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The days of the big naturally-aspirated six-cylinder engine are coming to an end, and Subaru could be the next maker to drop its largest petrol engine in favour of a smaller turbocharged unit.

That’s despite the brand touting its 3.6-litre ‘boxer’ six-cylinder – which is offered in the considerably more affordable range-topping variants of the 2015 Subaru Liberty and 2015 Subaru Outback – as forming a key part of the Australian arm’s local strategy in the coming years.

As CarAdvice has previously reported, Subaru Australia is pitching the Outback and Liberty models as alternatives to the likes of the established, but soon to depart, Holden Commodore and Ford Falcon, no to mention the Toyota Aurion.

2014-holdenvsford-evokeandfalcon-comparison-16

However, Yoichi Hori, deputy general manager of Subaru’s engineering department, spoke exclusively with CarAdvice about the prospects for the big six getting the axe in favour of a more efficient turbocharged four-cylinder powertrain – possibly with plug-in hybrid back-up.

“Our research said the six-cylinder model is decreasing in the world,” Hori said. “So that’s why probably the future, many companies take the smaller displacement with a turbocharger, or diesel, or hybrid.

“Maybe smaller displacement,” he said when asked if there could be a 2.5-litre turbocharged engine. “That’s going to be more suitable for the market.”

“In terms of the body size, a 2.0-litre with a turbocharger is enough, I think,” he said, and the case is true – there is a 2.0T version of the Outback, but it is only sold in China due to a tax issue.

MY15 Subaru Outback 3.6R

Hori said that the 3.6-litre is a trusted engine, and one of the main reasons it has been kept for the new-generation Liberty and Outback models instead of a transplanted 2.0-litre boxer four-cylinder sourced from the same engine bay as the WRX is one of cost.

“One of the biggest reasons is the maintenance costs – the turbocharger makes more higher performance, so that’s why maintenance such as the oil changing costs more than six-cylinder models,” he said.

“That’s why many people think the six-cylinder more suitable for the daily driving vehicle,” he said.

So it appears clear that the future for petrol engines will be centred around a 2.0-litre turbocharged unit for larger Subaru vehicles, and an engine of the same size fuelled by diesel will likely form a part of the company’s large-vehicle makeup, too.

MY15 Subaru Liberty 3.6R

“Most companies have two kinds of diesel engine – one for the fuel economy, a smaller displacement engine and a turbocharger; and another one is the high-power model, which is more for a high-end, more premium brand,” Hori said.

“So we can make only one engine, because we are so small company. That’s why we chose just between the small and big one,” he said of the current mill, which pumps out 110kW and 350Nm – less than many of its competitors – and achieves middle-of-the-road fuel consumption.

“We are still looking for the best engine – not only for the bigger one, but also a smaller one. So we didn’t decide yet. We still looking for the new technologies,” he said, indicating the 2.0-litre diesel will likely be adapted to run in two states of tune – one focused on more power, the other, better economy.

Rumours suggest Subaru is also working on a plug-in hybrid version of the diesel engine, but Hori gave little away on such a drivetrain being under development.




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