is so quiet the only time I hear it when I put my foot in it. :LOL:

My point exactly! When you hear that sound, you can rest assured you are NOT in MDS mode!

RoninHemi 07-11-2010 08:24 PM

MDS on?
 
Quote:

Originally Posted by brianwl (Post 249392)
Is there a way to tell if the MDS is working?

I found that if you have an '10, the message center in the dash can be set to let you know when you are in economy mode. There is a sound and some feeling change.

RamTech 07-11-2010 08:49 PM

Quote:

Originally Posted by RoninHemi (Post 258256)
I found that if you have an '10, the message center in the dash can be set to let you know when you are in economy mode. There is a sound and some feeling change.

Eco mode is NOT an indication of MDS engagement.


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