Inside the 5.7L HEMI® Multi-Displacement System

April 22, 2011 | by | 24 Comments

As part of our ongoing series getting inside the technology of our hardworking trucks, we once again chatted with engineer Mike Cairns about the significant R&D we put into the Ram Truck lineup. Now he’s back with a perfect example: a short video explanation of 5.7L HEMI® MDS technology. This highly advanced Fuel Saver Technology system seamlessly deactivates cylinders during regular cruising, but gives you all 390 horsepower and 400 lb.-ft torque when you put your foot down. Truly, it’s the best of both worlds.

 

  • T Blair

    I have recently bought a 1500 laramie and I just wanted to tell you guys what a great job you did.
    It is a masterpiece inside and out. The only thing I would change is the use of plastic for the grill and the wheel covers.

  • Ken Sniadowski

    Dear Michael Cairns,

    I would like to know why I am getting worse mileage with this new 2011 Ram 1500 with the new Hemi that I did with my 2005 Dodge Ram 1500 which I was able to get into it more and not able to do that or I watch my mpg go to nothing I have not averaged anything better then 12 mpg and that is calculated by the gas being replace and figuring out the MPG’s that way. Our truck payment increased somewhat which we figured with some of the savings in the cost on fuel but now my fuel cost has increased by about 30% as well so this is hitting us where it hurts. Also if I decide to manually shift to 2nd gear (up or down shift) it feels like it is inconsequential to say the least. The dealership said everything checks out but I was getting 16 to 17 MPGs driving around before with the same size truck the only minor difference is that it does not have the same gear ratio or slip differential. I need some help here as I am disabled with Chronic Back pain plus other issues and we are on a fixed income so I need to have this truck get at least what I was getting before so that it does not have such a drastic affect on our checkbook. We bought this truck because we were sold on the idea that with the new technology the MPG’s would increase but that is not the case whatsoever. Thank you in advance for your time cooperation in this matter.

  • John Duer

    I also have purchased a 2011 Ram 1500 Larmie with the MDS and totaly hate it. I went from a 2005 Ram 1500 and was getting 16 to 17 mpg and now i’m bearly getting 13, what up with that? I also have a serious lag in the foot feed when it trys to kick out from the MDS to the full 8 cylinders. I have been a dodge fan for many years and am considering traiding in my 2011 with 5500 miles on it to a new Ford. I have been to my dealer and talked to them about it and they look at me like I’m from outerspace. I feel that if I spend $45,000 on a truck I should be able to decide if I want to pay for the so called crappie fuel milage by having it turned off.

  • I JUST BOUGHT A 2012 RAM 1500 A LITTLE OVER TWO MONTHS AGO. HAD IT FOR A MONTH WAS MAKING A THUD SOUND WHEN I STOPPED AND WHEN I STARTED DEALERSHIP FOUND NOTHING, NOW ON JAN. 5TH 2012 MY ENGINE BLEW, ONLY HAS 4000 MILES. FIRST THEY FOUD A ROCKER ARM BROKE, THEN THEY FOUND PUSH RODS BENT AND SOMETHING WRONG WITH PISTONS, NOW THEY CALL AND TELL ME THEY HAVE TO PUT NEW HEADS ON MY TRUCK. SO I REQUESTED A NEW ENGINE, I PAID OVER $36,000 FOR THE TRUCK AND WITH THAT MUCH WRONG WITH MY NEW 2012 RAM TOUGH TRUCK I FEEL THE ENGINE SHOULD BE REPLACED. ITS BEEN TWO WEEKS IN THE SHOP WITH DEALERSHIP AND IVE BEEN LIED TO BY DODGE AND DEALERSHIP. WHAT SHOULD I DO?

  • brent

    why not put mds in you 2500 series trucks

  • Robert

    How can I cut the MDS off? I get worse gas mileage with it on around town than in V8 mode.

    • Redneck

      That’s bull, it doesn’t kick out of 8 till your over 50. If your over 50 in the city ya need to slow down. Then you’ll get better mpg! I get 15 city and 21 highway with my 07 Hemi. Also have tbs vararam under glass intake and my pipes are loud!

      • TapuOutn10 Forsure

        stop being stupid mine mds kicks in at 20 mph

  • derek

    can you disable and enable the mds system

    • Jesse

      Only with an aftermarket tuner

      • Bill Shields

        All you have to do is press the Tow/Haul button and it’s disabled.

  • Johnny boy

    My mds kicks in at 20mph

    • Jesse

      It’s a matter of RPM’s and rate of acceleration. Mine engages barely past idle at any speed. There are replacement non-MDS lifters but a tuner chip such as the Bully Dog GT that can disable it on the computer.

    • Bob

      MDS can ‘kick’ in as low as 8 mph. It is all based on engine load, not speed. At 3 mph it will kick off as the computer thinks you are either coming to a stop or you need to crawl, so to not load down the motor it goes back to 8 cylinder mode. There are several ways to disable MDS, but not sure why one would really want to, except for those who don’t simply understand the function of the system. It’s a great engine use on balance of power, mode, usability. Also the ECO light can come on during some circumstances where MDS is not engaged but unless you are really trying to make it happen you won’t even know it took place.

  • Dondi4

    When under 50 mph, my RAM 2014 seems to be missing and it seems like the engine is going to die, does any one have that problem?

    • Brian Taylor

      So does my ram 1500 trademan 5.7

  • Michael Alden

    Why would one want to dis able the M.D.S. ? It is a beautiful thing on a awesome motor. You get full power when your needs require it,and when you are cruising the motor runs along with no notice of difference of power. ONE thing…Should you have a loud exhaust,that 8 to 4 cylinder drop might irritate you,but might irritate you also when you fuel up. My 06 charger 5.7 will maintain 25 M.P.G. over the road. Power and great gas mileage for a hemi.

  • Michael Alden

    I understand you guys are talking trucks…Just saying.

  • Bob

    Do 2017 RAM Sport 4X4 trucks have MDS? Just bought a used one (ignition orange crew cab) and it does not have the ECO icon on the instrument panel at any time. Went thru booklet saw nothing on MDS listed. Just curious

    • Darlene Pierson Sherman

      If you have a Hemi, yes. You have to go into the U for settings , display and scroll down to fuel saver in cluster.

      • Bob

        Yep, you are correct. Thanks for info. It works just fine now. Appreciate your help. Cheers

        • dardars

          No problem! I traded my 2015 Ign. Orange for a 2018 Power Wagon and I also sell them. Enjoy!

      • Miguel

        Does the 2018 ram 1500 4×4 with the 5 inch display have the fuel saver option? I don’t see it on the cluster either.

  • Scott Thompson

    How do you even know the MDS is on or off while driving? I dont notice a difference