By on April 23, 2020

Despite the switch to low-sulfur fuel and ever more stringent emissions regulations around the world, compression ignition technology still gets a bad rap, tarnishing the remaining crop of diesel engine offerings despite their fuel economy advantages.

In the world of heavy duty pickups and large commercial vehicles, it’s a case of diesel or what else? Electric motors powered by battery banks the size of a refrigerator warehouse? Gotta use what works.

Diesel engine maker Cummins sees plenty of life left in the technology, and believes better is possible. If gasoline engines can shut down cylinders at will to conserve fuel, why not oil burners?

With that in mind, the company has teamed up with Tula Technologies, a major purveyor of engine management software, to bring cylinder deactivation to big, burly diesels. On Wednesday, both companies announced findings of their collaboration on diesel Dynamic Skip Fire (dDSF) — the diesel version of the technology General Motors adopted on its gasoline V8s under the name Dynamic Fuel Management.

With dDSF, Cummins says an X15 (6.7-liter) inline-six test engine returned significant reductions in CO2 and smog-generating NOX emissions when fitted in a semi-truck, in addition to better fuel economy.

Cummins

“We will continue to innovate the diesel engine system to make it lighter, more reliable, powerful and fuel-efficient, and we are encouraged by the progress demonstrated in this collaboration and what it could mean for future diesel technology,” said Lisa Farrell, Cummins’ director of advanced system integration, in a statement.

Cummins already markets the X15 as the thriftiest diesel in its weighty class, with the six-pot generating up to 500 horsepower and 1,850 lb-ft of torque. With Dynamic Skip Fire, the engine would fire only the number of cylinders needed for by-the-second load requirements. If adopted on diesels big and small, the advantages for cost-conscious fleet operators and makers of heavy duty pickups, both of whom are staring down the barrel of new emissions regulations, are obvious.

“Our partnership with Cummins has given us the opportunity to expand our DSF technology beyond its success in gasoline engines,” said R. Scott Bailey, president and CEO of Tula Technology. “Demonstrating the capability to improve fuel efficiency while also achieving very effective emissions control is extremely important for all diesel engine applications in the future.”

In a joint release, the two companies said “the collaboration will continue with exploring future system optimization and viability to control noise, vibration and harshness in commercial vehicle applications.”

[Image: Toa55/Shutterstock, Cummins]

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46 Comments on “Diesel’s Not Done Yet: Cummins Explores Cylinder Deactivation...”


  • avatar
    jack4x

    The “15” in X15 means 15 liter. This is not the B series 6.7L used in pickups.

    Still, cool technology if it can hold up over the million mile plus lifetime of a semi engine.

  • avatar
    bkojote

    ” If gasoline engines can shut down cylinders at will to conserve fuel, why not oil burners?”

    Because the GM and FCA products with MDS or whatever GM calls this this struggle to make it to 40k miles, and Cummins is already on shaky ground with the Titan.

    • 0 avatar
      Jon

      “Cummins is already on shaky ground with the Titan”

      That earthquake stopped a while ago and its magnitude was minor and remote. Pure speculation here, but the two collaborated because Nissan was willing to try anything to boost its Titan sales had very little to loose. Cummins only wanted data on its shiny new thingy and to test the market for a new small light duty diesel that will be (re)introduced as a reconfigured/redesigned/way-better engine on a different and more reputable platform (Ram?) in 5-7 years. Basically: I suspect that Nissan was used as a Beta-Test by Cummins.

      • 0 avatar
        blockmachining

        What happened was Nissan and Ram were working on the replacement for the first generation Titan. A signed contract was in hand for Nissan to use badge engineering and start selling Rams as Titans. Then along cane the bankruptcy and the contract was null and void. That’s why the first generation Titan was in production so long. All of a sudden, Nissan had to design a new truck. That’s also how Nissan pulled ram’s boss away from Chrysler and how we got a Cummins into a Titan. We were already in bed with Cummins and had a foot in the door! We were going to use this lost production at the Nissan factory in Canton Mississippi to build more commercial vehicles.

        • 0 avatar
          EquipmentJunkie

          Also, I believe that this V8 Cummins was one of two engines (1 V8 + 1 V6) co-developed with the Department of Energy that dates back to the early to mid-00’s but never found a home.

    • 0 avatar
      thelaine

      I did not know that the cylinder deactivation technology in FCA trucks was unreliable or reduced engine life. I was pretty excited about it. That is disappointing.

    • 0 avatar
      SSJeep

      Now that is funny.
      Of course MDS motors make it more than 40k miles. The Pentastar V6 is MDS equipped and is one of the most reliable engines on the market.

      As for the GM MDS problems, yes, there are some known issues with GM MDS 8 Cylinder engines causing premature cam roller wear and cam damage, but that doesnt show up until the 100-150k mile mark and can be avoided by adhering religiously to an oil change regimen. The same applies to the Hemi 8 cylinder.

      • 0 avatar
        ajla

        I don’t believe any version Pentastar V6 uses cylinder deactivation, not even the eTorque ones. It does have (defeatable) stop/start (called ESS) in certain applications but that’s a different thing.

        On my V8 Charger RT the engine made it past 45k fine with the MDS system but it did cause some slight NVH issues.

      • 0 avatar
        thelaine

        Glad to hear. The Hemi was the one I was interested in. Oil maintenance is a religious issue for me already, so no problems there.

      • 0 avatar
        Art Vandelay

        Anything that is more advanced than say, 1990 or so level tech will get a good amount of scorn here (And some seem to be convinced the Malaise era was the peak of the internal combustion engine). Yes, you can’t do 20,000 mile oil changes on this stuff. But anything that even resembles a maintenance schedule will keep these, turbos, and pretty much anything short of a modern diesel running well for a long time.

    • 0 avatar
      ajla

      If we are talking about unreliable cylinder deactivation systems then Honda deserves just as much scorn as GM and probably more the ChryslerCo.

  • avatar
    JimC2

    I’m curious how they shut down cylinders- is it just don’t put fuel into the cylinder for the one cycle or does it also involve selective valve closing (or something major like that). Where I’m going with this is pumping losses. Even in a diesel that’s technically wide open throttle all the time, it takes work to pump air through an unused cylinder.

    Since they state there are fuel economy and emissions improvements, I’m all for further R&D. I’m just curious how they’ve implemented this, that’s all.

    • 0 avatar
      millerluke

      A short video here https://youtu.be/W4JDi0K8htY shows how Chrysler’s system works. It uses a combination of fuel cut-off, spark cut-off and valve closing.

      • 0 avatar
        JimC2

        I understand the different ways that it works in gasoline engines (engines that are on the market, not engines that are in the lab or on drawing boards). I meant what Cummins is doing with this particular diesel engine.

        • 0 avatar
          JimZ

          er, why would it be any different? Keep the valves closed so you’re not wasting energy on pumping losses, then just don’t inject fuel into deactivated cylinders.

          probably no more complicated (if not even less complicated) than a Jake Brake.

          • 0 avatar
            JimC2

            Yep, but again, I’m just curious how the little moving parts work. Usually when there’s a story about a new engine featuring cylinder deactivation, the engine maker likes to showcase their work with a little tech writeup. And plenty of fans out there like learning a few of the details, even if it makes no difference at the end of the day whether it’s an extra mechanical pin in each rocker arm or some other clever widget making the magic happen.

  • avatar
    SCE to AUX

    “staring down the barrel of new emissions regulations”

    Would there need to be a rewrite of the test protocols to see the advantage of this technology?

    • 0 avatar
      JimZ

      medium and heavy duty engines are rated at the engine level (emissions limits in g/hp-hr) not at the vehicle level. would all depend on what the test cycles look like.

  • avatar
    cprescott

    Take a reliable multi-hundred thousand mile engine and add cracks in its armour.

    Sounds like a great idea (sarcasm).

  • avatar
    Matt51

    Diesel is dead. Electric won’t kill gasoline cars, but will replace long haul trucking diesel. Continued improvement in mileage for gasoline cars means no need for dirty diesel. RIP Cummins.

    • 0 avatar
      Bill Wade

      I wonder how long it would take to recharge the massive battery pack required in an OTR truck?

    • 0 avatar
      ajla

      “RIP Cummins.”

      You are aware there are diesel applications beyond highway vehicles?
      Are we also going to get full electric locomotives, agricultural pumps, and backup generators? Maybe some day, but those seem like a long way off.

      • 0 avatar
        schmitt trigger

        And agricultural and construction machinery…….

        Wait a minute? Did I forget about ships?
        And I know, I know: Gas turbine technology is finding its way in more and more ships. But it is not mainstream yet, and for the really gigantic engines (I am talking Wärtsilä sized engines) they will be difficult to completely replace.

    • 0 avatar
      Imagefont

      Yes, those Tesla Electric Semi long haul trucks are taking over!
      Oh wait….

      • 0 avatar
        indi500fan

        Yeah those Tesla trucks are amazing. That fleet delivering the batteries and motors from Nevada to Fremont actually has more charge in the pack when they arrive because it’s downhill all the way.
        At least that’s what the Tesla fans claim.

    • 0 avatar
      HotPotato

      I’m thinking long-haul trucking will be the last to electrify. High speed, high weight, long distance — not the wheelhouse for electric power, due to the poor energy density of batteries.

      Battery power is a natural for medium-duty trucks though, since they tend to drive short routes with lots of stop and go — beverage delivery trucks, school buses, Brinks trucks, local UPS and FedEx trucks — just not interstate trucks. This could also be a big benefit for urban air quality, since lumbering two-axle box trucks tend to be the worst polluters I see on the road.

      • 0 avatar
        dal20402

        HotPotato, I agree. Diesel engine makers are in for a world of hurt, but the reason isn’t the long-haul trucking application, it’s all the day-use truck and bus applications.

        • 0 avatar
          indi500fan

          Indy bought a fleet of electric buses last year and the range problems in cold weather were enough to have them switch to diesels for a follow-on order.

      • 0 avatar
        EquipmentJunkie

        From what I hear, Nikola will have some interesting future options.

        Diesel won’t be dead anytime soon. Its demise will be measured in decades.

      • 0 avatar
        indi500fan

        Just read a write-up on the new Volvo VNR truck.
        It’s 8,000 pounds more than the diesel version, and that comes right out of the payload.

    • 0 avatar
      Lou_BC

      @Matt51 – battery technology isn’t near efficient enough to replace diesel engines in any commercial long haul application. I watched an interesting video where a fellow did the math for replacing diesel engines with battery electric motors in ocean going freighters. He applied the math to “Suez” sized vessels. 1/2 of the cargo capacity of the boat would be lost to battery packs. IIRC that was based on bunker fuel costs (pre-oil collapse).

      • 0 avatar
        ToolGuy

        Thanks Lou, I was just about to mention container ships. There is a spectrum of applications where electrification will and won’t make sense.

        If anyone has any interest in modern maritime shipping, this museum is worth a visit:
        http://www.gulfquest.org/

        [You can teach your kids to say RoRo.]

    • 0 avatar
      JimZ

      yeah, those electric semis which have range matching a diesel tractor with twin 150-160 gallon fuel tanks.

  • avatar
    bullnuke

    I have utilized cylinder deactivation on diesel engines in the past. I operated a pair 1600hp Fairbanks-Morse engines (10-cyl, 20 piston opposed) and there were certain times where it was necessary to disconnect a cylinder or two from the fuel rack with the engine running. The engines didn’t really seem to care much – kept running at 720rpm. This was fairly routine in submarines with GM V or F-M engines when a cylinder failure occurred and the engines were needed to run.

  • avatar
    ThomasSchiffer

    I will continue to drive Diesels as long as they are available. For my driving needs and style there’s nothing else that comes close to providing fuel economy combined with spirited fast driving on the Autobahn. No gasoline engine (much less an EV) can offer those long legs while sipping so little fuel.

    And this article is a bit misleading. Diesels are still very much popular in Europe, they’re considered even cleaner than gasoline engines (the modern EURO6 Diesels). Several studies have shown that the air which comes out of the tailpipe of a modern Diesel car is cleaner than what is sucked in at the front.

    • 0 avatar
      Imagefont

      Diesels that clean the air! Well there you go, our environmental problems are solved!

    • 0 avatar
      Art Vandelay

      “Several studies have shown that the air which comes out of the tailpipe of a modern Diesel car is cleaner than what is sucked in at the front.”

      I am going to guess that Volkswagen was involved in those studies in some way or another. Do you know of any of them though? I’d be lying if I said I wasn’t interested in perusing them.

      • 0 avatar
        ThomasSchiffer

        Here is the information. It’s difficult to find links on this in English, most are in German.

        https://www.globalfleet.com/en/safety-environment/europe/features/newest-diesel-engines-clean-air

        The newest Volkswagen Diesel engines also pass the current emissions requirements. There is still so much potential here and for drivers like myself who need the fuel economy but also enjoy speeding the Diesel engine is perfect.

      • 0 avatar
        ThomasSchiffer

        Also, they do no ‘clean the air’ in a physical sense. The exhaust is simply ‘cleaner’ than what is sucked in at the front. It’s an indication of how clean modern EURO6d Diesels are.

        • 0 avatar
          DenverMike

          It sounds like you should plumb your diesel exhaust right into your car’s HVAC. Bypass its worthless filter too! (lol?)

          I’ve heard that too, and I believe it’s true, but the air would have to be very polluted to begin with. Or Paris or London.

          All that is very impressive and great for the environment too. But it’s asking the diesel to perform a lot of unnatural things, unrelated to moving you down the road.

          Something’s gotta give, and I’m sure it won’t be cheap!

        • 0 avatar
          dal20402

          I’ll believe the Euro6 (and Euro5 for that matter) diesels are performing as claimed when I see an independent, non-industry-funded academic study showing it.

          It is now clear that essentially all of the first generation of Euro5 engines, from nearly all makers, were fraudulent, and emitted many times the pollution in real-world service that the OEMs claimed. And we’re just expected to take it on faith that the OEMs have cleaned up their act.

          You can test this for yourself: just ride a bicycle immediately behind a “modern” diesel that is starting from a stop. You will not be convinced that the exhaust is cleaner than ambient air, that’s for sure.

          • 0 avatar
            JimZ

            well, it depends on your frame of reference- is the “Air” coming out of the tailpipe perfectly clean? or is the air going into the engine just filthy to start with?

          • 0 avatar
            DenverMike

            Try inhaling a lung-full of Euro6 exhaust directly at the tailpipe end. I did and it’s still complete death compared to normal air.

            I don’t have a death wish, but just take my word for it. No, I was strapping down a diesel BMW after loading in on to a 4 ft high flatbed. I forgot the engine was still running and inhaled just as I got to the back of the right rear tire.

            Talk about gag. I’m sure it took minutes or hours off my lifespan.

  • avatar
    DieselTechForum

    why is it that the author or page editors choose such a ridiculous and non representative image of a smoking pick up truck for this story that is about efficiency and improving emissions?

    One must wonder if it is a bias against diesel, that smokey trucks get more clicks than others or just laziness.

    Come on TTAC- get real with your images– it cuts way down on any journalistic integrity when there is such a poor choice of images to go with a story. How about some ‘splainin on how and why that image was chosen?

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