Hyundai reckons its 'Smart Stream' engines can be the most efficient engines ever built.

Hyundai isn’t ready to abandon internal combustion engines just yet – the car maker has revealed its new engine technology at the International Powertrain Conference in Korea. The company says that its experimental Smart Stream engines have the potential for up to 50 percent thermal efficiency – more efficient by a long margin than anything else on the market. 

One of Hyundai's major innovations is Continuously Variable Valve Duration that times the opening and closing of the valves depending on the driving mode. There’s also a new eight-speed wet dual-clutch transmission.

The company showed off four engines and two transmissions making using of the Smart Stream innovations at the conference – the technology will arrive first on petrol and diesel versions of a 1.6-litre engine, before spreading to cover 10 petrol engines, six diesels and six gearboxes by 2022.

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If Hyundai can actually achieve its goal of 50 percent efficiency from an internal combustion engine that’s on sale to the general public, it would be a major breakthrough – thermal efficiency references the amount of energy produced from a given amount of heat, and in the real world it means getting the most out of every drop of fuel.

Mercedes-Benz recently revealed that its Formula 1 engine had achieved more than 50 percent thermal efficiency for the first time, which made the powerplant the most efficient mill ever seen in racing. This was factoring in the electric hybrid system that recovers waste energy from the exhaust. The version of the F1 engine used in the Project One hypercar achieves a still-impressive 43 percent efficiency. By comparison, the naturally aspirated engines formerly in F1 only mustered around 30 percent efficiency.

Nothing on the road has come close to this level. For example, when the latest Toyota Prius arrived, Toyota promoted the 1.8-litre four-cylinder powertrain’s 40 percent efficiency.