The updated 991 generation of the Porsche 911 will make its debut at next month’s Frankfurt motor show - and for once, the changes are more than just tweaks to the exterior styling and specification.
Most notably, the 911 finally gives in to emissions legislation and switches from a normally aspirated flat-six engine to a twin-turbocharged motor.
We’ve ridden with Porsche’s development team, which has been thrashing four prototypes of the car on roads based out of Cape Town in South Africa. Our trip was actually in February, but that’s peak summer in SA, with an average daily temperature of 26.5deg C.
Judging by the exteriors of the test mules we experienced - and even taking into account the patchwork of bandages over their bodywork - it would appear that there will not be any significant changes in the 911’s styling. It’s clearly time to focus on the rear-mounted motor.
In principle, downsizing and turbocharging are the simple, quick answers to the new emissions standards that will kick in by 2020. In practice, it’s far from a simple transition - particularly when you’re trying to replace an atmo engine with thousands of development hours and countless improvements behind it. One of the existing 911’s standout characteristics is the sharp response and smooth power delivery - so the turbocharged engine has to provide more than pure grunt.
August Achleitner, the vice-president in charge of product development for the 991 series, says Porsche will not give up the exquisiteness of the normally aspirated flat six, even with the reduced engine displacement and turbocharging. He’s less forthcoming on what the engine’s capacity will be, but our guess is somewhere around 3.0 litres.
This falls in between the 2.7-litre engine of the Boxster and Cayman and the 3.4 engine of the current Carrera. Stick twin turbos on a 3.0 and you could have the required 400bhp-odd for the base model, with only a modest tweak required to produce the 20bhp hike that should come with the Carrera S. Achleitner says the target fuel economy is just over 40mpg - without any notable sacrifices in performance.
From the passenger seat, the difference between the turbocharged engine and the normally aspirated motor is mainly throttle response. This gives Porsche a potential problem, because the standard Carrera will need to have a different character from the 911 Turbo. Achleitner says Porsche did consider relocating the intercooler - attaching it to the rear engine cover instead of its traditional position in front of the rear wheelarch - but it made the air intake so complicated that efficiency became a concern.
To compensate, then, Porsche’s engineers have added a Sports Response Button (SRB). It has four options - 0, S, SI, and I - and sets corresponding throttle opening levels to enhance the engine response, while minimising the turbo lag.
For example, S is used for highway driving, and SI is for sports driving on a circuit. ‘I’ stands for individual, allowing you to configure the throttle setting to your own preference. We weren’t able to try these settings for ourselves - but it’s an interesting that Porsche has considered it a necessary solution.
In any case, we suspect that the 911 has moved on considerably since our time with it. After our miles in South Africa, the prototypes were due to head for Canada and severe cold weather. It may officially be a facelift, but this incarnation of 911 represents one of the biggest steps in the car’s history - so it’s no surprise that Porsche is taking no chances.
Yoshihiro Kimura
Read more:
2015 Porsche 911 facelift - everything you need to know
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