Technology Explained: Porsche Traction Management
Tyres aren’t the only thing that determine traction. For 25 years, Porsche has been utilising four-wheel drive in the 911, with the Porsche Traction Management system increasing in complexity in recent years to optimise power transfer.
The system operates using two differentials (one for each axle). With the transmission mounted in front of the engine, the front differential is powered by a perfectly straight propshaft from the rear differential. This ensures that power is distributed evenly.
Traction on the rear wheels is managed by PTV (Porsche Torque Vectoring). PTV is the reason Porsche no longer talks of limited-slip differentials. Torque vectoring not only transfers power from side-to-side, it also independently brakes the inside wheel to enable greater turn in.
PTV is mechanically operated unless the ‘Plus’ option is specified, in which case an infinitely variable electronically locking version is utilised.
With the rear wheels taken care of, the level of power distributed to the front axle is determined by a series of sensors measuring a range of parameters, from steering angle and throttle application to lateral and longitudinal acceleration.
This information is then used to operate the electronically controlled double-clutch system, located just behind the front differential. If the rear axle is struggling to apply all the power to the road, the electronically activated clutch is engaged more positively (taking a maximum of 100 milliseconds), transferring a greater amount of the engine’s power to the front axle.
Depending on throttle application, this system can preload, meaning that traction is always available, even before the driver needs it.