The Volvo XC90 T8 "Twin Engine" plug-in hybrid SUV is now the most powerful production Volvo ever, thanks to tweaks from in-house tuner Polestar.
Polestar started out as an independent race team and Volvo tuner, and was bought outright by the Swedish carmaker last year.
Over the years, it's offered everything from parts to dedicated performance models like the current S60 Polestar and V60 Polestar.
In addition, it now offers "Polestar Performance Optimization" tuning packages, which increase performance while maintaining the factory warranty.
It was one of these packages that turned the XC90 T8 plug-in hybrid into Volvo's most powerful production model.
With the Polestar upgrades, the T8 produces a combined 421 horsepower and 501 pound-feet of torque in hybrid mode.
The extra power will get the XC90 from 0 to 62 mph in 5.5 seconds, Volvo says.
The powertrain remains mechanically unchanged, with a 2.0-liter turbocharged and supercharged four-cylinder gasoline engine and eight-speed automatic transmission working with an electric motor to drive all four wheels.
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Besides unlocking more power, Volvo says the Polestar tweaks—which may be primarily software related—also improve throttle response.
The XC90 T8 version of the package also introduces a new gearshift-hold feature.
This prevents the transmission from shifting while cornering, which can upset a car's balance.
Those two models share the XC90's Scalable Product Architecture (SPA) platform, and the T8 "Twin Engine" powertrain.
Polestar has already confirmed performance upgrades for some versions of the S90 and V90, but not the plug-in hybrids.
The Polestar Performance Optimization for the XC90 T8 was announced only after packages for other XC90 models were released, so Polestar may follow a similar schedule with the S90 and V90.
That may include 600-hp versions of the S90 and V90, with powertrains based around an upgraded 2.0-liter four-cylinder engine, Volvo R&D chief Peter Mertens told Motor Trend last week.
In the meantime, the Polestar Performance Optimization package for the XC90 T8 "Twin Engine" will be available for order in October.