Overview: Porsche 911 Carrera GTS

The new 911 Carrera GTS is the most powerful of the rear-wheel drive Carreras. It uses an uprated power-unit and, to cope with the additional performance, it adopts the wider track and wider body of the Carrera 4 models, resulting in a slight worsening of the drag coefficient from Cd 0.29 to Cd 0.30 on cars with manual transmission. As usual, the body is a hot-galvanised steel monocoque.

Porsche 911 engines are all-alloy four-cam flat sixes with liquid cooling and (perforce) dry-sump lubrication. As befits a high-performance engine, the lubricant capacity is a substantial 10l. There are two three-way catalytic converters per cylinder bank, each with two oxygen sensors.

The power-unit used in the new GTS is a derivative of the 3.8-litre engine fitted in the Carrera S. Existing features carried over include a high 12.5:1 compression ratio, direct fuelling, and Porsche’s VarioCam Plus, which provides adjustment to timing and valve lift on the intake side. There is no adjustment for the exhaust camshaft.

For the Carrera GTS, the intake tracts have been reworked to improve top-end breathing. The result is an extra 23PS, but at much higher revs — 408PS at 7300rpm against 386PS at 6500rpm. The red line on the new engine is set at 7500rpm.

But the new intake system not only improves top-end power: the torque curve is fatter in the lower and medium engine speed range, with 320Nm available at 1500rpm, a gain of sround six per cent. The maximum torque figure of 420Nm is unchanged, but is now delivered between 4200rpm and 5600rpm against 4400rpm for the Carrera S.

Although driveability has improved, ultimate performance shows relatively marginal gains. The Carrera GTS offers a 2mph increase in maximum speed — to 190mph — for a car fitted with Porsche’s six-speed manual gearbox. (There is no gain in maximum speed for cars with the PDK dual-clutch box, as their drag coefficient is marginally worse — the transmission demands more cooling air.) It’s the PDK derivatives that offer the best gain in flat-out acceleration: in combination with the Sport Chrono Package Plus, the GTS will reach 100km/h in 4.2s, one tenth of a second ahead of the Carrera S.

Over the New European Driving Cycle rolling road tests, the Carrera GTS shows no worsening of fuel consumption compared with its less powerful sibling.

Variable intake system

Much of the gain in efficiency achieved by the GTS engine are down to the use of a variable-resonance intake system. The basis of this is straightforward: the resonant length of a pipe — such as an intake pipe in a car engine — means that there is a natural optimum crankshaft speed at which charge air is delivered most effectively to the combustion chambers. If you want to broaden the range of engine speeds over which the intake system is working well, you must somehow alter the resonant length of the intake pipes as engine speed changes. This is obviously not easy. A lot of ‘binary’ systems have been used by various manufacturers, in which two different intake régimes are available, with the engine switching between them at a predetermined crankshaft speed. These systems have historically not been refined, delivering a ‘wobble’ in the torque curve at the changeover point.

For the Carrera GTS, Porsche uses six vacuum-controlled changeover flaps in the intake tracts to switch between gas-flow modes, one favouring top-end power, the other torque. As a final refinement, the intake ports are machined.

Gearboxes

The Carrera GTS uses the classic 911 drive-train layout, with its all-alloy flat six bolted directly to the transmission forming a single structural unit and driving the rear wheels alone. It does not use the all-wheel drive system of the Carrera 4, with its electronically controlled, electromagnetically operated multi-plate clutch sending a variable amount of torque to the front wheels. The standard gearbox is Porsche’s six-speed manual transmission; the Porsche Doppel­kupplungs­getriebe (PDK) dual-clutch transmission with seven forward gears is available as an option.

The PDK offers slightly increased torque in its sports programs. Its second, third and fourth gears are a little lower than those of the six-speed manual; fifth and sixth are the same; and the dual-clutch unit additionally provides a 0.62:1 cruising ratio.

The PDK’s dynamics can be enhanced with the optional Sport Chrono Package Plus. This offers a ‘Launch Control’ function for the fastest possible acceleration from a standing start; it also provides a race circuit shifting strategy for track driving, which enables very fast gear-changes. As the Carrera is emphatically not a track-racer, this looks uncomfortably like a gimmick.

Running-gear

The front wheels are located by McPherson struts with longitudinal control arms and conical coil springs. At the back, a five-link set-up is used, with cylindrical coils.

The Carrera GTS uses the increased track width of the four-wheel drive 911s. At the front, the track has been extended by two millimetres to 1488mm; at the rear, the gain is 32mm to 1548mm. Fatter anti-roll bars are fitted, and the rear tyres are broader at 305/30 instead of 295/30. The 19-inch wheel diameter remains unchanged, though the wheels themselves are centre-mount RS Spyder items.

Porsche’s Active Suspension Management system is fitted as standard to the GTS. Two manually-selectable suspension modes are available: ‘PASM Normal’ and ‘PASM Sport’. The ‘Normal’ setting offers a more comfortable basic damping rate, though the system automatically switches to a harder rate when the driver starts to drive more energetically. The ‘Sport’ setting gives harder damping rates at more modest speeds.

Porsche also offers the PASM sports suspension for the Carrera GTS Coupé. This version of the system is aimed at sporting drivers. In comparison with the normal version, the active PASM sports suspension offers a tauter suspension setting; the suspension is also lowered by 20mm. The active sports suspension comes with a mechanically locking differential.

The braking system in the Carrera GTS consists of four-piston aluminium monobloc fixed calipers on the front and rear axles plus perforated and ventilated brake discs. The discs are of 330mm x 34mm at the front and 330mm x 28mm at the rear. The optional ceramic composite brakes feature ceramic brake discs with six-piston monobloc fixed calipers at the front and four-piston monobloc fixed calipers at the rear. The perforated and ventilated ceramic composite brake discs are of 350mm diameter and weigh around 50 per cent. less than comparable metal brake discs.

Porsche 911
Carrera GTS
911
Carrera S
Cylinders 6HO 6HO
Valves 4 4
Bore/stroke 102.0/77.5 102.0/77.5
Swept volume 3800cc 3800cc
Compression
ratio
12.5:1 12.5:1
PS/rpm 408/7300 385/6500
Nm/rpm 420/4200 420/4400
Maximum speed 190 187
0-100km/h 4.6 4.7
Urban MPG
(l/100km)
17.8
(15.9)
17.8
(15.9)
Combined MPG
(l/100km)
26.6
(10.6)
26.6
(10.6)
CO2 g/km 250 250
Emissions EU5 EU5
Transmission M6 (AM7) M6 (AM7)
Driven wheels Rear Rear
Fuel tank 67l 64l
Kerb mass * 1420 1425
PS/t 287 270
Nm/t 295 294
Length 4435 4435
Width 1852 1808
Height 1300 1300
Wheelbase 2350 2350
Track: front
Track: rear
1488
1548
1486
1516
CdxA 0.30x2.05m² † 0.29x2.01m²
* DIN. EU kerb mass = DIN + 75kg.
† Drag coefficient for manual transmission car. With dual-clutch transmission, Cd=0.31.
Porsche 911 Carrera GTS
gear ratios
M6 AM7
1
2
3
4
5
6
7
Final drive
3.91
2.32
1.56
1.28
1.08
0.88

3.44
3.91
2.29
1.65
1.30
1.08
0.88
0.62
3.44
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