Mazda SkyActiv is a novel approach to fuel efficiency; will it work?

Mazda is a small Japanese car company – fifth in Japanese-brand U.S. sales behind the "Big Three" of Toyota, Honda and Nissan and just behind distant-fourth Subaru – that prides itself on being different, more youthful and more fun to drive. Hence its "Zoom-Zoom" marketing theme and the goofy toothless grin on the faces of most recent Mazda products.

Now Mazda is taking a very different approach to meeting government and customer demands for fast-increasing fuel efficiency that may (or may not) pay off. Instead of betting billions on plug-in and hybrid vehicles, Mazda's approach is a comprehensive effort to substantially increase the efficiency of every element of every vehicle, beginning with engines and transmissions and continuing through bodies and chassis.

Mazda has been working on these efficiency-enhancing technologies for half a decade and is now applying them – beginning with new powertrains in its revamped 2012 Mazda3 compacts (pictured), which join the vaunted 40-mpg highway economy club – under the marketing name "Skyactiv." Some critics say the name is dumb. To some it may conjure images of flying cars or clear, blue skies over active lifestyles. Mazda says it means, "The sky is the limit."

But what really matters is, how well will it work? And will it sell more Mazdas?

"Our goal is to improve fuel economy globally by 30 percent," says Mazda Motor Corp. Product Planning executive officer Kiyoshi Fujiwara. "And our answer is still the ICE. Our top priority is to radically improve this technology."

So SkyActiv begins with internal combustion engines, gasoline and diesel, made substantially more efficient through innovative new technologies. Yet, he says, "SkyActiv will retain our 'Zoom-Zoom' brand character."

Fujiwara adds that SkyActiv implementation will employ a "building block" strategy of launching efficiency-enhancing technologies progressively, beginning with the least expensive and leading eventually (inevitably) to vehicle electrification to meet extremely aggressive corporate average fuel economy (CAFE) requirements. The key is putting off the latter until those technologies are further developed and somewhat more affordable.

Another key is applying SkyActiv technologies to a common architecture with enough flexibility to underpin most (maybe all) Mazda products. "Using a bundled product planning approach," he explains, "we can integrate SkyActiv technologies into all Mazda products over time, by ourselves [no OEM technology partners] and remain affordable."

mazda skyactiv

Interestingly, both global SkyActiv-G gas engines and SkyActiv-D diesels share the same 14:1 compression ratio. That is the world's highest CR for a gas engine today and the world's lowest for a diesel. But how does lower compression make a compression-ignited diesel more efficient when the opposite is true for a spark-ignited gas engine?

"The ICE still has substantial losses," says Mazda powertrain development manager Ritaro Isobe. "We needed to reduce them further. Our vision was ideal combustion, and we have applied technology innovation to achieve that."

He calls the 14:1 CR "groundbreaking," though it's a lesser 13:1 in U.S. engines to accommodate our 87-octane regular gas. A "breakthrough" combination of technologies – including direct multi-hole injection, dual VVT, new-design pistons, a unique 4-2-1 exhaust system, shorter combustion duration and delayed ignition during start-up – prevents knock.
Mazda says the 2012 Mazda3's new 2.0L SkyActiv gas four-cylinder consumes 15 percent less fuel than its same-size predecessor – roughly equivalent to a 2.2L conventional diesel – and makes 15 percent more torque, especially in the low-to-mid-rpm range. It is also 10 percent lighter and has a whopping 30 percent less internal friction.

For a new 2.2L SkyActiv turbodiesel, the low CR improves efficiency by enabling better fuel mixing and a higher expansion ratio. It also allows the engine to weigh 10 percent less due to its lighter block, crankshaft, pistons and connecting rods. It has 20 percent less internal friction vs. Mazda's previous 2.2L diesel four and delivers 20 percent better fuel economy, improved low- and high-rpm torque and more power at a high (for a diesel) redline, not to mention (U.S. Tier 2, Bin 5) emissions compliance without an expensive NOx catalyst.

He adds that there were two major issues to overcome with the low-compression diesel: difficult cold start and misfiring during warm-up. Mazda's solutions include piezo injectors, ceramic glow plugs, a two-stage turbocharger and variable-lift exhaust valves. The U.S.-market 2.2L SkyActiv-D should be available by early 2013.

The new Mazda3 compacts also offer a choice of efficiency-enhanced SkyActiv six-speed manual or six-speed automatic transmission. The former is a substantial 30 percent lighter than its predecessor, with shorter throws and less friction. The latter delivers smoother launch, quicker shifts, more direct feel and up to seven percent better fuel efficiency.

What the new Mazda3 does not have (because it's not an all-new design) are the SkyActiv body or chassis. These will debut on the 2013 CX-5 small crossover. Mazda says the CX-5 structure is eight percent lighter with 30 percent greater rigidity to optimize both handling dynamics and crash performance. The suspension is 14 percent lighter and incorporates, among other advancements, highly efficient electric power-assisted steering (EPAS).

mazda skyactiv engine

We test-drove mid-size Mazda6 sedan development "mules" powered by early versions of SkyActiv 2.0L gas and 2.2L diesel engines with both SkyActiv transmissions, and they delivered on Mazda's promises. Both engines were smooth, responsive, reasonably powerful and torquey enough to be fun to drive ("Zoom-Zoom"), and all four combinations seemed subjectively more satisfying than the ones they will replace. Most impressive was the surprisingly high-rpm diesel driving through the manual six-speed.

Of course, every automaker is working hard on powertrain and full-vehicle efficiency from roof to tire patch. But Mazda is betting that its major competitors' enormous investments in EVs, hybrids, fuel cells and other advanced technologies will limit their near-term investments in ICEs, transmissions, bodies and chassis enough that key competitive advantages can be gained and CAFE requirements met with much-improved conventional powertrains. At least for the next few years – until it, too, will have to electrify to meet CAFE.

That said, we just learned that the 2012 Mazda3's SkyActiv gas engine has been named one of Ward's Auto World's 2012 Ten Best Engines. Nice first step!

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