Mazda IRVINE, Calif.—Despite rumors to the contrary, the internal combustion engine is far from dead. Recently we’ve seen several technological advances that will significantly boost the efficiency of gasoline-powered engines. One of these, first reported back in August 2017 , is Mazda’s breakthrough with compression ignition. On Tuesday, Mazda invited us to its R&D facility in California to learn more about this clever new Skyactiv-X engine, but more importantly we actually got to drive it on the road. What’s so special about this engine then? (credit: Mazda) The idea behind Skyactiv-X is to be able to run the engine with as lean a fuel-air mixture (known as λ) as possible. Because very lean combustion is cooler than a stoichiometric reaction (where λ=1 and there is exactly enough air to completely burn each molecule of fuel but no more), less energy is wasted as heat. What’s more, the exhaust gases contain fewer nasty nitrogen oxides, and the unused air gets put to work. It absorbs the combustion heat and then expands and pushes down on the piston. The result is a cleaner, more efficient, and more powerful engine. And Skyactiv-X uses a very lean mix: a λ up to 2.5. Read 22 remaining paragraphs | Comments

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Compression ignition engines are a big breakthrough—we got to try one