2012 All-New Porsche Carrera: The DriveTrain is even Smarter (Part 2/12)


PORSCHE Europe: Official Press Release


The new Porsche 911 Carrera

Downsized Boxer Engine and the World’s First Seven-Speed Manual Transmission

The 911 Carrera sets the standard among premium sports cars for efficient performance. But it gets better: The new generation is even more differentiated from the competition. Porsche Intelligent Performance doesn’t just mean reducing fuel consumption but doing so while increasing power output at the same time. Courtesy of enhancements within the engine itself, accompanied by the new functions thermal management, on-board electrical system recuperation and auto start/stop function, the new models are up to 16 per cent more economical and up to 15 hp (11 kW) more powerful.

The previous engines and transmissions were an outstanding starting point for these efficiency-raising concepts. Porsche’s first venture into downsizing within a model range was the flat-six engine in the Carrera, reducing the piston stroke by four millimetres (0.16 inch) with the total displacement falling from 3.6 to 3.4 litres. The dimensions of the 3.8-litre engine in the Carrera S remained unchanged. Direct injection in both engines is now provided by multi-hole injectors, which further optimise smooth running and power by improving mixture formation. All in all, the 911 Carrera engines’ design clearly exhibits elements of the successful motor racing formula of increasing power through higher revs:

911 Carrera
new
before
Power hp
at rpm
350
7,400
345
6,500
Torque Nm 
at rpm
390
5,600
390
4,400

911 Carrera S
new
before
Power hp
at rpm
400
7,400
385
6,500
Torque Nm
at rpm 
440
5,600
420
4,400

Potential savings 0,2 l/100 km: Thermal management system

The cooling of the engine and transmission is being controlled for the first time in the new 911 Carrera by a common thermal management system. The aim: to bring all components quickly to their most efficient, stable operating temperature and ensure greater comfort for the occupants by rapid and adequate heating of the passenger compartment on cold days. Accordingly, thermal management exists to distribute heat between combustion engine, transmission and vehicle interior.

On the one hand, incorporating the transmission into the cooling circuit through the heat exchanger enables the transmission to be heated as required, thus saving fuel, while also enabling optimal cooling under maximum load. The thermal management system in the new 911 Carrera models reduces fuel consumption based on the NEDC by 0.2 litres per 100 kilometres.

Potential savings 0.15 l/100 km: On-board electrical system recuperation

In the new 911 Carrera, the on-board electrical system also helps to save fuel – by recovering kinetic energy, known as recuperation. This entails a proportion of the kinetic energy being converted into electrical energy and stored in the starter battery when the vehicle is decelerating. This is achieved by using the generator controller to increase generator power in a controlled manner during braking. This has the effect of applying a higher braking torque through the belt drive to the combustion engine’s crank shaft, slowing the vehicle and thereby reinforcing the conventional braking system.

If on the other hand the driver accelerates, the power required by the generator can be reduced, which is directly reflected in lower fuel consumption. An intelligent algorithm in the energy management system analyses various inputs from the components involved, thereby actively coordinating each recuperation process depending on the battery charge state and what the driver wants. To exploit this potential, Porsche is employing a new Absorbent Glass Mat (AGM) starter battery, which satisfies the more stringent cyclic stability and battery life requirements. On the NEDC, on-board electrical system recuperation lowers fuel consumption by 0.15 l/100 km.

Potential savings of up to 0.6 l/100 km: auto start/stop function

To improve fuel consumption and comfort, all 911 Carreras offer their drivers the auto start/stop function as standard and, for the first time, it is available for models with manual transmission as well. While the vehicle is stationary, it turns the combustion engine off under defined circumstances. This prevents the engine from idling unnecessarily while the driver is waiting at traffic lights, for example; fuel consumption and emissions are cut, especially in urban traffic.

The auto start/stop function can be deactivated or activated by pressing a button in the centre console – together with the sailing function with the PDK. The function is available as soon as the engine and transmission have reached their operating temperature. In the case of the manual seven-speed transmission, the engine switches off if neutral is selected when the vehicle is stationary and the foot is taken off the clutch. The engine restarts as soon as the clutch is engaged and a gear selected. The procedure with the Doppelkupplungsgetriebe (PDK) is different: if the vehicle brakes to a halt and the brake pedal is kept depressed, the auto start/stop function turns the engine off after approximately one second. This is signalled to the driver by the green auto start/stop symbol in the instrument cluster. The gear selector can remain in position D or M. The engine remains off even if there is a gear change to P and N.

Potential savings up to 1.0 l/100 km in everyday driving: Sailing

The new 911 Carrera is the first sports car to be able to sail. Together with the optional PDK, the driver can enjoy the fuel consumption benefits of this function, which already delivers fuel economies in the Porsche hybrid models. In a sports car, the term “sailing” also referred to as “coasting” describes the operation of the vehicle with the engine disengaged, for example on a slight downhill gradient, where the engine is idling, thus ensuring that auxiliaries such as the generator, water pump and air-conditioning compressor continue to function.

Even with the engine still running, sailing helps to save more fuel than in overrun mode. During sailing, the vehicle’s kinetic energy is applied directly to overcome driving resistance. Although no fuel is consumed when on the overrun with fuel cut-off, the vehicle experiences significant deceleration. If deceleration is not wanted, the distance that has been lost is to be covered by using additional fuel.

The sailing mode is activated if no propulsion is required or if the driver is only moderately braking all the time. The engine is re-engaged when the driver accelerates or makes demands on the engine’s braking torque by heavier braking or else by changing down manually. Sailing can also be activated manually by performing a one-touch upshift when in the highest possible gear for the relevant speed.


2012 All-New Porsche Carrera: The DriveTrain is even Smarter (Part 2/12)




2012 All-New Porsche 911 (991) in Detail:







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