Next-Gen Volvo S60 Polestar First Drive
The Drive-E-est Volvo of Them All
How can a little premium car company like Volvo that has sworn off engines with more than four cylinders hope to go toe-to-toe with the Mercedes-AMGs and BMW Ms of the world? Perhaps by leveraging science and engineering, as demonstrated by this "450 BHP Concept" engine.
To develop it, Volvo enlisted the brainpower of the engineering consultancy AVL, the fuel-injection gurus at Denso, and Volvo's own in-house racing team, Polestar. Their collective goal was to smite the CLA45 AMG's impressive 355-hp/332 lb-ft 2.0-liter turbo in a similar-sized package that delivered easy low-adrenaline tractability and big-engine responsiveness along with its shrieking hair-on-fire high-rpm performance. Their novel solution: triple-charging.
Step on the gas and a Valeo Gen3 R70 electric supercharger spools up 70,000 rpm, drawing a peak power of 7 kilowatts from a 48-volt ultracapacitor pack in the trunk. (The ultracaps are topped up via the alternator and a DC-to-DC converter primarily during vehicle deceleration.) This produces some 22 psi of boost pressure, but it doesn't go directly into the intake manifold. Rather, it flows through two parallel Borg-Warner turbochargers, helping spool them up more quickly. The airflow from these two single-scroll turbos -- one fed by the two outermost cylinders, the other by the inner two -- gets combined in the intercooler before heading into the engine. The e-booster shuts down at about 3,300 engine rpm once the two turbos come online, and at their peak speed of 200,000 revs they develop 36 psi of boost.
Supplying enough direct-injected fuel to burn with all that air requires a special pump designed by Denso. It looks like a tiny V-2 engine driven by a four-lobed cam off the back end of the exhaust camshaft. The injection pressure is a lofty (for gasoline applications) 3,675 psi. The injectors are also upsized from 20cc to 25cc.
The result: 450 hp at 6,500 rpm and 369 lb-ft of torque at 6,000 rpm. Interestingly, the torque does not plateau but rather rises quickly to 310 lb-ft at 2,000 revs and then follows a straight line, increasing to 6,000 rpm before tapering off.
The Polestar folks dropped this little beastie into one of their S60s (retaining standard Polestar chassis and brake hardware) backed by an eight-speed automatic from a diesel application. The torque here is slightly beyond the stated rating for the transmission, but apparently it's within the safety margin because a dozen journalists flogged it for three hours without a hitch during a demonstration event held on a dreary, damp December morning at the company's Gothenburg handling track.
So is it a CLA45 AMG-slayer? Potentially. In this bigger car with no optimization of gearing, it's said to hit 62 mph in just under 5 seconds. That's only slightly better than our last V60 Polestar wagon's 5.0-second 0-to-60-mph time, and with that car rated at 345 hp/369 lb-ft with a six-speed automatic, it's safe to assume there's room to improve that time with further tuning. If so, the lighter AMG's 4.2-second 0-60 time should be achievable.
As it stands, the car is extremely tractable, pulling strongly from any speed with no perceptible lag. Another area that needs work is the exhaust note. The test car produces a blatty rap that's borderline annoying at idle though pretty decent at full song. Powertrain VP Michael Fleiss says there are no insurmountable challenges impeding production of the 450-hp concept engine, apart from building the business case for the engine.
So you can probably count on seeing an S60/V60 Polestar variant packing this engine within the next few years. After that, imagine pairing it with the electrification for 500-plus horsepower applications in larger vehicles (X5 M-fighting XC90 Polestar?). Better still, let's hope they mount this engine just as it is in a lighter S40 Polestar. THAT would be a sure-fire CLA45-slayer.