U.S. may have to wait for Mazda's Skyactiv-X

YOKOHAMA, Japan — Mazda's new Skyactiv-X engine is a mild-hybrid technological tour de force. But it may be a while before the system shows up in the U.S. market.

Mazda Motor Corp. is still considering how and when to bring the ultra-efficient, high-torque powerplant to its biggest market, engineers working on the next-generation powertrain say.

One problem is the added cost of all its high-tech add-ons. But the bigger consideration is that the current Skyactiv-X engine might not be big enough for U.S. driving needs.

The Japanese carmaker's latest engine technology is currently deployed only in a four-cylinder 2.0-liter gasoline engine that went on sale in the Mazda3 small car last year in Europe and Japan.

The same engine was also deployed in the CX-30 compact crossover for Japan starting last week.

But Eiji Nakai, Mazda's executive officer for powertrain development, said that engine might be too small for the U.S. The U.S. version of the Mazda3, for example, comes only with a 2.5-liter powerplant.

Speaking at a Skyactiv-X test drive here last week, Nakai said Mazda is conducting computer simulations of applying Skyactiv-X technology to engines with bigger displacements.

"We think this Skyactiv-X can be used for larger engine displacement in the future, in line with our product planning," he said. "This technology is applicable to other engine displacements."

Mazda engineer Yoshiaki Yamane said such powerplants could better suit driving habits in the U.S., where drivers prioritize power for high-speed, expressway driving over fuel efficiency.

"Maybe U.S. customers require more power, because fuel economy is not the top requirement," said Yamane, a powertrain engineer who worked on the Skyactiv-X setup.

Mazda is developing a new large-vehicle architecture that will arrive in the fiscal year ending March 31, 2023. That platform is expected to accommodate a larger-displacement Skyactiv-X engine.

Skyactiv-X represents Mazda's push to develop a more fuel-efficient, yet spunky, engine line.

It harnesses a technology Mazda calls spark-controlled compression ignition, which blends the fuel economy of a gasoline engine with the power of a diesel. Mazda says Skyactiv-X technology delivers sizable improvements in fuel economy and torque, along with smoother acceleration.

In the Japan-market Mazda3 sedan, Skyactiv-X is the top option of four powertrains offered, stickering 27 percent higher than the base 2.0-liter Skyactiv-G gasoline engine. It achieves a 9 percent improvement in fuel economy and a 15 percent increase in horsepower.

The advancement comes thanks to a host of pricey technologies.

For starters, there is the complicated high-pressure combustion system that requires a special cylinder pressure sensor to help time the exact moment of spark ignition. It also needs a high-pressure fuel-injection system, similar to a diesel common-rail setup. Add to that an exhaust gas recirculation system and a three-way catalyst with a gasoline particulate filter.

Then there is the Skyactiv-X supercharger. The supercharger is not for delivering extra power but for forcing air quickly into the cylinder for a super-lean fuel-air mixture.

Finally, Skyactiv-X uses mild-hybrid technology. It bolts on a regenerative braking system, a DC/DC converter and an integrated starter generator. Powering the system is a 21.6-volt lithium ion battery supplied by Toshiba that is tucked under the front floorboards.

Without the extra electrification, the overall fuel economy of the Skyactiv-X system would be about 4 percent lower, Yamane said. But the technology does more than eke out extra miles.

The mild-hybrid system also provides a more silent, vibration-free restart from idle stop, and it facilitates faster and smoother gear shifting. The electric motor assists gear shifting by automatically slowing engine rpm during upshifts to mesh it more quickly with the next gear.

"It makes for a more direct feel," Yamane said. "The driver always feels they are in control."