No four for Porsche 911

Technology developed for Porsche's all-new 9A2 six-cylinder turbocharged boxer engine that has just debuted in the latest 991.2 911 Carrera will be used in the four-cylinder boxers to debut in the 981.2 Boxster and Cayman in 2016.

But the four-cylinder won't be trekking back up into the 911 range, which will remain avowedly six-cylinder.

"Not as long as I am the boss of the 911 there will be no four cylinder engine in the 911," long time 911 development chief August Achleitner declared.

"It is not necessary."

Base models of the 981.2 versions of the Boxster drop-top and the Cayman coupe are tipped to be powered by a 2.0-litre turbocharged boxer four-cylinder, while the S and GTS will upgrade to a 2.5. None of this has as yet been confirmed by Porsche.

But Achleitner went as close as he could to confirming that technology in the engine such as the cylinder head design, which now features central rather than side injection and exhaust cam variable valve timing, would transit to the fours.

"Maybe we take something from this for small engines," he told motoring.com.au at a 991.2 Carrera technical workshop prior to the car's debut at the Frankfurt motor show this week.

"You can imagine if we develop a new engine today we talk about engine families because the most complicated thing in developing a new engine is to get the best fuel consumption data in combination with emissions.

"This is very dependent on the layout of the combustion chamber itself and the intake system and so on - the position of the injector and the plug. It is very dependent on very small details.

"So in the best way the company can do – as every company does – you take the layout of this cylinder head in detail for each cylinder and take it over to other engines because then you know it works."

Achleitner's position was echoed by boxer engine development manager Thomas Brindle.

"We don't do all this for just one engine group, for one derivative," he said.

Achleitner insisted not even a forthcoming 911 hybrid would use a four-cylinder internal combustion engine, even though such a move had been rumoured as being under consideration.

"Of course we are thinking about hybrid versions and let me say evaluating how good a hybrid version would work in a 911 ... not today, but maybe in the next generation or so on.

"So we do a lot of pre-development work, but as well also these versions not with a four cylinder."

Achleitner said the 3.0-litre six-cylinder 9A2 worked for the 911 because it meant there was still plenty of initial power on tap to negate any initial lag before the twin turbochargers spooled up.

A smaller engine such as a 2.0-litre would not have the same response, he suggested.

"If you take the turbochargers away the 3.0-litre is not a really small engine. It has not been a problem.

 "[In a 2.0-litre] the combustion engine itself does not produce so many exhaust gases to accelerate the turbocharger in time."