Mazda Skyactiv-D arrival delivers on diesel promise, homogeneous-charge Skyactiv-X next

Mazda finally delivers on its longstanding promise to bring its low-compression diesel to the U.S., and homogeneous-charge gas engines should follow soon.

Mazda announced the long-awaited arrival of its Skyactiv-D diesel engine to the U.S. at the New York International Auto Show (NYIAS) last week. The 2.2L twin-sequential turbocharged 4-cylinder diesel is available for pre-order now in the highest AWD trim of Mazda’s best-selling vehicle, the 2-row, 5-seat Mazda CX-5 SUV (top). The 2019 model with the diesel engine has a starting MSRP of $41,000 – a $4K premium over the equivalent gasoline trim – with deliveries expected to begin this summer.

Mazda also announced that the same Skyactiv-D engine will be available “soon” in the Mazda6 sedan, and confirmed that its Skyactiv-X homogeneous-charge gas engine will go on sale in Europe before the end of 2019. Mazda claimed that after the rollout in Europe, Skyactiv-X engines will then come to markets (including the U.S.), which already feature Mazda’s Skyactiv-G high-compression gasoline engines.

50-state-compliant diesel
Mazda said much of the delay in launching the diesel engine is attributed to time spent working with U.S. federal and state agencies to ensure emissions compliance, including the California Air Resources Board (CARB). “During the homologation phase of certification, we have collaborated with CARB on what real driving emissions conditions in the U.S. should be,” explained Ichiro Hirose, senior managing executive officer of R&D, who’s in charge of Mazda powertrain development. “We actually studied that deeply, and together with CARB considered what driving conditions should be guaranteed.”

Thanks to its lower compression ratio, the Skyactiv-D engine was initially intended to forego certain aftertreatments, and was Euro V and Euro VI compliant without selective catalyst reduction (SCR). Mazda recently added SCR to the 2.2L Skyactiv-D engine in Europe to meet the new, stricter Euro-6D standards, and for the even stricter standards in the U.S., Mazda has added a dedicated NOx storage catalyst (NSC).

Compression-ratio family
The new 4-cylinder is part of Mazda’s Skyactiv program, which aims to lower the compression-ratio of diesel engines (Skyactiv-D) and raise the compression ratio of gasoline engines (Skyactiv-G). Both the gas and diesel variants operate with compression ratios around 14:1. The upcoming Skyactiv-X homogeneous charge compression ignition (HCCI) gasoline engine is expected to have a compression ratio around 16:1.

The new diesel is designed to rev higher and more freely than a typical oil-burner, with a 5500 rpm redline. In the CX-5, the 2.2L Skyactiv-D is expected to produce 168 hp at 4,000 rpm, and 290 lb-ft at 2,000 rpm with an EPA estimated mpg rating of 27/30/28 (cty/hwy/comb). The 2.2L 4-cylinder features a unique, two-stage twin turbocharger with both turbines sharing a routable hot side (see video, above). Energy is channeled to the smaller turbo at lower rpm, and the larger turbo features variable geometry to further improve response and high-rpm flow.

Many program synergies
Credit Mazda for hanging tough on their promise to deliver a diesel in the U.S., a market where several other manufacturers have called it quits. Mazda might quote its “challenger spirit”, but some of this is likely due to the scope of Mazda’s Skyactiv program, which sees complementary R&D between the gas and diesel programs.

“There are many positive synergy effects,” Hirose explained. “Usually for a big OEM, the diesel and gasoline development divisions are completely separate. However at Mazda, the same division is working on both. During the diesel process, we made various breakthrough findings that were utilized for Skyactiv-X, and likewise for Skyactiv-X development, technologies that were utilized for diesel. For example, for Skyactiv-X, we are planning to introduce a very high-pressure injection system, a concept that came from the diesel injection system.”

HCCI next
According to Mazda, a 2.0L HCCI Skyactiv-X engine will debut in Europe before then end of this year. “Given the timing, you can imagine that we are already at the homologation stage, and have completed technology development,” Hirose said. “Our plan is we will introduce Skyactiv-X first into Europe in the latter half of this year, then one by one to various markets after Europe, into the markets where we have introduced Skyactiv-G.”

How does Mazda see the three Skyactiv applications existing in its lineup? “Diesel is suitable for big SUVs for example, its advantage is big torque and long range,” Hirose said. “We are planning to introduce a 2.0L Skyactiv-X that will fit with a compact vehicle. And as for Skyactiv-G, it will have a best match with certain product characteristics, so we will consider the different segments and differentiate the adaptation of these technologies.”

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