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.

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).

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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: