From a stroke of genius. From strength to strength. The 911 997 Turbo
In 1905, the Swiss engineer, Dr. Alfred Büchi, filed the first ever patent for a turbocharged piston engine. The fundamental principle, now a century old, remains unchanged to this day: to use the energy latent within the exhaust flow from the engine to increase overall performance.
The first turbocharged engine was built in 1910 by the firm of Murray-Willat. The concept was embraced by the aviation industry, which required an effective means of compensating for the loss of power caused by reduced oxygen levels during high-altitude flight.
Porsche was among the first to recognise other benefits of the technology, including higher performance potential from relatively small displacement engines. This would lead to the development of powerful new engines with very modest dimensions and weight.
The basic principle of a turbocharged engine is to use the exhaust gas flow to drive a radial turbine which in turn drives a compressor in the air intake tract. The rotation of the compressor generates a higher intake pressure, thereby delivering a greater amount of oxygen to the engine. With more oxygen available, more fuel can be burnt, and higher performance can be achieved. The density of the air can be further increased by cooling it prior to combustion. The first ‘intercooler’ device on a production Porsche appeared in 1977 on the 911 Turbo 3.3.
The first Porsche racing car to feature turbocharged power made its debut in the early 1970s. The 12-cylinder engine in the legendary 917 used a twin turbo system to achieve a colossal 1,000 bhp. In 1972, the 917/10 with 5-litre turbo engine claimed the North American CanAm championship. In the following season, the 917/30, developing 1,100 bhp from a 5.4-litre unit, became the most powerful racing Porsche of all time.
This invaluable race experience inevitably found its way into our production road car development. Just one year later, in 1974, the 911Turbo was born. Preceded as it was by the 1973 oil crisis, it was considered a bold undertaking by Porsche. As history would show, it was the first of many surprises in the evolution of this legendary car.
The original 911 Turbo featured widened wheel arches as well as specially developed front and rear spoilers. These major aerodynamic refinements were essential requirements given the increased engine performance. Developing 260 bhp, the first 911 Turbo could reach 100 km/h (62 mph) in as little as 5.5 seconds. Maximum torque output of 343 Nm was unprecedented in a 3-litre engine. This exceptional performance necessitated a new gearbox design featuring specially reinforced gears. Thus began a new type of Porsche that would soon acquire mythical status.
The second 911 Turbo, launched in 1977, developed 300 bhp from a 3.3-litre intercooled engine. Brake performance was similarly enhanced, combining four-piston aluminium fixed calipers with cross-drilled discs.
In 1993, Porsche launched the final 911Turbo to feature dedicated rear-wheel drive. Based on the Type 964 platform, it used a 3.6-litre engine to achieve a major boost in output to 360 bhp. Its Type 993 successor, launched in 1995, set a range of new benchmarks in supercar performance. All-wheel drive provided greater active safety as well as better driving dynamics. The system also had a rear-axle bias that retained the familiar Porsche handling characteristics. Twin exhaust turbochargers offered better response and a more harmonious build-up of power.The last 911 Turbo to have an aircooled engine, it offered maximum output of 408 bhp from a 3.6-litre displacement.
The first water-cooled 911 Turbo, the Type 996, made its debut in the year 2000. Also equipped with all-wheel drive, it used VarioCam Plus to achieve a major improvement in all-round fuel economy. The engine capacity remained at 3.6 litres, while output rose to 420 bhp for a maximum speed of 305 km/h (190 mph). The Type 996 model was the first 911 Turbo with the option of Tiptronic S transmission. The subsequent launch of the Turbo S version saw a further rise in output to 450 bhp.
Now, the evolution of this remarkable car has reached a new pinnacle of achievement. Over the following pages, we will explore every aspect of the new 911 Turbo.
Engineering the new 911 Turbo
The primary objective for every 911 Turbo is to challenge the limits of technical feasibility. Not only in terms of performance and dynamics, but also when it comes to ride comfort. On this latest evolution, we’ve completely redesigned a number of systems and components. The result builds on the achievements of the previous 911 Turbo – a car widely acknowledged as the ultimate in sportscar design. As you would expect, the new 911 Turbo meets the highest expectations in terms of engine performance. The classic flat-six unit develops 353 kW (480 bhp) at 6,000 rpm from a 3.6-litre displacement. Maximum torque of 620 Nm is available between 1,950 and 5,000 rpm. To achieve that capability, we’ve combined VarioCam Plus with twin turbocharger units featuring Variable Turbine Geometry (VTG) – a totally new technology on a petrol-engined car. With a standard manual gearbox, the new 911 Turbo requires just 3.9 seconds to reach 100 km/h (62 mph). Equipped with the latest optional Tiptronic S transmission, the car is 0.2 seconds quicker on the standard sprint. Benchmark times to 200 km/h (124 mph) are 12.8 and 12.2 seconds, respectively. Maximum speed with either transmission is 310 km/h (193 mph).
One of the most important engine technologies, appearing for the first time on a Porsche, is Variable Turbine Geometry (see page 32). The main components on this system are the adjustable guide vanes which channel the exhaust flow onto the turbines, enabling higher turbine speeds at lower engine rpm. The most difficult challenge when developing this technology was the high exhaustgas temperature of around 1,000 ºC, which is unique to a petrol engine. This enormous thermal load is considerably greater than the 700 ºC typically encountered on a diesel-powered car. It was only possible to bridge this gap using materials developed for aerospace applications. The primary benefits of Variable Turbine Geometry include faster response, higher torque output from lower engine speeds, and greater top-end power. Maximum torque is also available over a wider engine speed range. By eliminating the problem of ‘turbo lag’, the traditional weakness of the turbocharged engine is finally a thing of the past.
To apply these benefits efficiently to the road, we required another innovation in sportscar design: allwheel drive with Porsche Traction Management (PTM). Using an electronically controlled multi-plate clutch, this intelligent technology provides variable drive to each axle. The front/rear split is continuously adjusted based on current road conditions and driver inputs. Although biased towards the rear, the front receives more power whenever the situation requires. Porsche Traction Management is specifically designed to optimise driving dynamics. The additional traction provided by both the all-wheel drive system and PTM represents a major improvement in active safety, especially in the wet or on snow.
Another benchmark technology on the new 911 Turbo is the standard braking system. The front and rear discs have a generous diameter of 350 mm. On the optional Porsche Ceramic Composite Brake (PCCB), the front diameter is increased to 380 mm.
Other standard features on the new 911 Turbo include a new evolution of Porsche Stability Management (PSM) as well as Porsche Active Suspension Management (PASM) featuring electronic damper control. A limited-slip differential is available for the rear axle as an option.
For even greater performance, the car can be equipped with the optional Sport Chrono Package Turbo. Key features include an ‘overboost’ function which provides as much as 60 Nm of additional torque under acceleration. When the throttle is fully open, the boost pressure is increased temporarily by approximately 0.2 bar. The electronic throttle map is also adjusted to give a more dynamic response to pedal inputs.
Other modifications when ‘Sport’ mode is selected include a major rise in the trigger threshold used by Porsche Stability Management (PSM). The all-wheel drive system featuring PTM provides a similar increase in driver involvement by sending a greater proportion of drive torque directly to the rear wheels. PASM provides a stiffer suspension setup enabling faster turn-in and better road contact.
Another major development on the new 911 Turbo is the car’s lightweight design and construction.The doors and front lid are made from aluminium which offers a range of benefits in terms of both performance and economy. Every gram of weight on every component is there for a specific reason. As a result, the standard model (with six-speed manual gearbox) weighs just 1,585 kg. Even more impressive are the power-to-weight ratio of 302.8 bhp per tonne and surprisingly low fuel consumption.
This powerful potential is, of course, matched by exemplary ride quality on every type of road. This rare combination of performance and comfort is one of the distinguishing features of the 911 Turbo.
Poised for action, yet always relaxed. Designing the 997 Turbo
The extreme capability of the new 911 Turbo is elegantly enclosed in a highly distinctive exterior. While signalling the unique athleticism of the car, it remains unmistakably 911.
The aerodynamics are exceptionally well balanced, with positive downforce at the rear. The drag coefficient is remarkably low at just 0.31. With its streamlined shape and lightweight build, the new 911 Turbo offers excellent fuel economy as well as superlative performance. The standard Bi-Xenon headlights with integral cleaning system are compact, stylish and elegantly incorporated within the new front-end design. The front apron moulding is an entirely new development, featuring high performance LED indicators in the outer air intake ducts. The compact front fog lights are neatly positioned on the outer edges of the front apron.
The side air intakes, to the rear of the doors, provide optimum air delivery to the twin intercooler units. Equally efficient are the cooling air ducts to the front and rear brake assemblies. This enhanced cooling action is an important factor in the excellent performance of the standard braking system.
The body of the car is much wider across the rear than the front. A generous wheel track is combined with wider tyres to achieve enormous lateral grip. The engine lid is another totally new design and features an integral bi-plane rear spoiler. The upper wing element is automatically raised at approximately 120 km/h (75 mph) and lowered at around 60 km/h (37 mph).
The rear wing retracted
The rear wing deployed
The rear apron moulding has also been redesigned to blend with the rest of the car. The side air outlets and fully enclosed twin tailpipes are a further indication of the power within. Black plastic sills along the sides of the body provide effective protection against stone chips.
Elegantly matched to the exterior of the car is the all-new wheel design. The 19-inch forged alloys have a standard two-tone finish as well as wide, low-profile tyres. The standard tyre dimensions are 235/35 ZR 19 (front) and 305/30 ZR 19 (rear). The interior of the car is equally compelling and entirely designed around the driver. The high-quality surfaces include a full leather finish on the standard electric seats as well as the dashboard, doors and rear side panels. Two sports seat options are also available, one featuring adaptive adjustment. The standard equipment package includes a new gear-knob design – created exclusively for the 911 Turbo – and a three-spoke sports steering wheel featuring 40 mm of height and reach adjustment.
The overall design of the new 911 Turbo marks another new phase in the ongoing evolution of this remarkable car. Wholly integral to the fundamental vehicle concept, every detail is a direct expression of power, composure and comfort. Some say power is all about muscle. For us, it starts with the mind.
The Engine. Heart and soul of the new 911 Turbo
Every 911 shares the same fundamental engine characteristics. Key among these are the ‘flat-six’ cylinder layout and rear-mounted installation.
There is, however, one essential feature that is unique to the 911 Turbo. The twin turbocharger system that gives the car its name now includes Variable Turbine Geometry (see page 32). Thus equipped, the 3.6-litre engine develops 353 kW (480 bhp) at 6,000 rpm. Weighing 1,585 kg, the standard 911 Turbo (with manual gearbox) has an excellent power-to-weight ratio of 302.8 bhp per tonne. Specific power output is 133 bhp per litre of engine displacement.
Maximum torque is a phenomenal 620 Nm, rising to 680 Nm with the overboost function in the optional Sport Chrono Package Turbo (see page 60). Thanks to VarioCam Plus (see page 38) and the new turbocharger system, all of that torque is fully available between 1,950 and 5,000 rpm.
The resulting acceleration is inspirationally quick. Equipped with Tiptronic S, the new 911 Turbo requires just 3.7 seconds to reach 100 km/h (62 mph), and just 12.2 seconds for 200 km/h (124 mph). Facilitating this performance is the additional traction provided by the new electronically controlled all-wheel drive system (see page 48). In appropriate track conditions, the car’s maximum speed is 310 km/h (193 mph).
The six-cylinder boxer engine is a highly compact unit offering excellent cylinder charging and torque characteristics as well as optimum balance and minimal vibration. With the cylinders arranged horizontally on either side of the crankshaft, the layout is key to the car’s low centre of gravity.
The alloy crankcase consists of two main sections, each containing one bank of cylinders. The crankshaft runs in eight main bearings and is driven by forged connecting rods. For optimum durability, we’ve used forged aluminium pistons running in Nikasil-coated aluminium liners and featuring individual oil-spray cooling. Key benefits include lower frictional resistance and longer service life.
The cylinder heads are made from a lightweight alloy which is extremely resistant to high temperature. Each bank of cylinders has two overhead camshafts driving a set of four valves – two inlet and two exhaust – on each individual cylinder. The valves are arranged in a ‘V’ configuration and feature a highly efficient dual-spring design. Engine performance is further enhanced with the aid of both Variable Turbine Geometry (VTG – see below) and VarioCam Plus (variable valve timing and lift on inlet side – see below). The benefits are not only greater power and torque, but also better fuel economy and lower emissions.
This classic dry-sump system with separate oil reservoir ensures consistent oil pressures throughout the engine. In doing so, it compensates for even the most extreme and prolonged gravitational loads.
Main rotating assembly and valve gear
After passing through the engine, every drop of oil is returned directly to the external reservoir. The flow is driven by two pairs of scavenge pumps in the cylinder heads and a further two pumps in the crankcase. Gas is removed from the returning oil by means of a defoaming device in the reservoir. As a result, the oil level in the reservoir remains virtually constant at all times. The oil is returned to the lubrication points in the engine by means of a dedicated oil-feed pump. With a further scavenge pump in each of the twin turbocharger units, the new 911 Turbo has a total of nine separate pumps to drive the lubrication system.
The oil level can be checked from inside the car via the standard on-board computer. This solution is not only cleaner and more convenient than a conventional dipstick, it is also significantly more accurate.
Variable Turbine Geometry (VTG)
Creating the optimum turbo for every scenario. The 911 Turbo has always been synonymous with performance. Now the car is more capable than ever thanks to a new twin turbo system featuring Variable Turbine Geometry (VTG).
Turbocharger with Variable Turbine Geometry (VTG)
On a conventional turbocharger, the exhaust flow drives a turbine that is connected to a compressor in the air intake tract. By ‘squeezing’ the incoming air, the amount of oxygen in a given volume is increased. Since compression also causes an increase in temperature, the air must be passed through an ‘intercooler’ unit. With more oxygen present in each cylinder charge, more fuel can be burnt yielding greater energy. Since higher exhaust pressures generate corresponding loads on the intake side, the intake pressure must be carefully controlled in order to protect the engine. On the new 911 Turbo, the ‘boost pressure’ is limited using ‘wastegate’ valves that bypass excess pressure around the twin exhaust turbines.
Another important factor is the size of the turbo unit. Since a smaller turbine has a lower mass, it generally responds more quickly to increasing pressure, spinning up easily to its optimum speed. The key disadvantage of using a smaller turbo is that the backpressure generated at higher engine speeds causes a significant reduction in performance. Resistance is caused by the smaller cross-sectional area through which the exhaust is required to flow.
Larger turbo units, which create lower back-pressure at higher rpm, take considerably longer to spin up under power due to the large cross-sectional area and relative inertia of the heavier turbine. Generally, this type of turbo will only be effective in the medium rpm range. This phenomenon, known as ‘turbo lag’, means there is virtually no turbocharging effect at lower engine speeds. To overcome this problem, the twin water-cooled turbochargers on the new 911 Turbo feature Variable Turbine Geometry (VTG). With this technology, the gas-flow from the engine is channelled onto the turbines via electronically adjustable guide vanes. By changing the vane angle, the system can replicate the geometry in all types of turbo, large or small.
Turbocharger guide vane adjuster
With Variable Turbine Geometry (VTG), it is possible to achieve higher turbine speeds, and thus higher boost pressure, at lower engine rpm. Cylinder charging is significantly improved, with a corresponding increase in both power and torque. Maximum torque is reached at lower rpm and is retained across a wider rev range. A full 620 Nm is available from as low as 1,950 rpm up to 5,000 rpm. Every throttle input is met with exceptional response and phenomenal acceleration. When the boost pressure reaches its maximum value, the guide vanes are opened further. By varying the vane angle, it is possible to achieve the required boost pressure over the entire engine speed range. As a result, there is no need for excess pressure valves as found on conventional turbocharged engines.
The capability of the engine can be further enhanced by selecting ‘Sport’ mode on the optional Sport Chrono Package Turbo (see page 60). Under full acceleration, the boost is temporarily increased by approximately 0.2 bar. During this phase, the engine develops as much as 60 Nm of additional torque.
Matching the superlative performance of the car is the efficiency with which it is generated. In spite of the increase in power and torque, the new 911 Turbo offers a further reduction in fuel consumption.
Guide vanes closed
Guide vanes closed
Guide vanes open
Guide vanes open
The capability of the engine can be further enhanced by selecting ‘Sport’ mode on the optional Sport Chrono Package Turbo (see page 60). Under full acceleration, the boost is temporarily increased by approximately 0.2 bar. During this phase, the engine develops as much as 60 Nm of additional torque. Matching the superlative performance of the car is the efficiency with which it is generated. In spite of the increase in power and torque, the new 911 Turbo offers a further reduction in fuel consumption.
- Turbine casing
- Movable guide vanes
- Turbine wheel
- Electric motor for guide vane adjustment
- Guide vane adjuster
- Compressor casing
- Compressor wheel
- Excess-pressure valve
- Oil inlet
- Coolant inlet
Optimum valve timing, optimum valve lift, in all load conditions.
VarioCam Plus combines variable valve timing with two-stage valve lift on each inlet camshaft. The resulting benefits include greater power and torque at all engine speeds, as well as smoother running, better fuel economy and fewer exhaust emissions.
Essentially, VarioCam Plus offers two engines in one. The first is designed for normal road driving, the second for high-performance use. The system switches seamlessly between the two as driver inputs change. All operations are centrally controlled by the engine management system. The result: emphatic acceleration and smoother running.
The two-stage lift mechanism on each inlet valve consists of an electro-hydraulically switchable tappet. Each of the 12 tappets has two concentric lifters which can be locked together by means of a pin. When the tappets are locked, the outermost ring – which is driven by two large profile cams – is in direct contact with the valve. When the pin is removed, the innermost lifter – operated by a smaller cam lobe – has sole influence over the amount of valve lift.The timing of each valve is steplessly controlled by means of an electro-hydraulic rotary vane adjuster at the head of the corresponding camshaft.
To improve responsiveness during warm-up in cold weather, VarioCam Plus will select the higher valve lift setting and retard valve timing.
At medium revs and low engine loads, the lower valve lift setting is selected and timing advanced in order to reduce fuel consumption and emissions. The economy of the engine is particularly enhanced at lower engine speeds. For maximum power and torque, the higher lift setting is selected and the timing of the valves is advanced.
From the driver’s perspective, the results are clear: copious torque with exceptional fuel economy, particularly in comparison with much larger yet similarly rated engines.
The 911 Turbo engine features cross-flow water cooling with fully integrated coolant management. This technology ensures a consistent flow of coolant to each of the engine’s cylinders. All coolant passages are integral to the block, thus eliminating the need for external hoses. Each cylinder receives a fresh supply of coolant which has not been pre-warmed by the engine. As well as improving reliability, this helps to minimise maintenance requirements. Waste heat from the oil is transferred to the coolant via two oil/water heat exchangers. The coolant is routed through twin radiator modules ahead of the front wheels and a centrally placed unit in the nose.
Optimum performance is assured at all times with the aid of the Motronic ME7.8.1 engine management system. On the new 911Turbo, this powerful ECU is responsible for all engine-related functions and assemblies (see diagram). Key among these are the Variable Turbine Geometry (VTG), VarioCam Plus and electronic throttle system – one of the essential prerequisites for the standard Porsche Stability Management (PSM). The results: optimum economy, emissions and performance, regardless of driving style.
Another important task performed by the engine management system is cylinder-specific knock control. By preventing pre-ignition at high engine speeds, this function can avert costly damage to the pistons and cylinders. Since temperatures tend to vary in different parts of the engine, each cylinder is monitored separately. If a risk is detected, the individual ignition timing is adjusted.
The EU-compliant on-board diagnostics system provides continuous fault detection and early warning for the exhaust and fuel supply systems. The resulting benefits are active prevention of harmful emissions as well as consistent rates of fuel consumption.