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"  Relatively simple and lightweight, two-stroke engines (found in chain saws and outboard motors) would be great in cars and trucks, if they weren&amp;#039;t so dirty. &amp;quot;I probably spent $50 million of GM&amp;#039;s money proving two-strokes don&amp;#039;t work in automobiles,&amp;quot; says General Motors veteran Don Runkle. The Opposed-Piston, Opposed-Cylinder (OPOC) engine developed by EcoMotors&amp;#039; Peter Hofbauer changed Runkle&amp;#039;s mind so thoroughly that he became the company&amp;#039;s CEO. As in other flat engines (sometimes called boxer engines for the way their pistons resemble two fighters trading jabs), OPOC&amp;#039;s pistons move horizontally. Hofbauer&amp;#039;s aha! moment came one day when the former Volkswagen engineer was pondering the shortcomings of VW&amp;#039;s boxer engine. &amp;quot;I thought, my God, if you just replace the cylinder head with a moving piston and cylinder ports, it might be less complicated.&amp;quot; It is\u2014by a long shot. The engine requires less than half the parts of a similar four-stroke engine and is 30 percent lighter. The net result, says Hofbauer, is a 15 to 50 percent increase in energy efficiency, depending on the configuration. And thanks to its unique architecture and several key innovations, the OPOC releases far fewer emissions than a typical two-stroke. With a 240-hp diesel prototype, EcoMotors is focused now on the truck market; last February the company signed a licensing agreement with Navistar. &amp;quot;When the economy has recovered, the world will add 85 million combustion engines for cars and light trucks,&amp;quot; Hofbauer says. &amp;quot;If we can offer an engine that is efficient and competitive in production costs, it will be a success.&amp;quot;  TURBOCHARGER An electric motor mounted to the blower&amp;#039;s shaft quickly spools the compressor for a fast boost; in reverse, it generates electricity off the exhaust flow. Plus, it manages exhaust pressure to minimize emissions.  STEEL CONNECTING RODS Long steel connecting rods join the outer pistons to the crankshaft. With two pistons working off one combustion event, the engine behaves as though it has a long stroke\u2014utilizing more of the available energy and increasing efficiency. Yet the crankshaft remains compact and therefore lighter. CRANKSHAFT The engine is modular, and the crankshaft of the cylinder pairs can be connected by a clutch. For highway cruising, unneeded cylinders can simply be idled and then engaged again for passing.  CYLINDER Gases flow in and out of the cylinder via ports in the walls, saving the complexity and weight of cylinder heads. The design of the intake and exhaust systems and combustion chamber keeps excess unburned fuel from exiting the exhaust port, reducing emissions.    &amp;amp;lt;&amp;amp;lt;&amp;amp;lt; 10 Brilliant Innovators    Ready-Made Blood Vessels &amp;amp;gt;&amp;amp;gt;&amp;amp;gt;    "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/cars/a7167/the-lighter-better-more-efficient-two-stroke-engine/>