Porsche 718 Boxster: Full details

Porsche has announced full specifications of its upgraded 718 Boxster at a technical workshop in Marseilles this week, ahead of its world debut at the Geneva motor show in March, its global launch in April and its Australian release in June.

The specs contain a number of surprising new details about the first four-cylinder engines to power the Boxster in its 20-year lifespan – beyond the headline upgrades including 25kW more power, 100Nm more torque and 1L/100km lower fuel consumption at base level.

Although Porsche had been widely expected to power its 2016 Boxster and Boxster S with a new turbocharged 2.0-litre boxer engine in two different states of tune, the larger and more powerful 2.5-litre Boxster S engine is in fact substantially different.

Both new-generation single-turbo boxer fours share the same 76.4mm stroke and are both highly oversquare, allowing them to make peak power at 6500rpm and rev to 7500rpm.

They also share the same 9.5:1 compression ratio, which is also lower than the naturally-aspirated six-cylinder engines they replace, but still relatively high for a turbo engine.

Also in common is VarioCam Plus intake and exhaust phasing, integrated dry-sump lubrication, direct-injection, intercooling and switchable, on-demand oil and water pumps. But that's where the similarities end.

With a 91.0mm cylinder bore, the Boxster's 1988cc engine generates 220kW (300hp – up from 195kW in the old model's 2.7-litre atmo six) and 380Nm of torque over 1950-4500rpm – much lower and broader engine speeds than before.

The 2497cc Boxster S engine, meantime, employs bore dimensions of 102.0mm, essentially making it a big-bore version of the base Boxster four, and variable-geometry turbine (VGT) tech from the 911 Turbo.

Porsche claims it is the only manufacturer to use VGT technology on petrol engines and in this case the result is 257kW or a neat 350hp, plus 420Nm of torque over an even broader 1900-4500rpm.

That's 26kW more power than the 3.4-litre atmo six it replaces, along with 60Nm more torque.

With just 37kW (50hp) less power and 40Nm less torque, the Boxster engine actually has a higher specific output than the Boxster S – 111kW/litre versus 103kW/litre.

Despite its engine weighing 8kg less, the base Boxster manual is 5kg heavier than before at just 1335kg, and 20kg lighter than the 718 Boxster at 1355kg, with PDK adding 30kg to both.

Of course the Boxster S still has a better weight-to-power ratio (3.9 v 4.5kg/hp), as well as the higher top speed – 285km/h v 275km/h for both six-speed manual and seven-speed auto models.

Naturally, the 718 Boxster S is quicker than before too, hitting 100km/h in a claimed 4.2 seconds in PDK form with optional Sport+ mode – 4.4 without and 4.6 as a manual.

The standard Boxster is slower to 100km/h in all forms: 5.1 seconds for the manual, 4.9 for the PDK and 4.7 for the PDK with Sport+ – 0.8 seconds quicker than before.

The downsized turbo engines don't just make the 718 Boxsters quicker and faster, but up to 13 per cent more efficient. However, all performance and fuel consumption figures are based on recommended 98 RON super-premium unleaded petrol.

The most efficient Boxster (2.0, PDK) is rated at 6.9L/100 km – down 1.0L/100km on its 2.7-litre predecessor – while the 2.5-litre Boxster S turbo consumes 7.3L/100km – down 0.9L/100km from the 3.4-litre six it replaces.

CO2 emissions from the Euro 6-compliant engines are as low as 158g/km for the Boxster PDK (168g/km manual), rising to 167 and 184g/km for the Boxster S.

Also aiding the base Boxster's efficiency are slightly slipperier aerodynamics, with a 0.32Cd drag coefficient (0.32 for the S). The Boxster also has a 10-litre smaller fuel tank, at 54 litres.

While the base 718 Boxster rides on 18x8.0-inch front wheels with 235/35 tyres and 18x9.50inch rears with 265/45 rubber, the Boxster S ups that to same-width 19-inch front wheels with 235/45 tyres, and wider 19x10-inch rears with 265/40 tyres, resulting in an 8mm-wider rear wheel track of 1540mm.

The Boxster S wheels are newly designed and 20-inch wheels will be an option.

Other differentiators for the Boxster S include dual exhaust outlets and thicker front brake rotors – though both Boxsters run 330mm front and 299mm rear vented and cross-drilled discs gripped by four-piston fixed aluminium monoblock callipers at both ends.

Porsche says both cars' electromechanical steering system is now 10 per cent more direct as standard, while the latest 911's new steering wheel-mounted Sport Response Button comes in PDK models optioned with the Sport Chrono Package, which now comprises Individual as well as Normal, Sport and Sport Plus modes.

As we've reported, although it's hard to tell, Porsche says the 718 Boxster's exterior design is all-new, except for the bonnet lid, windscreen and soft-top, while the cabin and dashboard are also revised.

Both models get the latest Apple CarPlay-equipped Porsche Communication Management (PCM) touch-screen infotainment system.

As standard, all Australian Boxsters will come with bi-xenon headlights with integrated four-point LED daytime running lights and Porsche Dynamic Light System (PDLS), plus auto-dimming mirrors, digital radio, mobile phone preparation, audio interfaces, navigation, voice control and 110W Sound Package Plus.

The Porsche Active Sport Suspension (PASM) option lowers the Boxster and Boxster S by 10 and 20mm respectively.

Replacing 981, the 982-series Boxster wears a 718 badge to draw a link with the mid-engined four-cylinder boxer-powered 718 sports cars that won numerous races in the 1950s and 1960s, among them the legendary Targa Florio and Le Mans.