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Mazda details SkyActiv path

Aiming high: Mazda's new CX-9 is heralding the next-generation of SkyActiv II engines but the technology could go far further than the new turbocharged 2.5-litre SkyActiv-G four-cylinder.

SkyActiv II diesel and adiabatic engine on the way, but no Mazda DCT or nine-speed

27 Jun 2016


MAZDA has outlined some of its ambitious technological goals for the future and says that among more attainable targets, its aspiration to create an adiabatic engine is more than just a conceptual fantasy.

If the Japanese car-maker pulls off the holy grail of internal combustion, it will have its hands on the potential to build, far and away, the most efficient petrol and diesel engines the automotive world has seen.

Heat energy loss to the cooling and exhaust system of today's isothermal engines is the arch enemy of thermal efficiency and fuel economy, but the adiabatic engines Mazda has in its sights will run with no energy transfer, it says.

While the best thermal efficiency figures modern car engines can muster is at about the 40 per cent mark, the still theoretical adiabatic engine has the potential to function closer to 90 or 100 per cent, with the associated benefits to fuel consumption.

Speaking at the demonstration of Mazda’s new G-Vectoring technology in California, Mazda North America vehicle development engineer Dave Coleman explained that it is Mazda's approach to development that will allow it to bring the engines from mythology into reality.

“The whole SkyActiv strategy starts with figuring out what’s the ideal thing it is you want to do and working backward from that rather than working with what we have now and making it better,” he said.

“There is a three step plan to go from the SkyActiv engines we have now to the SkyActiv II which should lead as far as these did over the previous ones to an adiabatic engine.

“We know what we want to do and how we want to accomplish those things but none of those are affordable right now, but conceptually we know what we are going to do. That is why our cars took such a big leap from the smiley-faced ones to the SkyActiv series.” While Mr Coleman said that the adiabatic prototype was still too far off to predict when it might turn the first Mazda wheel, he said that its SkyActiv II predecessors were already well into development, which would bring their own set of advances.

“I don’t honestly know enough about what’s happening that far out to know for sure, but the stuff they are doing with the SkyActiv II five years ago was as unlikely as the adiabatic engine, and now I know it’s working. If I was having to put money on it, yeah we’ll pull it off.

“That idea is still two generations out. We are working on figuring that out. The next-generation engine is deep in development.” The first adiabatic engine could use either spark or compression ignition, but before that, a delayed SkyActiv II diesel is likely to roll out as a stepping stone, bringing fuel efficiency and torque gains to the company's first-generation SkyActiv oil-burner.

Mr Coleman said that Mazda had been gearing up to launch the diesel successor in 2014 but the determination of development engineers to not rely on diesel exhaust fluid (AdBlue) had delayed the introduction.

“We were supposed to launch it a couple of years ago and that’s why we started doing all our motorsports around it and we were really sure that we could make it pass emissions regulations without urea injecting, and we did, but we couldn’ t get it to drive well and pass emissions.” While the development team has made more progress in the meantime, Mr Coleman explained that the constantly changing emissions standards, and recent Volkswagen diesel emissions scandal had moved the goalposts.

“Now we’ve got one (diesel) that does both (low emissions and driveability without AdBlue), but now it is a lot harder to certify so we’re not making any promises until the EPA (US Environmental Protection Agency) tells us it’s okay because they are changing the rules all over the place. They are really bitter over the Volkswagen thing – understandably.

“We don’t know what all the hoops are going to be but once we’ve jumped through all of them then we will announce it.” While the company remains committed to ambitious targets such as the adiabatic engine, it is less convinced by more attainable technology including dual-clutch and nine-speed transmissions as adopted by many manufacturers.

“Dual clutch transmissions are overrated,” said Mr Coleman. “They can do some brilliant things but they’ve got some weak points.

The essence of a dual-clutch transmission's rapid operation is that it has the next gear already engaged on a second driveshaft and clutch, but Mr Coleman explained that transmissions with large numbers of ratios often have to shift more than one gear, which defeats the object of the DCT.

“They are doing a huge number of gears and if you’re doing that, you're also having to skip-shift a lot and dual clutches don't do that very well,” he said.

“We’re not super-hot on the nine-speed, ten-speed transmissions,” Coleman explained.

“With a nine-speed, sixth, seventh, eighth and ninth are all stacked together, and they’re all so tall that the engine can’t generate enough torque to do anything in ninth gear. So every time you move the gas pedal, there’s a downshift. You get that rubbery disconnected feel in the gas pedal.” Instead, Mr Coleman said that coupling high-torque engines with fewer ratio gearboxes was the better solution.

“Go back to how we want the throttle response to be. You can’t have that direct response if there’s a gear shift in the way. That's why the CX-9 has a six-speed – we built an engine that develops the torque at the rpm that you're already cruising at so you don't have to shift.” The CX-9 represents another significant step forward for Mazda with its foray into SkyActiv turbocharged petrol power. The large SUV touches down on Australian soil next month.

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