Porsche has awarded GKN Driveline ‘technology partner’ status after the supplier developed an eAxle for the 918 Spyder plug-in hybrid.
The electric axle module operates in full-electric and all wheel drive modes and provides a boost function.
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The eAxle combines with the sportscar’s hybrid 4.6-litre V8 powertrain. The module develops maximum power of 95kW and can deliver up to 1,500Nm of torque to the front wheels via a fixed gear ratio. A customised, compact differential engages the torque seamlessly to always ensure the car has optimum power distribution. The differential also disengages the module to minimise drag losses and maximise efficiency. At speeds above 265km/h (164mph) a clutch isolates the electric motor to prevent it from overspeed.
Porsche wanted the Spyder to have the lowest possible centre of gravity and ground clearanceso GKN positioned the output overhead using a new lubrication method to manage the oil flow.
The oil reservoir is positioned above, not below, the geartrain. Oil is gravity fed down onto the bearings and gears until it reaches the high speed input at the bottom where it is then circulated back to the oil reservoir at the top. This minimises the amount of oil on the input shaft, keeping churning losses to a minimum. To ensure the critical areas remain lubricated even in disconnect mode, the motor is driven for brief, intermittent intervals to maintain a constant flow of oil.
The Spyder’s tight packaging also means there is almost no air flow around the transmission and so water cooling was needed to manage the heat generated by the module’s high power density.
