Volvo reveals 'triple-boost' 336kW four-pot

Not content with producing a V8-rivalling 298kW twin-charged plug-in hybrid system for its range-topping new XC90 T8, Volvo Cars has now revealed a "triple charged" version of its 2.0-litre four-cylinder Drive-E petrol engine that stumps up a feisty 450hp (336kW).

No torque figure has been announced and it's not clear if the 'High Performance Drive-E Powertrain Concept' will reach production, let alone what vehicle it might power.

But the convincing demonstration of the Scandinavian brand's downsizing engine strategy provides a tantalising taste of what could come from Volvo's next Polestar-tuned high-performance models – likely to be the XC60 and V40.

As we've reported, Volvo has been busily working on high-output versions of its new 2.0-litre Drive-E powertrains with performance partner Polestar and this 336kW version is the unequivocal result.

Easily eclipsing Volvo's hottest production engine to date, the T6-based 257kW 3.0-litre turbo-six from the S60 and new V60 Polestar models, the new force-fed four also out-powers the benchmark 265kW/450Nm outputs of the 2.0-litre turbo-petrol engine seen the Mercedes-Benz A, CLA and GLA 45 AMGs.

The hottest production Drive-E engine seen so far will also out-power the range-topping XC90 T8 Twin Engine, which will follow the May 2015 local launch of garden-variety versions of Volvo's new SUV flagship in the third-quarter of next year, when it lands here with a $122,950 pricetag.

Combined with a 60kW electric motor driving the rear wheels, the supercharged and turbocharged 239kW 2.0-litre petrol engine brings the XC90 PHEV's total outputs to a V8-like 298kW and 640Nm.

Performance and fuel economy figures have not been divulged, but with a 40km all-electric driving range, the T8 is claimed to be "the world's most powerful and cleanest SUV".

From launch, the new XC90 will be available with turbocharged D5 diesel and T6 petrol engines, but of course the Drive-E concept engine also blows these engines away.

How laggy or peaky the high-output turbo-four is in the real world remains unknown, but as Polestar Technical Project Manager Henrik Fries told motoring.com.au in Sweden in August: “There is no problem having over 600hp [450kW, from four cylinders] but what you end up with is a very ‘edgy’ engine.

"The big challenge is how we deliver [the power] and deal with drivability.”

Volvo now claims to have solved these issues, with an unusual 'triple-boost arrangement in which the 2.0-litre inline four incorporates two parallel turbochargers fed by an electrically powered turbo-compressor.

BMW has employed three turbochargers on its straight-six diesel engine, but in the case of Volvo's triple-turbo petrol four, rather than being fed to the cylinders, the compressed air from the third e-turbo is used to spool up the pair of parallel turbos. Fuel is fed by a dual fuel pump working at 250-bar pressure.

"With this kind of power density, this triple-boost installation and unique fuel system enables a very dynamic drivability without any turbo lag, compared to a mono-turbo," says Volvo.

"There are several high-power small-size applications where one large turbo is used to create a high level of power available from other manufacturers, but the driving experience suffers due to slow engine response," said Volvo Car Group's Vice President of Powertrain Engineering, Michael Fleiss.

"We felt that with our heritage of being among the first car companies to embrace and offer a broad range of turbo technology since 1981, that we could improve this."

Apart from Volvo Polestar Racing, the High Performance Drive-E Powertrain Concept was also developed with early input from Volvo suppliers AVL and Denso.

"This was a very exciting project as we pioneered a combination of technologies in the same application, and the result is a quite unique engine with its high power yet quick response," said Mattias Evensson, Race Engine Director at Volvo Polestar Racing.

"Above all, its compact size improves weight distribution between the front and rear axle and lowers the centre of gravity -- two factors that have a significant effect on the handling, whether it is a race car or a street car."

Volvo has not revealed fuel consumption or CO2 emissions figures for its super-four, but says its wildest ever four-cylinder engine 2.0-litre engine the downsized hot four "demonstrates this ambition and the versatility" of its new 2.0-litre Drive-E powertrain family.

"When we launched the Drive-E powertrain family, our aim was to deliver the most advanced four-cylinder engines in the industry based on emissions and fuel consumption relative to performance and drivability," said Volvo Car Group's Senior Vice President for Research and Development, Dr Peter Mertens,

"It may sound odd, but this 450hp engine is part of this work. Down-sizing must offer customers attractive and usable power for broad scale emissions reduction to work. Compact powertrains free up space and weight in the structure of the car, which can be used for electrification and even further emissions reduction. And that is our ultimate ambition," said Dr Mertens.