Mazda pins improved mpg on Skyactiv 2

Engines to debut around 2020, will boost fuel economy 30%

The Mazda6 sedan uses a six-speed as rivals add gears.

YOKOHAMA, Japan -- Mazda has ambitious plans for a generation of engines debuting around 2020 that would achieve 30 percent better fuel economy than the current line of Skyactiv engines the company has only just begun rolling out.

The new gasoline and diesel engines, called Skyactiv 2, will focus on improved internal combustion, said Mitsuo Hitomi, executive officer in charge of powertrain development.

"If we want to dramatically improve fuel economy from here, the only route is through lean burning," Hitomi said during a briefing at Mazda's Yokohama technical center, where he and other engineers provided the first details of the future powertrain strategy.

Mazda didn't say when it would introduce the engines. But Hitomi said Mazda needs the technologies to meet tougher European carbon dioxide emissions standards of 95 grams per kilometer in 2020 and 65 grams per kilometer in 2025.

"The next step is the 2020 European regulations," Hitomi said. "It must help us with that."

The plan targets another big leap in Mazda's powertrain performance and would come less than a decade after the first fuel-saving Skyactiv engines appeared in 2011.

Those engines, which are still gradually being spread across the lineup, scored big fuel economy gains for Mazda by pairing direct injection with higher compression ratios.

The new gasoline engine under development would be 30 percent more efficient than those Skyactiv powerplants, which made their U.S. debut in the Mazda3 sedan. Since then, Skyactiv engines have been added in the Mazda6 sedan and CX-5 crossover.

Mazda engineers aim to eke the gains by cranking up the engine's compression ratio to 18:1, from a current level of 14:1. Higher compression tends to improve fuel economy because they can achieve the same combustion temperature with a leaner mix of fuel. Mazda says the 14:1 ratio in its first-generation Skyactiv gasoline engine is the world's highest.

Mazda's determination to squeeze better performance from the internal combustion engine diverges from the strategy of bigger rivals. Mazda, one of the world's smallest global brands, is playing to its strengths in a tried and true technology, while competitors with bigger r&d budgets dabble in a range of alternative drivetrains, such as hybrids.

Mazda also invests in electrified drivetrains to meet increasingly stringent emissions standards. But its push has been mainly into engine stop-start or brake regeneration technologies. It licenses its hybrid drivetrain system from Toyota Motor Corp.

Skyactiv 2, then 3

Hitomi also outlined plans for a Skyactiv 3 lineup further in the future.

That system may help Mazda comply with 2025 emissions targets.

It would limit the fluctuation of heat in the combustion chamber to reduce losses from exhaust and cooling, Hitomi said. That would make more energy available for powering the wheels.

He did not predict the level of increased efficiency expected from this engine family. But the goal is achieving well-to-wheel carbon dioxide emissions on a par with electric vehicles.

The Skyactiv 2 engine will use homogeneous charge compression ignition, known as HCCI. That technology compresses the fuel-air mixture to such a high pressure and temperature that it ignites by itself without requiring a spark, similar to the way a diesel engine operates.

HCCI allows for more complete fuel combustion and lower nitrogen oxide emissions.

Mazda says HCCI would allow the company to forgo continuously variable transmissions or the need to invest in new multistage automatic transmissions. While rivals are moving to automatic transmissions with eight or more speeds, Mazda's Mazda6 flagship sedan uses a six-speed. Mazda can get by with fewer gears because its engines will be that much more efficient, it says.

Hurdles remain

But hurdles remain for the HCCI technology envisioned for Skyactiv 2.

For starters, engineers must expand the range of engine speeds at which HCCI can work. If the engine is revving too quickly, there is the risk of misfire because of the high number of revolutions. If it revs too slowly, it can misfire because of low temperatures.

Engine cooling is a challenge for engineers because of the HCCI's high temperature and pressure. Finally, the engines are more fickle about fuel and perform differently depending on fuel properties.

Mazda's new CEO Masamichi Kogai told Automotive News in November that refining the internal combustion engine will be the main push for Skyactiv 2. That is partly because it is a cost-effective approach with a proven technology. He promised that the results would be as dramatic as those achieved with the current Skyactiv system.

"We will base it on the internal combustion engine and that's where we will put the emphasis," Kogai said. "The evolution will be the same degree as the first generation."

You can reach Hans Greimel at -- Follow Hans on Twitter: @hansgreimel



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