Overview: Peugeot 508 RXH

The 508 RXH is the most powerful and upmarket car so far to use PSA’s Hybrid 4 system. This, perforce, means that it has a conventional (diesel) engine in the nose driving the front wheels and a separate — but electronically integrated — electric drivetrain in the tail. As a series-parallel hybrid it can be driven by either or both of the drivetrains, which means that it can be front-, rear- or four-wheel drive.

The RXH is available only as an estate and is intended to compete with existing up-market all-road vehicles from the likes of Volvo and BMW. Equipment worth mentioning includes a head-up display (including navigation system information), a panoramic glass roof and dark-tinted acoustic laminated side windows. A locking system called ‘Open and go’ minimises (in fact obviates) the need for the key to be used mechanically, operating passively in detecting the presence of the key close by or inside the car. Main beam headlamp assistance is standard, as are an automatic electric parking brake, new telematics, Peugeot’s Connect SOS and Assistance and Xenon lights.

The main power-unit is PSA’s two-litre DW10 163PS and 340Nm. With the electric motor working in parallel, the total system output — albeit briefly — is 200PS and 450Nm. In the usual way, the hybrid controller balances the two power-units according to driving conditions and the state of charge of the battery-pack. In this case, because of the unusual drivetrain(s), traction also becomes a factor in distributing drive. Over the NEDC rolling-road combined cycle, the RXH delivers 67.2mpg, with CO2 emissions of 109g/km.


Clearly there is a vast difference between the TXH and a ‘lesser’ 508 estate, even one with the same diesel engine. Track increases by 40mm, while ride-height goes up by 50mm. Styling changes include an extension to the grille on its lower edge.

Inside, the gear selector lever has a design that combines the functions and ergonomics of a conventional gear selector lever with a computer mouse called the ’manettino’. The load area is fitted with aluminium rails and four ‘solid chrome‘ (stainless steel, presumably) load-securing hooks. The tailgate is motorised; there’s 11l of storage under the floor, but no spare wheel. We would rather have the wheel.

Quad-zone air-conditioning is fitted, and the driver’s seat has electric lumbar massage — we sincerely hope this extraordinary gimmick is worth its weight and expense, as we’ve seen often enough that a basic but well-designed seat can show up ‘sophisticated’, electrically-adjustable lumbar support as just a variable lump. By way of a more down-to-earth feature, the cushion edges of the front seats are electrically adjustable.

The RXH’s running-gear consists of a pseudo-McPherson arrangement at the front and PSA’s Hybrid 4 rear sub-assembly, which carries a multi-link rear suspension set-up along with the complete electric drivetrain.

There are four drive modes available in this version of Hybrid 4: Zero Emission Vehicle, 4WD, Sport, and Auto. In all modes, battery-charging is carried out automatically, both by the engine and on the overrun using the car’s kinetic energy.

During acceleration, both the diesel engine and the electric motor work together. In Sport mode, there is a ‘boost’ function that maximises drive torque for a brief squirt of acceleration. Normally, total system torque is limited to 450Nm — enough for most purposes, we would think — though Peugeot hints that outputs up to 500Nm might be available briefly at higher road speeds. The maximum combined system power can reach 200PS, by combining the 163PS from the diesel with the ‘on-demand’ maximum output of 37PS from the electric motor. The HDi delivers up to 300Nm to the front wheels, while the electric motor can supply a maximum of 200Nm to the rear wheel.

The 508 RXH is built at Rennes, with the modular hybrid rear drive sub-assembly originating from Mulhouse. Sales in the U.K. should start in spring 2012.

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