Dear MOby,

Why are camshafts still used? I’d think that valves could be controlled by small electronic controllers and be directed to open and close with much greater accuracy (as well as being more “condition-dependent”) than the generally fixed operation they follow based upon a cam profile.

In addition to more precise control, it would probably be lighter and have minimal or no spinning kinetic energy to take account of. Probably also provide engine packaging advantages as well.

And changes would be much easier/quicker to make and test – no need for casting a new cam to test how profiles might work. And, it could obviously tie in with the motorcycle’s ECU, IMU, and any other “U’s” for even finer granularity of the functions it provides.

Walter

(Walter asked this in Comments after Ask MO Anything three weeks ago, in which we explored whether the IMU [inertial measurement unit] actually serves a useful purpose.)


Evans Brassfittings actually came up with the answer to this one immediately: It’s called the two-stroke engine. You don’t have to search much to stumble across things like Arctic Cat’s new 6000 C-Tec2 direct-injected two-stroke on our sister site Snowmobile.com, where our friend Jerry Bassett writes “modern and evolving direct injected two-stroke technologies led by companies such as Rotax, Evinrude, Orbital of Australia, Synerject in the US and others can point to the fact that two-strokes can be as emission friendly and miles per gallon efficient as four-strokes.”

Arctic Cat’s 2014 design uses reed valves instead of intake valves, and a two-stage fuel injection system that also introduces fuel (and lubricant) into its transfer ports via slots in the rear of the pistons at high rpm. Arctic Cat rates the 600 at 123 hp at 8100-8300 rpm. They also say it weighs 10 pounds less than competing direct-injection engines, so it’s way lighter than anything with cams, drive gear, and valves. You can see the compactness, and AC says it’s also Tier III EPA compliant – which we believe is not quite CARB but close....

Arctic Cat’s 2014 design uses reed valves instead of intake valves, and a two-stage fuel injection system that also introduces fuel (and lubricant) into its transfer ports via slots in the rear of the pistons at high rpm. Arctic Cat rates the 600 at 123 hp at 8100-8300 rpm. They also say it weighs 10 pounds less than competing direct-injection engines, so it’s way lighter than anything with cams, drive gear, and valves. You can see the compactness, and AC says it’s also Tier III EPA compliant – which we believe is not quite CARB but close….

BRP (Bombardier Recreational Products) introduced its E-TEC technology in Evinrude outboard engines in 2003 (and won the Clean Air Technology Excellence Award from the U.S. Environmental Protection Agency), then later adapted E-TEC for Ski-Doo snowmobiles. Its latest E-TEC 800 two-stroke Twin (2010) makes around 160 crankshaft horsepower. Meanwhile the latest 800 H.O. two-stroke Twin Polaris put in two of its sleds for 2015 also makes around 160 horses. Correct, the same Polaris that owns Victory and Indian.

Reading between the lines of the reviews, it seems like the finickiness of some of these engines has been or is being worked out, the biggest one being that they’re pretty thirsty. On a snowmobile, though, my very limited experience is that you’re at WOT a lot more than on a motorcycle (except when you’re on a racetrack). Anyway, it’s interesting to contemplate an engine like this in a 400-pound sportbike, but I’ve only met blank looks anytime I’ve brought up snowmobile engines at Victory affairs.

If you must have four strokes and good old-fashioned poppet valves, Walter, we did bump into this Koenigsegg Freevalve video on the www, illustrating a camshaftless head design the Swedish supercar maker has been working on for over a decade.

082216-ask-mo-anything-camshaft-Koenigsegg-freevalve

Though the Freevalve engine retains vestigial valve springs like the ones on a Desmo, actual valve events are controlled by electronically actuated pneumatic and hydraulic systems, meaning there’s virtually no limit to this engine’s ability to customize valve timing for any combination of rpm or load – or shut off cylinders at cruise, etc.

How close is it to production? Close enough to take a Jalopnik reporter for a ride in a Saab equipped with the Freevalve engine a couple years ago. Anyway, nothing is new under the sun, and camless technology is a thing many manufacturers have been experimenting with for years. Good old Wikipedia is a good place to start investigating if you need to know more.


Direct your motorcycle-related questions to AskMoAnything@motorcycle.com, though some say we’re better at non-motorcycle-related ones…

  • Starmag

    Camshafts are still more cost effective and many people hate the sound of two strokes? (Not me.)

  • Donnie
  • Born to Ride

    Really enjoyed the portion on free valve motor. Really sweet engineering. I always wondered how long it would be before someone would come up with a individually actuated valve system. The problem is that solenoids that are strong enough to move the poppet valves fast enough and consistently enough would be rather large. Interesting stuff. I’m liking this “ask MO” column more and more

  • Dootin

    I am so ready for a sub 400 pound, 100 HP two stroke.

    • KYspeaks

      There’s the Suter MMX 500 if your bank account has loads of zeros

  • halfkidding

    I doubt 2 strokes can overcome emissions restraints, ie. burning oil, or efficiency constraints, ie. low compression + twice as many intake cycles.

    Camless poppet valves have been worked on for a long time. They are sort of here now but can they be reliable and cost competitive within even 10 years? I doubt it. I read about a prototype engine that was working 20 years ago. It’s still essentially vapor ware.

    I have no numbers but I will guess that the energy efficiency of camless isn’t all that much better than cams. The real promise in infinite cam timing. A great thing to be sure but at what point does it make economic sense? I’d say when gasoline is truly in short supply. 5 years, 20, 40, pick your number but it will happen.

    • toomanycrayons

      “I have no numbers but I will guess that the energy efficiency of camless isn’t all that much better than cams. Joules per valve actuation. The real promise is infinite cam timing. A great thing to be sure but at what point does it make economic sense? I’d say when gasoline is truly in short supply. 5 years, 20, 40, pick your number but it will happen.”-halfkidding

      Gentlemen, we have the science of vapours, happening:

      “Scientists solve puzzle of converting gaseous carbon dioxide to fuel

      Saving the planet from climate change with a grain of sand”

      https://www.sciencedaily.com/releases/2016/08/160825113217.htm

      Now, if more time could be devoted to comfortable seats, bug-free visors, and numb-free hands, the future would be perfect…

  • john phyyt

    What an excellent article. And since a lot of amps would be required could I ask that you use some of this electricity to turn a cool air intake turbine to make lots more power low in the revrange ( combines with optimum valve timing ) where conventional turbos do nothing.

  • Alexander Pityuk

    Solenoids are just too slow for this job. They naturally want to keep the amperage constant, that’s why they unwillingly turn on and off. They are often used as electrical filters for that reason. Big no-no.
    What we are left with are pneumatic and hydraulic actuators. And of course they are much more complicated and much less reliable than medieval chain-driven camshaft.

  • Auphliam

    I have a question for my own education; Why is the lubricant required in the fuel in the two-stroke and not the four? All things being equal, couldn’t a traditional four stroke oiling system provide enough lubrication and cooling if all you changed was the intake method?

    • Gruf Rude

      The 2-stroke “breathes” through its crankcase, so the high-pressure oiling system for the main and rod bearings used in the sealed crankcase of a 4-stroke is impossible. Instead, the bearings in the 2-stroke are oiled by the lubricant mixed into the fuel.

      • Auphliam

        Ah, okay. Thank you.

    • LogicDude

      Thanks to your post, and the random event of my doing a search for “Ducati” on this thread, I saw within your post that “Education” contains the word “Ducati.” I’m an educator. I think the implication is undeniable. Time to talk with the wife.

  • Douglas

    Back in the ’60’s, a company called Schaller (I think), was mfg double-lobed cams that turned at 1/4 engine speed, rather than half. That’d seem to reduce rotary inertia and reduce wear & friction somewhat, especially w/rollers (which I don’t think had appeared yet back then). Don’t know how effective that’d be in scooter engines, and not much was reported on this design after promising tests were done (a rumor was that one of the bigger cam grinders, Isky, Howard’s, Crane, etc, bought it out and killed it), but it might’ve been worthwhile. Any thoughts?…

  • Walter

    Thanks for the follow-up.

    So: a bit more power, a bit better economy, and lowered emissions. Not mentioned is the weight savings removing the cams, belts, gears, etc. (not such a big deal for a car, but more important for a bike). Power consumption seems a bit high,and durability is still unknown. But hey, early FI had some issues that needed to be worked out before it became as good as it is. So I remain optimistic that it is probably just waiting for the right breakthrough.

    Thanks again.

  • paultd

    I noticed that the article didn’t answer or even address the question of why we still use camshafts? The short answer is that camshafts are currently the best solution to valve actuation.