Categories: Ask MO Anything
31 | Updated 22

Ask MO Anything: Why Do We Still Use Camshafts?

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 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, 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….

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.

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, though some say we’re better at non-motorcycle-related ones…