Volvo has finally revealed the full details of the high-tech T8 powertrain that will power the plug-in hybrid version of its XC90 SUV. The XC90 T8 combines an electric motor with Volvo's supercharged and turbocharged Drive-E four cylinder engine, for a hybrid system that can run in electric-only mode for zero-emissions driving or combined with the ICE for increased power.

The four-cylinder Drive-E petrol engine beneath the XC90 T8's hood produces 318 hp (237 kW) and 400 Nm (295 ft lb) of torque on its own, and powers the front wheels. Volvo claims the Drive-E produces as much power as engines twice its size, thanks to the supercharger and turbocharger that bolster its outputs.

Providing electric power is a high voltage (270-400 V) battery that produces 65 kW (87 hp), and is centrally-mounted in a tunnel that runs down the middle of the car's chassis. Volvo claims this position doesn't impact on interior space, allowing the XC90 T8 to seat seven people with space for their luggage. The battery is hooked up to the XC90's electric motor, which is able to deliver 60 kW (82 hp) to the rear wheels, either on its own or in tandem with the petrol engine working up front.

In between the the XC90 T8's engine and transmission, Volvo has fitted the car with a crankshaft mounted starter-generator (CISG), which allows the petrol and electric motors to work seamlessly behind the scenes. As well as acting as a starter motor, the 34 kW unit can provide an extra 150 Nm (11 ft lb) of torque when combined with the petrol engine.

To maximize the battery's charge, the new XC90 T8 is fitted with regenerative braking, allowing it to harvest energy when drivers lift off the throttle. The amount of energy that is actually regenerated is controlled by a stability function to stop the car slowing too aggressively when you lift off the throttle, and to stop the way the brake pedal responds from feeling unnatural.

Keeping all this electric hardware cool is a challenge that Volvo has attacked by fitting the XC90 T8 with a two-circuit system. The first circuit cools the CISG and electric motor, while the second keeps the battery cool both passively and, if necessary, actively by using the car's climate control system.

This complicated combination of electric and petrol power allows drivers to use their car in five separate modes. As you'd expect, Pure electric mode uses only the rear-mounted motor to power the car, and Volvo claims that a range of over 40 km (25 mi) is achievable. Moving into Power mode, which can take the car from 0 to 100km/h in 5.9 seconds, combines the instant response of the electric motor with the petrol engine's more powerful top end performance for, according to Volvo, power and response to rival a V8.

Manually selecting all-wheel drive (AWD) mode also takes advantage of both motors, to provide more traction for drivers on demand, while Save mode allows drivers to hold the battery's charge for later use. Finally, the engine defaults to Hybrid mode, where the car will automatically alternate between petrol and electric power for maximum fuel efficiency. This complex combination of systems allow the T8 to emit just 59 g/km on the New European Drive Cycle (NEDC) with fuel economy of 2.5 L/100km, and a U.S. driving cycle fuel economy figure of 59 MPGe.

Source: Volvo

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