August 9, 2011

Mazda SkyActiv-G gasoline engine.

Article and photos by Paul Williams

Vancouver, British Columbia – You’ll soon be hearing a lot from Mazda about Skyactiv, Mazda’s new technology to lower fuel consumption, enhance vehicle dynamics and reduce emissions.

No, Skyactiv doesn’t mean Mazda’s getting into the aviation business; the term refers to the expression, “the sky’s the limit.” But unlike larger competitors that have the resources to develop a range of alternative propulsion technologies — like hybrids, electric vehicles, plug-ins and hydrogen fuel cells — the smaller Mazda (annual global sales 1.2 million) has chosen to focus on the familiar, and innovate.

True-to-form, though, the company that perfected the rotary engine and invented the term “zoom-zoom” to describe the sporty character of its vehicles is moving in what some may consider unexpected (but by no means radical) directions. Nonetheless, the experience of driving some Skyactiv prototype vehicles in Vancouver would suggest that consumers will definitely benefit from Mazda’s new technology.

Specifically, Mazda believes there are significant opportunities for further development of gasoline and diesel engines, along with benefits to be gained from transmission and chassis refinement. It has consequently spent several years completely rethinking the company’s existing powertrain and chassis technology, culminating in a suite of developments that will be incrementally introduced in new Mazda vehicles in the coming years.

Mazda SkyActiv-D diesel engine.

Yes, you did read “diesels.” Mazda confirms it will be bringing its new diesel engines to Canada — expect an early 2013 timeframe — although we don’t have commitments on exactly what vehicles will receive the option. Our diesel-powered test vehicles in Vancouver were Mazda6 sedans (mostly in test “mule” form), and the engine works very well in those. But the upcoming CX-5 compact SUV would be a good fit, and it was certainly hinted that this is a possible application. Actually, any vehicle in Mazda’s line-up is a good fit, given that the new diesel is expected to generate 310 pound-feet of torque at 2,000 rpm, while sipping fuel.

In addition to their power and fuel economy, the upcoming Mazda diesel engines — called Skyactiv-D — also have advantages when compared with Mazda’s diesels currently available in Europe and Asia, and diesels from other manufacturers that require “after- treatment” technology to reduce emissions to acceptable levels. Due to its low compression ratio of 14:1 (a breakthrough technology, according to Mazda, and the lowest for a diesel engine) lighter weight, innovative piston shape, 30 per cent reduced internal friction and innovative combustion management, the Skyactiv-D will comply with Tier2 Bin5 emission regulations without after-treatment technology to remove soot, carbon dioxide and other pollutants. This makes the Skyactiv-D fully compliant in North America.

From the consumer perspective, class-leading low- and high-end torque, faster diesel warm-up times and a 20 per cent reduction in fuel consumption (when compared with Mazda’s current diesels used in other markets) should be very popular indeed.

From my perspective, it’s about time, as you’re unlikely to find a Canadian automotive writer who’s experienced the excellent diesel-powered vehicles in Europe and doesn’t think the technology would do well here (not to mention that Canadian consumers have demonstrated they’ll buy every Volkswagen TDI product the company can supply).

Mazda6 SkyActiv test “mules.

Complementing the diesel engines, Mazda gasoline engines are also receiving the Skyactiv treatment, although in a gasoline engine (as opposed to a diesel) it’s a high compression ratio that’s coveted, according to Mazda Skyactiv Program Manager Niini Susumu. “With gasoline engines, every engineer knows that a high compression ratio is key to power and fuel efficiency” said Mr. Niinai in Vancouver.

At highway speeds, he explained, the gasoline engine is working at 20 to 30 per cent efficiency, and in the city it’s working at only 10 per cent efficiency. Consequently there is significant improvement in efficiency available in the gasoline engine, and given that (according to Mazda) 80 per cent of vehicles will still be powered with gasoline engines in 2020, the argument to improve this technology is compelling.

Mazda engineers therefore set themselves the task of increasing efficiency in a number of ways, starting with raising the compression ratio of Skyactiv-G engines to an industry-high 14:1 (a Ferrari is 12.5:1 and the average family car ranges from 9 -11.1).

You may ask why, if simply raising an engine’s compression ratio is the key to efficiency, other manufacturers have not attempted this with mainstream vehicles. The answer is that engine knocking is associated with higher compression ratios and that developing the technology to manage this has presumably not been commercially feasible.

However, Mazda has managed to control engine knocking by using an innovative piston cavity design and fitting a sophisticated four-into-two-into-one exhaust manifold. The Skyactiv-G engines also feature lighter materials, more precise engine tolerances, and other techniques to mitigate misfiring, exhaust, cooling, mechanical and pumping loss in the engine’s operation. It is, as Mazda describes Skyactiv-G, “the ideal combustion engine.”

But we won’t see the available 14:1 Skyactiv-G engines in North America as our low-octane regular-grade fuel is not sufficient to facilitate optimal operation. Our Skyactiv-G engines in their final form will operate at 13:1, thankfully enabling consumers to use regular-grade gasoline, rather than more-expensive premium.

Compared with Mazda’s current 2.0-litre engine, the result of all these developments is a 15 per cent increase in fuel economy and torque and a corresponding reduction of emissions in Skyactiv-G engines, the first iteration of which (initially without the special “header”) will be seen in the new Mazda3, debuting this fall.

Brief drives in the mostly right-hand drive test “mules” in West Vancouver demonstrated the smoothness and quietness of both Skyactiv-D and G engines, along with the diesel’s surprising power. In comparison with current examples, both engines were noticeably superior.

[Source: Autos.ca]