Porsche 718 Cayman GT4 & 718 Spyder: naturally aspirated

J-C Etter

6 years ago

A good surprise for fans of pure driving pleasure.

Porsche masters the art of range segmentation and applies its recipe universally: a base model, an S version, a Turbo and a GTS. All offer a subtle nuance in the driving experience. But there is a segment which Porsche cultivates with even more care: GT cars. These are the purest developments, the most coveted by enthusiasts, those where comfort and practicality or even economical considerations give way to performance and the quest for ultimate driving pleasure. This is what sets apart the 911 GT2 RS, GT3 RS, GT3, Speedster and also the Cayman GT4 and Boxster Spyder.

With the 718 Cayman GT4 and 718 Spyder, Porsche presents the second iteration of the latter two. Their chassis builds on the 991.2 GT3, with a redesigned rear axle adapted to the mid engine layout. Rear wheel steering was not transferred over.

The aero package has been refined. A new diffuser has been designed to work in conjunction with the new rear wing and the undertray. This results in a 50% increase of downforce without affecting drag. The diffuser contributes 30%, the wing 20%.

The wing angle can be adjusted between 0 and 4 degrees, this last setting being designed for track use. When selected, ducts underneath the front wing need to be opened to maintain proper balance. Air curtains are integrated in the front section to calm the air flow along the front wheels.

The engine should be a treat. Porsche has developed a specific naturally aspirated 4 liter high-revving flat-six which puts out 420 hp at 7600 rpm, with 420 Nm of peak torque being maintained between 5000 and 6800 rpm, and the limiter kicking in at 8000 rpm. This engine is a derivative of the 992 Carrera S unit, but without the twin turbochargers.

	718 GT4	981 GT4
Engine	Flat 6 3996 cm3	Flat 6 3800 cm3
Power	420 / 7600	385 / 7400
Torque	420 / 5000-6800	420 / 4750-6000
0-100 km/h	4.4	4.4
Top speed	304	295

Bore (102 mm) and stroke (81.5 mm) are identical to the engine which powers the GT3 and GT3 RS. The new engine integrates the same piezoelectric injectors used on the 992 Carrera S and particle filters to comply with applicable regulations.

Markus Atz, project leader for the 718 GT4 and Fabian Zink, powertrain lead for the 718 are very proud of their achievements. They explain that complying with Euro 6d standards was particularly challenging.

Porsche thinks it is essential to preserve naturally aspirated engines for this model line, a statement which bodes well for the upcoming 992 GT3: Porsche has the technology to continue to market high revving engines for its GT cars. Cost constraints however made it impossible to use a derivative of the 991 GT3 4 liter block. Beside economic aspects, the GT3 unit has not been designed for a mid engine configuration.

Fabian Zink explains further that an instrumental element was the application of a new cylinder on demand scheme, a first on Porsche’s flat six engines. Each bank can be deactivated for up to 20 seconds in sequence while maintaining adequate thermal conditions in the particle filter and catalytic converter. This deactivation system is often activated in normal driving and contributes significantly to CO2 emissions. Zink concedes that the switch to 3 cylinder mode can be perceived through a slight alteration of engine noise and vibration.

The packaging of the rear section was the subject of a hard battle between aero and powertrain engineers. The design of an efficient diffuseur required a lot of volume where the rear muffler would ideally fit. Every cubic millimeter available had to be used to preserve sufficient volume and satisfy acoustic requirements.

The 6-ratio manual gearbox is identical to the unit used in the previous generation Cayman GT4, but a twin clutch PDK will this time be offered later as an option. Kerb weight has increased by 35 kg. Porsche has not timed a good lap on the Nürburgring Nordschleife, but expects to shave off around 10 seconds compared to the 981 GT4, thanks in part to the new high performance tires.

Some of the suspension arms are connected to the body using ball joints which provide a more precise feel. The PASM adaptive suspension lowers the body by 30 mm. The Porsche Stability Management (PSM) can be deactivated in two steps. Porsche Torque Vectoring (PTV) with mechanical rear differential lock is tuned to enhance the
longitudinal and lateral dynamics. The GT4 also comes with the option of a Clubsport package. This includes a rear steel roll bar, a hand-held fire extinguisher and a six-point seatbelt on the driver’s side.

The 718 Spyder applies this drivetrain and chassis package in the guise of a light weight roadster. An active rear wing which deploys from 120 km/h replaces the GT4’s fixed wing, resulting in a small loss in downforce compared to the GT4.

As with the 981 Spyder, soft top operation is manual: a button on the dash unlocks the aluminum tonneau cover and allows manual deployment of the soft top.

Performance is almost identical to the 718 Spyder with the same 4.4s for the 0-100 km/h acceleration and a slightly lower top speed of 301 km/h. Fuel economy according to NEDC is 10.9 L/100km for both models, or 249 g/km of CO2 emissions.

With the 718 GT4 and Spyder, Porsche caters to the niche of purist sports car fans, in particular those who could not get a 981 model. The development of a specific naturally aspirated flat six is a strong testimony to this segment and attributes that resonate with these customers.

Prices for Switzerland are however increasing significantly. The Spyder jumps from CHF 97’600 to CHF 123’400. The 718 Cayman GT4 is priced at CHF 127’200 vs CHF 104’700 for the 981 GT4. The swiss package includes the Sport Chrono pack for the Cayman GT4, bi-xenon PDLS headlights, dual zone AC, rear parking assistance satellite navigation (without Apple Car Play), DAB+ digital radio, cruise control, adaptive mirrors, tinted windshield and the warranty extension to 4 years.

In Germany, prices are set at €93,350 for the Spyder and €96,206 for the Cayman GT4.