How Porsche heralded the end of air-cooled
The 911 Turbo (993) marks the end and the beginning: the departure of the air-cooled boxer and the arrival of a biturbo engine.
Often the era-defining significance of certain events only becomes obvious when you look in the rear-view mirror. Did Gutenberg know that his printing press would mark the end of the Middle Ages? Was it clear to Steve Jobs back in 2007 how much the iPhone would change everything? When Porsche unveiled the new 911 Turbo in 1995, this was also a defining moment for the sports car brand.
Virtually no other model epitomises the sea change that Porsche underwent in the mid 1990s: the era of the air-cooled boxer engines, which had been so intrinsically linked to the brand, drew to a close once and for all. The turbocharged 911 from the 993 model series was virtually the engine's final, and perhaps its most exciting, iteration. At the same time, the new Turbo also marked the start of something new: biturbo technology making its way into series production. Pedants may point to a similar engine design giving the 959 an almost mythical status, but that car was built in limited numbers.
The power of the twin turbos has long since become a defining feature of the 911 family. And just like the German super sports cars of the 1980s, the 911 Turbo from the 993 model series relied on permanent all-wheel drive.
When it launched, suddenly everything changed. The new model marked an important stage of development for the turbo technology as it matured and became more useable. Thanks to the new biturbo design (replacing the previous monoturbo), the era of explosive power delivery that struck the driver like an elemental force was over – even though this 911 Turbo, with 408 PS, was faster and more powerful than any other series 911 before it.
However, unlike in the 959, Porsche dispensed with complex sequential turbocharging that used one larger and one smaller turbo connected in sequence. Instead, its successor used two KKK K16 turbines, equal in size but, crucially, comparatively compact and symmetrical – one for each cylinder bank. They also continued to generate a tremendous amount of boost, forcing the intake air through the charge-air cooler and into the combustion chambers at 0.8 bar.
However, thanks to their lower mass, Porsche was able to activate the charger blades much earlier than in the single turbo of the 964. The result was astounding: at just 2,500 rpm, 450 Nm of torque was unleashed, continuing all the way to 6,800 rpm. At the same time, the four driven wheels ensured that the power delivery could be converted into spectacular propulsion. It all meant a zero to 100 km/h time of just 4.5 seconds.
This wasn't the only ground-breaking characteristic of the 993 Turbo. It had also adopted good manners, including in respect of its emission performance: it was the first car in the world to be offered with an OBD-II system. This on-board diagnostics II system required an ultra-modern engine management system like the Bosch Motronic M5.2 and considerable development work. The cutting edge technology monitored such parameters as the metal catalysts and lambda probes, how the fuel tank ventilation with activated carbon filtering was operating, as well as the secondary air injection and the fuel system.
It all translated into a remarkable success story: in its day, the 911 Turbo (993) caused a sensation, not just as the ultimate dream sports car, but as the lowest-emission car ever. It is a car whose significance only really becomes clear from today's perspective …