Porsche 911 Turbo & Turbo S : 991 Technical Guide

The new $359,800 Porsche 911 Turbo and $441,300 911 Turbo S boast more power, better acceleration, a wider track, overboost function for more torque, an electro-hydraulically controlled multi-plate clutch and water-cooled front-axle, active rear-axle steering, a new torque vectoring system, dynamic engine mounts and chassis control, bigger wheels, larger brakes, active aerodynamics with the world’s first variable front spoiler and a very suave interior.

Engine and Transmission

Starting at the heart, the new 2014 Porsche 911 Turbo and Turbo S (model designation 991) are powered by the same turbocharged 3.8-litre six-cylinder engine as the 997 models, but now with 383kW (up 15kW) and 660Nm (up 10Nm) in the Turbo, and 412kW (up 22kW) and 710Nm (up 10Nm) in the Turbo S.

Both engines use two turbochargers with variable turbine geometry, making them the only road cars with such a setup.

Porsche says the extra power and torque comes from better engine efficiency with higher combustion pressures as well as new valve timing and ignition angle tuning. In the Turbo S, the charge pressure has been increased to 1.2 bar while max engine speed has gone up by 200rpm to 7200rpm.

Tick the box for the Sport Chrono package and you get the overboost function which increases maximum turbocharger pressure by around 0.15 bar for up to 20 seconds (when the accelerator is flat to the floor), allowing torque to increase to 710Nm for the Turbo and a whopping 750Nm for the Turbo S.

The Porsche 911 Turbo will do the 0-100km/h dash in 3.4 seconds, and this is reduced to 3.2sec on overboost, making the 991 911 Turbo faster to 100km/h than the 997 911 Turbo S. It hits 200km/h from rest in 11.1 seconds or 10.8 seconds on overboost, and tops out at 315km/h.

The new 911 Turbo S accelerates from 0-100km/h in 3.1 seconds, heading to 200km/h in 10.3 seconds and on to a top speed of 318km/h.

Though largely irrelevant for Porsche 911 Turbo and Turbo S buyers, fuel consumption falls 16 per cent, both down to 9.7 litres of premium per 100km on the combined cycle.

The economy figures have been helped by the company’s updated gearbox (PDK) which now shuts the engine off while coasting to a stop or disengages the clutches during a coasting phase (e.g. down a hill) to save fuel. Interestingly, the gearbox supplements the seven driving gears by adding virtual intermediate gears.

Porsche says the virtual gears are used to reduce engine speed during an undisturbed, constant-speed mode of driving (such as when cruise control is engaged) when the gear up would reduce engine revs below the specified lower speed limit. This works when the transmission controller engages adjacent gear levels and controls the two clutches for defined slip in transferring the drive power.

Like most dual-clutch transmissions from the Volkswagen Group, Porsche’s PDK sits its clutches in an oil-bath, which should result in nearly wear-free usage.

The brakes on the Turbo now measure 380mm while the Turbo S gets Porsche Ceramic Composite Brakes measuring 410mm at the front and 390mm at the rear.

Aerodynamics, chassis and dimensions.

The new 2014 Porsche 911 Turbo and Turbo S are the widest of their kind yet. The front track of the Turbo measures 1541 mm (up 51mm) while the rear has grown 42mm to 1590 mm.

The 991 model also employes active aerodynamics, with the world’s first variable front spoiler that operates using pneumatic actuators. The front spoiler is soft and can take a reasonable beating, and can extend both at the sides and at the front to improve downforce.

The rear spoiler, too, can extend upwards by 25mm or 75mm. The wing deploys at 120km/h (or manually) and retracts when speed drops below 80km/h.

At 300km/h and with the front and rear aero aids in full force, there’s an additional 44kg of downforce at the front and 88kg at the rear.

One of the new features of the 911 Turbo and Turbo S is the active rear-axle steering. Though available in one form or another in many cars for the past few decades, the Turbo’s application varies slightly.

At speeds of up to approximately 50 km/h the two electromechanical actuators can turn the rear wheels in the opposite direction of the fronts by up to 2.8 degrees, which reduces the turning circle by 0.6m to a claimed class-leading 10.6m.

Go past 80km/h and it will do the opposite, turning the rear wheels up to 1.5 degrees in the same direction as front wheels, allowing for better cornering and manoeuvrability at high speeds.

Porsche says the active rear steering helped it achieve the impressive 7:27 lap time around the Nurburgring Nordschleife track in Germany.

The Porsche Torque Vectoring Plus system further enhances the rear steering by using automatic braking on the inner wheel around corners to add a natural turning impulse in the correct direction.

If you forked out the extra cash for the Turbo S you get the dynamic engine mounts that loosen and stiffen depending on driving conditions and the Porsche Dynamic Chassis Control (PDCC), which essentially keeps the 911 from having much body roll in and out of corners.

The PDCC mainly decouples the stabiliser in straight-line driving and puts in effect opposing suspension spring deflections on uneven roadways. Porsche says this helps the 911 Turbo S improve its transverse acceleration and handling, which in turn reduces the roll angles and increases the possible speed through corners.