Multi-Displacement System (Cylinder Deactivation) Question

[dwsiddall]

I bought a pre-owned 2016 Ram 1500 LoneStar Edition and it is supposed to have the Multi-Displacement System and shut down cylinders at highway speeds to save on fuel.

My question is, how do I know when it kicks in? Should there be an indicator of some sort? How do I know it's working?

Thanks....

 

[jws123]

When your at crusing speed/not under load you will hear/feel it kick in listen to exhaust tone some people dont notice it as much. It depends on the condition of the system like my 2011 will make it impossible to drive normally shakes whole truck alot of us turn it off due to it being a pain in the ass and saving little to no gas.

 

[Jeepwalker]

Mine, the word 'Eco' comes on the driver information center (DIC). Then it disappears when it's not in the MDS mode ..for example during acceleration or passing, etc. Mine's pretty seamless, sometimes you can't hardly feel when it's engaged or disengaging. Sometimes there is a stutter when (before) it wants to come out f that mode.

Note: By manually shifting the tranny into a lower gear (keeps the trans from going into a higher gear than I shift into), it keeps the tk from going into the Eco mode.

 

[DILLIGAF]

ECO mode and MDS are 2 different things.

You can turn off that stupid ECo light in the options as well

Youll feel it. truck feels like hot garbage when it kicks in.

 

[tron67j]

There is a lot written in this subject, you should search and read through those threads. Consensus appears to be that eco light and mds being on are not always related, MDS cannot be deactivated through code changes but turning on tow mode prevents it from engaging, and it sounds like crap on many muffler systems.

 

[ThunderMug95]

If you have a performance exhaust you will REALLY notice it. Sounds like a wildebeest with a stutter. When it kicks out of “Liar Mode”errr I mean MDS mode its like a muted hiccup.

 

[Travelin Ram]

I‘ve had two 6.4’s and in these the Eco light is consistent with 4 cylinder operation. If you are observing the instantaneous MPG mine will jump from high teens (8 cyl) to low twenties (4cyl) cruising at a steady state ~50 mph.

My 2019 the change in sound and NVH was barely perceptible. In the 2022 I do notice it a bit more, probably because in this year RAM deleted the frame mounted vibration dampers below the cab. However it’s not at all objectionable to me, personally. I’ll take that 4-5 mpg when I can get it.

 

[DILLIGAF]

MDS sucks, Tune it out

 

[Rlaf75]

Do yourself a favor and don't get your hopes up too high. The MDS system isn't going to miraculously make your mpg jump from the normal 13 up to 19 mpg. I personally think it's over rated.

Now to answer your question, there will be a green "eco" indicator on the dash that lights up when the mds is active. It's very sensitive to the throttle and turns off the second you accelerate. There may also be a slight different feel to the truck or a drone when it's active. If you're paying attention, you'll feel the system shut of with the slightest push of the gas pedal. It almost feels like it shifted gears. To make sure it's working, get on a flat stretch of highway and cruise about 65 mph with very light pressure on the gas pedal. The eco light should come on. Keep it there for a bit then gently accelerate and you should hear and feel a difference. Again it very sensitive

 

[mikeru]

Since this is a 4th gen forum, I'll describe how this works on a 4th gen (1500). MDS and the Eco mode light are two different things. There is no indicator light to tell you when MDS is active. MDS will activate after certain conditions are met. If you have the Eco mode light enabled, it simply means you are driving in an economical way when it lights up. The Eco light often lights up when MDS is active, simply because the conditions for both are similar. But MDS can activate without the Eco light turning on. Some people report they can't tell when MDS is on, and some say they really feel it even with stock exhaust. As suggested above, it will become more pronounced if you upgrade your exhaust to something more aggressive sounding.

 

[Maryland_Man]

With a 5.7L, found best mpg is on highway, speed 60-65, adaptive cruise control active. With light traffic and not many truck controlled accelerations from terrain changes, got about 22-23 MPG. Driving around town with many lights 13-15 MPG. Doing the math, I'm a poster boy for EPA rating on window sticker @ 17 MPG average.

On highway with ACC active, ECO light will be visible and rumble from MDS not noticeable. Would believe truck computer is better than I am at engaging acceleration to maintain speed. Good idea to disengage either cruise control mode when encountering substantial curves with elevation changes on highway. Usually designated by highway warning signs. The truck will attempt to accelerate to climb into a curve to maintain speed. Overall, it's a step forward in bringing increased automation to the driving experience, but need to consider certain driving scenarios.

In addition, BSM reliability is lower when on a tight turn.

 

[RodRamCar]

With a 5.7L, found best mpg is on highway, speed 60-65, adaptive cruise control active. With light traffic and not many truck controlled accelerations from terrain changes, got about 22-23 MPG. Driving around town with many lights 13-15 MPG. Doing the math, I'm a poster boy for EPA rating on window sticker @ 17 MPG average.

On highway with ACC active, ECO light will be visible and rumble from MDS not noticeable. Would believe truck computer is better than I am at engaging acceleration to maintain speed. Good idea to disengage either cruise control mode when encountering substantial curves with elevation changes on highway. Usually designated by highway warning signs. The truck will attempt to accelerate to climb into a curve to maintain speed. Overall, it's a step forward in bringing increased automation to the driving experience, but need to consider certain driving scenarios.

In addition, BSM reliability is lower when on a tight turn.

4th Gens don't have adaptive cruise control (sometimes I wish they did). I average 13mpg with mostly city but a decent amount of highways too and I am not into the accelerator. I drive conservatively most days. Ram has never been accurate with their mpg ratings but idc about mpg.

 

[RodRamCar]

according to what I have been told by the more Ram-educated minds on here, de-activating MDS through a tune will mean less lubrication on cam/lifters. Apparently it's better when in MDS and still at the end of the day, i'd rather have MDS activation removed through a flash tune but I would also raise idle RPM to 700 or 750 too. I don't know why that is and maybe @DILLIGAF @Burla @HEMIMANN or any of the other guys who are deep into the oil threads can shed light.

 

[joesstripclub]

according to what I have been told by the more Ram-educated minds on here, de-activating MDS through a tune will mean less lubrication on cam/lifters. Apparently it's better when in MDS and still at the end of the day, i'd rather have MDS activation removed through a flash tune but I would also raise idle RPM to 700 or 750 too. I don't know why that is and maybe @DILLIGAF @Burla @HEMIMANN or any of the other guys who are deep into the oil threads can shed light.

From what I understand, when MDS is activated it sends additional oil to lubricate the lifters.

 

[joesstripclub]

There is a lot written in this subject, you should search and read through those threads. Consensus appears to be that eco light and mds being on are not always related, MDS cannot be deactivated through code changes but turning on tow mode prevents it from engaging, and it sounds like crap on many muffler systems.

This is incorrect, MDS can still engage when in tow mode. The only way to shut it off is to manually shift the truck into 8th gear if you have an 8 speed.

 

[miles01]

The MDS is b#*•• S*^#%* it is only to satisfy the EPA fuel milage for factory fleet average mpg that is required for all vehicle manufacturers.
I owned a 1500 with 5.7 and now a 2500 with 6.4.
All the MDS is activated 4 cylinders when there is a tailwind on level ground or under 90 kmh (55mph) on level ground or going downhill.
Overall maybe 1/3 to 1 mpg better mileage on a full tank of gas used that brings the overall fleet for the manufacturer up and we pay for the useless to us technology.

 

[indept]

Mine, the word 'Eco' comes on the driver information center (DIC). Then it disappears when it's not in the MDS mode ..for example during acceleration or passing, etc. Mine's pretty seamless, sometimes you can't hardly feel when it's engaged or disengaging. Sometimes there is a stutter when (before) it wants to come out f that mode.

Note: By manually shifting the tranny into a lower gear (keeps the trans from going into a higher gear than I shift into), it keeps the tk from going into the Eco mode.

The eco light isn't 100% tied to MDS. The eco light can come on with light throttle but no mds as tron67j mentioned in post 5. Listen for the change in exhaust tone and you will hear MDS turn on & off.

 

[Daniel Ortiz]

I bought a pre-owned 2016 Ram 1500 LoneStar Edition and it is supposed to have the Multi-Displacement System and shut down cylinders at highway speeds to save on fuel.

My question is, how do I know when it kicks in? Should there be an indicator of some sort? How do I know it's working?

Thanks....

@dwsiddall , from what I understand and as others have said, the "ECO" indicator on your instrument panel must be on for MDS to engage, however I don't think MDS necessarily has to be engaged if the "ECO" light is on. I'm not really sure, as my truck is nigh seamless in the transition in both sound and feel.

As others have said, I've heard Tow/Haul mode prevents MDS from engaging, however it also changes the shift points of your transmission. It assumes you are pulling a big heavy mass and so lets the engine rev higher before shifting. Another way to prevent MDS from engaging is to activate the gear limiter (the "Gear -, Geat +") buttons on your steering wheel, and setting it to '8.' That allows all 8 gears to be used by the transmission, but also prevents MDS from engaging, and keeps your shift points the same. Using this method, I can tell it's not activating MDS because the truck is more responsive when I accelerate from a steady speed. It generally feels like it drives better this way.

The downside of keeping MDS off all the time is that the lifters receive only their standard oil pressure. When MDS is activated, the lifters receive higher than standard oil pressure to activate them. Generally, HEMI owners try to do everything we can to keep our lifters as well-lubricated as possible, due to the dreaded HEMI tick (the bad one).

The good side to keeping MDS off is that on each cycle the MDS cylinder intake valves receive their steady supply of gasoline/air mixture to keep the intake parts all nice and clean. Activating MDS means they no longer get that nice constant cleaning effect from the gasoline, but still have to contend with PCV vapor hanging about. Also, without the high pressure of burning fuel, some say there is a greater tendency of oil to make its way past the piston rings and into the combustion chamber. That probably only happens if your PCV system is in poor condition, but who knows.

I tend to disable MDS on long trips, and let it operate normally on short trips.

 

[CanuckRam1313]

This is incorrect, MDS can still engage when in tow mode. The only way to shut it off is to manually shift the truck into 8th gear if you have an 8 speed.

Exactly! I press the -gear button and the number 1 comes on my dash. I then +gear it to number 8. MDS is off and no damn way I ever want it on. It saves pretty much zero fuel. And as far as I'm concerned it is a detriment to the the overall enjoyment of the vehicle. That annoying lag when it's on and you go to accelerate is unbearable. The almost shuddering / lagging feeling when it's on and it trying to decide how it should shift and manage the engine is ridiculous in my opinion. 8 cylinders all the time is a happy HEMI (for me, anyways).

 

[ramffml]

From what I understand, when MDS is activated it sends additional oil to lubricate the lifters.

You don't need MDS for proper lubrication. If you did, those who tow would destroy their engines very quickly as MDS is never active while towing. In 5th gens T/H disables MDS (not sure on 4th) but in any case, the load on the engine is so high while towing my trailer that it doesn't get out of 7th gear and will often sit in 6th at 2300 RPMs. There is just no way MDS can kick in under those conditions, regardless of whether it's turned off electronically with T/H.

I have 75,000 KM on my OD, all of them put on without MDS turning on unless I happened to forget to disable it.