By on January 7, 2015

GM Ventures Sees Potential in Fuel Saving Technology

General Motors has played with cylinder deactivation technology since the days of Carter, sometimes successful, sometimes with more disastrous results.

With Tula Technology’s Dynamic Skip Fire, GM is banking on the former.

The technology — a result of the automaker’s 2012 equity investment in the startup via GM Ventures — uses “advanced digital signal processing with sophisticated powertrain controls to create a software-based approach to variable displacement engines.” This allows for a dynamic approach for cylinder management, with individual cylinders to be activated or deactivated on a case-by-case basis while maintaining proper torque at all speeds/loads and avoiding vibration issues.

GM believes employment of DSF could improve fuel economy among its various models by as much as 15 percent compared to other cylinder-deactivation methods, such as its Active Fuel Management system used by the likes of the Chevrolet Silverado and GMC Sierra, among others.

As for when DSF might appear, Tula CEO R. Scott Bailey couldn’t say much about the timeline, but that his investor views the technology as “production worthy,” per an interview with Autoblog. Other investors in Tula include Sequoia Capital, Sigma Partners and Khosla Ventures.

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31 Comments on “GM Banking On Dynamic Cylinder Deactivation For Improved Fuel Economy...”


  • avatar
    rpol35

    In an attempt to come up with a more consumer friendly sounding marketing name as opposed to Dynamic Skip Fire or DSF, GM is conducting a “naming contest”. So far, the number one choice has been V8-6-4; oh, um, ooops; never mind.

    • 0 avatar
      Lie2me

      After the Cadillac V8-6-4 debacle I wouldn’t go near this with a ten foot pole. Perhaps GM could concentrate their efforts on slapping together a diesel engine out of an existing V8, yeah that’s the ticket

      • 0 avatar
        BigOldChryslers

        Contrary to popular belief, the Olds 350 diesel was NOT a converted gas engine. It was designed with some critical dimensions the same as a 350 gasser so they could machine the blocks on the same equipment.

        • 0 avatar
          Lie2me

          You’re right and this was GM’s official statement on the engine:

          “All of the major parts, blocks, crankshaft, rods pistons and lifters have been strengthen to handle the higher compression ratios”

          … and we all know how well *that* turned out

          • 0 avatar
            rmmartel

            Would have turned out better if the mechanics working on them were properly trained and/or realized that working on a diesel engine is different from working on a gasoline engine.

            Things like reusing “torque to yield” bolts is a bad idea or using drygas to try to rid the fuel system of water and thereby damaging the injection pump.

            Of course this doesn’t excuse GM for *not* equipping the cars with water separators in the fuel system

        • 0 avatar
          Carlson Fan

          The biggest problem with the Olds diesels was that people drove & maintained them them like a gas engine. No doubt the design was less than robust but you could get 300K out of one if you knew how to drive and maintain it. I worked at a service station/towing company years back and most of them that came in were due to failed injector pumps. One of the mechanics that worked on them even owned one.

  • avatar
    dwford

    My GMC Sierra seamlessly toggles between V4 (yes, that’s what they call it) and V8 mode. If only the transmission could shift through the gears as smoothly.

    • 0 avatar
      BigOldChryslers

      I had a Yukon rental for almost a month last year. I kept the digital display on the mode showing the V8/V4 mode. I agree the transition between them was very smooth. Hated their 6-speed transmission though.

      • 0 avatar
        Carlson Fan

        The transition is absolutely seamless on our ’07 Tahoe. The two problems are: A – The oil consumption issues that start showing up on the 4 cylinders that shut down due to the rings gumming up. B – The fact that the 5.3 just doesn’t have the torque to keep the vehicle moving down the road without constantly having to switch into V8 mode. When driving city highways with heavy traffic sometimes it will hold the V4 mode for quite awhile due to the lake of wind resistance and the mileage is great, mid 20’s. But in rural areas where your pushing the air out out of the way it just doesn’t run in V4 nearly enough to make a difference. I’m convinced, at least with my truck, that the AFM was more of an EPA gaming tool than anything. It just doesn’t work in the real world. In fact the reason the Hybrid Tahoe has the 6.0 in it is because that allowed it to run in V4 mode longer than the 5.3.

  • avatar
    SCE to AUX

    Some people date others using this method.

  • avatar

    If GM combined Skip Fire with their old Cross-Fire fuel injection, would they call it a Miss-Fire?

  • avatar
    Fred

    I remember going to flea markets and guys hawking dead spark plugs to turn your 8 cyl into 6. Still today I just have an uneasy feeling about this technology, no matter how many computers you throw at it.

  • avatar
    thegamper

    I think the idea has a lot of potential, love to see it succeed. As for the name, I propose: “Duck Duck Goose Ignition Control”

  • avatar
    heavy handle

    The difference between this cylinder deactivation tech and current tech is that it deactivates individual cylinders in a near-random pattern. This keeps temps even, since a single cylinder will only skip every fourth firing (for example).

    The same principle is used to keep F1 cars idling on the start line without overheating (no radiator fans), so it’s probably not patentable.

    • 0 avatar
      APaGttH

      The other benefit I see is the deactivation is software controlled. ON the G8 the AFM lifters are a point of weakness on early production 09 models (bad lifters from Eaton) and a number of owners are doing full on DoD delete swapping out lifters and cams as the final solution to the problem.

      • 0 avatar
        JimC2

        There is another big benefit to using software control to deactivate one or more cylinders randomly- or not so randomly. They can update the software if there are wear patterns found once many of these engines are in service.

    • 0 avatar
      wmba

      Exactly, heavy handle.

      The first comments above crabbing about a 30 year old technology not working typify the blinkered attitude of so many here who take time out of their busy day to post irrelevant tripe. Hello, it’s 2015. Keep up.

      https://www.thetruthaboutcars.com/2014/07/schaeffler-run-on-two-cylinders-instead-of-three/

      Schaeffler Germany invented both the GM and Chrysler pushrod V8 cylinder de-activation technology. Sure, you can just not inject fuel into any given cylinder, that’s easy, but that’s hardly efficient with regard to pumping losses. The best way is still going to be deactivating valves at the same time.

      Schaeffler also took the hydraulic variable valve timing and lift invented by Fiat, by buying out the license when Fiat needed money in 2001. They developed it, productionized it and sold it back to Fiat.

      I have no idea who Tula is, but GM relying on some start-up for cylinder deactivation seems like a bold move, when Schaeffler already know what they’re doing. But you never know, there’s no monopoly on good ideas.

      Schaeffler must be chortling all the way to the bank though. Their subsidiary LuK makes the belts and cones for Subaru’s CVT, now selling at record levels. And if someone here can document a failed Subaru CVT (not the crap Jatco in Nissans), I’d love to hear about it. My dealer has had zero problems for years after the initial hiccups.

      Schaeffler are about to introduce electromechanical cam-phasers. So when some OEM crows about that exclusive soon, you’ll know it probably wasn’t their blue-eyed boys who invented it, but a supplier.

      Of course, all this can crash in the mud, too. Look at ZF. Great 8 speed automatic, and the What Were They Thinking 9 speed gracing Chryslers and V6 Acuras.

  • avatar
    Felis Concolor

    Modern direct injection technologies make this system as easy to implement as the software algorithms mentioned in the release. If cylinder n is not required during a particular engine revolution, it’s easy to keep the injector closed and not burn that fuel. You don’t need to mess with the ignition circuit, nor do you need to muck about with more complex mechanical systems, such as collapsing lifter banks.

    • 0 avatar
      cbrworm

      I could be wrong, but I believe the systems work more efficiently if a valve is held open (or both held closed) during the cycle to reduce losses from the compression stroke.

      • 0 avatar
        danio3834

        GM’s Displacement On Demand and Chrysler’s Multi Displacement System collapse the lifters on the 4 “cold” cylinders to keep the valves closed to reduce pumping losses. Of course, fuel injection is shut off as well. There really aren’t may issues with the systems, they function very reliably.

        • 0 avatar
          Felis Concolor

          I haven’t heard of any problems with the existing collapsing lifter tech, but whenever fewer moving parts are involved, I naturally assume greater reliability as that’s another subsystem which is not needed.

          Compared to the 8-6-4 of several decades ago, current cylinder deactivation tech is several orders of magnitude more reliable. And I’d like to see Fiat scale up its hydraulic valve actuation tech to 6 and 8 cylinder applications; a new induction profile is a software tweak away!

      • 0 avatar
        heavy handle

        It’s better if the valves are held closed because the vacuum in one cylinder will offset compression in another. You still get friction losses, but no pumping losses.

  • avatar
    RogerB34

    Skip Fire is a misnomer.
    Should be Skip Injection.
    Deceleration fuel cutoff, DFCO, has been around several years.
    My 05 Honda has it but not the 05 Sable.
    DFCO stops the injectors from firing on deceleration.
    Takes about 12 seconds idle throttle and rpm above 1500.
    Also will reactivate on long downhill idle throttle to maintain cat temp.

  • avatar
    schmitt trigger

    I say good for them, for thinking out of the box and being courageous enough to try a new technology.

    Having said that, I’m not planning on being their guinea pig.

  • avatar
    CoreyDL

    Are they going to use that new gauge design in the photo for the ATS?

  • avatar
    Occam

    What is the advantage of this over forced induction, where the blower can create a higher ‘virtual’ displacement as needed. It would seem that more displacement and forced induction are two ways to do the same thing (bring in more air, adding more fuel to keep the ratios in line, and gaining more power as a result.)

    The V8-6-4 was a good concept that GM fumbled on implementation. The same goes for turbocharging and all-aluminum blocks (F-85 Rocket V8).

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