Porsche V8 Engines: A Powerful History
The fourth generation has now begun. Four decades of Porsche experience with eight-cylinder V-engines have been built into the new engines of the Panamera. Each subsequent generation was developed to bring increases in performance and drivability. From the 928, Cayenne and Panamera to the 918 Spyder, each V8-powered Porsche has sought to become the most performance-focused car in its segment.
The anniversary of the Porsche V8 happened on July 8th, where 40 years ago the first water cooled, road going V8-powered Porsche drove out of the development centre at Weissach and onto the road. It was powered by a 90-degree eight cylinder engine which, from 1977, powered the first transaxle Porsche – the 928.
The new engine was a radical departure from the flat layout so typical of Porsche, and heralded a new era of engine building. Made almost entirely of aluminium – including the cylinder linings – it displaced 4.5-litres and, thanks to a low compression ratio of 8.5:1, could run on low-grade 91 octane fuel commonly found in the USA. This did, however, limit performance, with the engine producing 240hp at 5,500rpm, giving the 928 a modest top speed of 143mph. Subsequent development saw the engine grow to 4.7-litres, and with increased compression and fuel injection, it developed 310hp.
Porsche engineers played their next trump in 1986. Over the course of introducing catalytic converter technology, the eight-cylinder engine got its biggest redesign. The new CAT version had completely redeveloped cylinder heads with four valves per cylinder with the obligatory twin cams per head.
Whist initially the quality of unleaded fuel available at the time limited power, when super unleaded became available in 1987 the limitation of the engine were removed. In S4 GT guise, the 928’s 5-litre V8 produced 330hp, helped by better valve control. The last model in the line, the 928 GTS, had a longer stroke, increasing capacity to 5.4-litres and boosting power to 350hp. Production ended in 1995 – as did this first generation of road-going V8s from the marque.
It wasn’t until 2002 that the second generation of V8 engines emerged from Weissach, under the bonnet of the equally revolutionary Cayenne. Two such V8s were available; a naturally aspirated 4.5-litre unit in the Cayenne S which produced 340hp, and for the top-of-the-range version a twin-turbo mill based on the same engine which produced 450hp. This made the Cayenne the fastest SUV of its era. The 4.5-litre V8 was helped along by such innovations as intake valve control, increasing torque and power across the rev range.
Three years after the turbocharged eight-cylinder engine made its debut, Porsche went to work to develop it into the engine of the Cayenne Turbo S. With 521hp at 5,500 rpm it made the new SUV the second most powerful production Porsche car ever built – after the Carrera GT.
Power and fuel economy got a boost in 2007 when Porsche introduced more technology to the engine. Direct fuel injection and variable valve timing for intake valves, which meant their stroke could be varied between ten and 3.8mm, increased fuel economy (by 8%) and reduced emissions. A 3mm increase in bore size meant the engine now displaced 4.8-litres. On the turbo model, larger turbines helped increase flexibility. In this guise the Cayenne S produced 385hp and the Turbo 500hp.
In the same year, the Cayenne GTS made its appearance, with an uprated naturally aspirated engine producing 405hp. In 2008, the Cayenne Turbo S was launched with a boosted mill that put 550hp through the wheels, once again earning it the title of fastest SUV.
A new kid on the block
In 2009 Porsche launched the Panamera as its fourth model line. With it came further revisions to the 4.8-litre V8. A new exhaust and improved engine control boosted power of the naturally aspirated model to 400hp, while in the Turbo 500hp was on tap. Engine weight was also reduced by several kilos thanks to the introduction of lightweight alloys for various components. As well as being deployed in the Panamera, these reworked engines were installed into the Cayenne.
As ever with Porsche, development never stops, and as such higher powered versions of the 4.8-litre unit were created. In the Panamera GTS the naturally aspirated engine made 430hp, whilst in its Cayenne equivalent the power was slightly lower at 420hp. The turbo models were fettled too, with the Cayenne turbo gaining 20hp to bring it to 520hp in total. In the Panamera Turbo S engine power was a significant 550hp, whilst the Cayenne got even more power to motivate it, packing 570hp under the bonnet.
3rd Generation – Hyper Drive
Porsche’s ‘hypercar’ – the 918 Spyder – is fundamentally powered by a highly advanced naturally aspirated V8. A completely new unit, the 2013 car not only had the V8 in the middle, but also benefitted from electric drive, making it the first sports car of this nature to implement a hybrid drive system. The engine, however, is quite extraordinary; with 132 hp/litre, it had the world’s highest specific power of a street-legal naturally-aspirated engine, and at the same time it was the lightest production naturally-aspirated V8 engine, weighing 135 kilograms. Inside the eight-cylinder engine with its usual bank angle of 90 degrees was a motorsport-derived flat-plane crankshaft with 180 degree offset crank throws for the connecting rods.
Rev-happy and displacing just 4.6-litres, the V8 (derived from the RS Spyder) produced 608hp at a lofty 8,700rpm. It was also the ‘heart’ of a car, offsetting the silence of electronic drive with its power and sound. Key to this were the “top pipes” – exhausting waste gas directly above the engine (a unique design feature). The top pipes’ greatest technical benefit is optimal heat rejection, because the hot gases are exhausted via the shortest possible path, and exhaust gas back pressure remains low.
This type of HSI engine design – where HSI stands for “hot side inside” – the 918 engine created a definitive foundation for the new eight-cylinder engine of the Panamera. It contains the quintessence of four decades of eight-cylinder V-engines by Porsche.
And with the new Panamera, and its powerplants, very much in the public eye, it’s fair to say we have an awful lot to look forward to.