| 4:22 AM EST

Are Two Strokes Better than Four?

A typical internal combustion engine at work in any car or truck today is a four-stroke: intake, compression, combustion, exhaust.
#GeneralMotors #Ford #Navistar


Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

A typical internal combustion engine at work in any car or truck today is a four-stroke: intake, compression, combustion, exhaust. This means that there needs to be things like valves and camshafts and cylinder heads.

Two-stroke engines are simpler. Compression and combustion. Instead of valves, there are ports in the walls of the cylinder for intake and exhaust. The engines are much simpler than four-stroke engines. And smaller. And less expensive. And yet, you’re likely to find a two-stroke engine on a lawnmower or a jet ski, not a car or truck. This is because two-strokes tend to have issues related to producing more pollution and not having the sort of longevity of a four-stroke (you’re not going to see a 100,000-mile warranty on that snow mobile).


Enter Achates Power of San Diego. For the past 10 years the company has been working on the development of two-stroke diesel engines for use in the auto industry.

But these two-stroke engines are wholly unlike those that you’ll find elsewhere. That’s because they’re using a configuration that has two opposed pistons in a single cylinder. According to David Johnson, Achates president and CEO, a man who has diesel experience with Navistar, Ford and General Motors, Achates is solving many of the concerns related to two-strokes, and, because of their approach of having two pistons in one cylinder they have developed an even simpler architecture for what is already more straightforward than a four-stroke.

He says they’re getting the power and the performance. That they’re getting better combustion so there are reduced exhaust emissions. That they’re providing a means through which OEMs can get the kinds of miles per gallon that they need to make reaching CAFE affordable for both the manufacturer and the consumer.

And David Johnson talks about this and more on this edition of “Autoline After Hours.”

Lindsay Brooke of SAE International joins John McElroy and me in the studio to talk with Johnson.

In addition to which, Brooke, McElroy and I discuss a variety of subjects, including John’s lunch with Dan Gurney, my trip to Wolfsburg to drive the eGolf and the GTE, and other automotive-related topics. Like the new Voltec powertrain for the forthcoming 2016 Volt.

All of which you can see here:

Related Topics


  • Breaking Down the Chevy Bolt

    Sandy Munro and his team of engineers and costing analysts at Munro & Associates were contacted by UBS Research—an arm of the giant banking and investment firm—and asked whether it was possible to do a teardown and cost assessment of the Chevrolet Bolt EV.

  • 2016 Prius: The Fourth Generation

    The little car that could still can. And this time as a car that not only gets great fuel economy, but which has ride and handling that makes it more than an econo-box (and its styling is anything but boxy).

  • Making the Case for Lithium-ion Batteries

    Lithium-ion batteries have become the technology of choice for EVs, and falling costs and rising energy levels could keep them on top for nearly two decades.