2009 Porsche 911 GT3 RS

PORSCHE GT3/GT3 RS

Racing runs deep in the bloodlines of every Porsche built since the company's inception. The marque's hallmark of extraordinary performance on the finest roads of the world, in the hands of the most skilled and talented enthusiast drivers has its basis on the race track.
Not surprisingly many Porsche owners use their vehicles not only for stylish, exceedingly capable personal transportation, but also for various types of motorsports competition. The Porsche 911 GT3 and the 911 GT3 RS were created for those most serious competitors.





Essence of high performance
Bred for the driver who craves track days as much as street drives, the Porsche 911 GT3 and GT3 RS are powered by Porsche's most potent naturally aspirated six-cylinder engine: a 415-horsepower 3.6-liter with an 8400-rpm redline. As befits a race-ready machine, the engine has a special, low-restriction exhaust system that still keeps sound levels within public-road legal limits. The 911 GT3 and GT3 RS come only with a special six-speed manual gearbox with ratios designed to optimize the engine's extended rev range. The astounding results are the GT3's zero-to-60 mph (0-99 kph) run in just 4.1 seconds. The car continues to 99 mph (160 kph) in only 8.7 seconds,
finally topping out at the test track at 193 mph (310 kph).

The lighter, even more athletic GT3 RS has been tweaked to make the zero-to-60 mph (99 kph) sprint in an amazing 4.0 seconds, charging to 99 mph (160 kmh) in 8.5 seconds. Track-proven top speed matches the GT3 at 193 mph (310 kph).



Únique, track-bred aerodynamics
Úsing what they learned in the wind tunnel while honing the shape of the 911 GT3 Cup, Porsche aerodynamicists ensured the road-going cars would enjoy unparalleled aerodynamics. Despite its wide haunches, the GT3 has a remarkably low drag coefficient of only 0.29. The wider-still GT3 RS boasts a Cd of only 0.30. More critically, the cars have stupendous downforce throughout their speed range.

The monocoque structure carries a body with aluminum front lid and doors, and a plastic composite rear decklid. The remaining major body components are lightweight, hot-galvanized steel.

Viewed from any angle, the brawny, wide-shouldered GT3 and GT3 RS look like no other 911 Coupes, though they are clearly related. The nose boasts an upper air outlet to vent heated air from the central radiator, rather than allow that air to exit beneath the car, as with other models. In the rear, besides the unique exhaust pipes, these cars are instantly recognizable by the fixed rear spoiler.

Low weight for supreme agility
Every piece of the 911 GT3 and the GT3 RS has been carefully evaluated for reduced mass and maximum strength. The results are clear: the GT3 has a curb weight of just 3075 pounds (1395 kg). The even-more lithe GT3 RS shaves 44 pounds (20 kg) from that and tips the scales at 3031 pounds (1375 kg).

Safe occupant comfort
As true race-track contenders, the cockpits of the 911 GT3 and GT3 RS differ from those in other 911 Coupes. Most critically, the cars are two-seaters. There is no rear seat. The front seats are deeply bolstered and feature special upholstery to help keep the occupants from sliding in the seats.

But in a critical way, the GT3 and GT3 RS are identical to the rest of the 911 range. The occupants are protected by six airbags. There are two frontal impact airbags and two thoraxprotecting side-impact airbags, one in each seatback's outer bolster. There are also headprotecting curtain-style side-impact airbags as part of the Porsche Side Impact Protection (POSIP) system which deploy upward from both doors' windowsills.

Agility and stability
Both GT3 and GT3 RS are fully equipped to provide maximum road-holding and day-to-day comfort thanks to their Porsche Active Suspension Management (PASM) adjustable suspension. Each shock is individually adjusted by the system's electronic control module. The mapping software used in the PASM controller for these cars was created to give the cars a normally extremely sporting behavior for the road with an additional handling setup for the track.

Traction, critical traction
To ensure that even the most skilled driver can extract maximum dynamic performance from the cars, the GT3 and GT3 RS have a dizzying array of traction-enhancing features. The most critical are the huge 235/35ZR19 front and 305/30ZR19 rear sport tires on special light-alloy wheels. As with other 911 Coupes, to help save weight the GT3 and GT3 RS carry no spare tire. Instead the cars have a small electric air compressor and emergency tire sealant to allow the driver to safely make it to a service station or the pits to have the tire replaced or properly repaired. To keep the driver apprised of tire conditions, the cars are also equipped with Porsche's Tire Pressure Monitor system which constantly monitors the inflation pressures of all four tires and alerts the driver to changes.

The tires benefit from three electronic control systems: Automatic Brake Differential (ABD), Automatic Slip Control (ASC), and Engine Drag Control (EDC). All under the purview of a Traction Control computer, there are two different sets of control maps. And, critical for the serious racer, the system can be completely deactivated.

The standard limited-slip differential offers an asymmetric limited-slip function of 28 percent under load and 40 percent in overrun, and boasts components from Carrera GT.

Stupendous stopping
The four-wheel disc antilock brakes system consists of four 13.78-inch diameter rotors. All are cross drilled and internally vented. The front brakes are clamped by six-piston aluminum monobloc calipers. Those in the rear are gripped by four-piston aluminum monobloc rotors. For those seeking even greater braking power, the GT3 and GT3 RS can be equipped with Porsche Ceramic Composite Brakes (PCCB) as an option.

Proud history
Porsche has used the GT designation on various models through its history and awards that racing-derived label seriously. Any Porsche with a GT designation is a race-bred machine. Likewise, the RS suffix has its roots in motorsports as well. The company introduced its first 911 RS at the Paris Motor Show in 1972. The car was the Carrera RS 2.7 and, as demanded by racing regulations of the day, weighed only 2117 pounds (1000 kg), complete with flared wheel arches and rear spoiler. It was Germany's fastest production car.

The company intended to manufacture only 500 units as per motorsports homologation rules. But demand among enthusiasts was so strong, that over the car's nine-month production run 1525 were sold. One of those 1525 was the overall winner of the Targa Florio in 1973, the last time that glorious race was run.

A body built for speed
As a starting point for the latest 911 GT3 and GT3 RS, Porsche body engineers chose the body-inwhite of the current 911 Carrera 4, while the outer shell of the body has been carried over from the 911 Carrera. The structure used in the current 911 Carrera 4 models, designated internally as 997, is eight percent stiffer torsionally and has 40 percent more flexural stiffness than the previous model GT3.

To reduce weight, the GT3 and GT3 RS have no rear seats, and use aluminum doors and front decklid, in place of the Carrera model's steel components. Engineers also created a unique rear decklid of lightweight plastic. Únlike other 911 models, the rear wings of the GT3 and GT3 RS do not automatically deploy and retract based on road speed. Instead the cars have fixed, but adjustable angle rear spoilers. To help shave even more weight, the GT3 RS has a rear wing made of carbon fiber.

Tuned in the wind tunnel
Porsche aerodynamicists left no stone unturned in their quest to optimize airflow over, under and around the GT3 and GT3 RS bodies. The fruits of their labors produced a coefficient of drag of only 0.29 for the GT3 and 0.30 for the GT3 RS.

The GT3 RS has a slightly wider rear track than the GT3, which accounts for the marginal increase in drag coefficient. Compared to the GT3, the GT3 RS is 1.71 inches (44 mm) wider overall and has a rear track that is 1.34 inches (34 mm) wider. Because of its unique and designed-for-racing rear subframe and unique front lip spoiler, the GT3 RS also is slightly longer, by 0.59 inches (13 mm) overall and by 0.19 inches (5 mm) in wheelbase.

The front end of the 911 GT3 and GT3 RS is characterized by extra-wide cooling air intakes positioned at the outer edges. These scoops ensure a consistent and more-than adequate supply of cooling air. Their design and configuration with vertically arranged bars add to the cars' singular appearance and character.

The large center intake protrudes all the way to the lip of the front spoiler, forming a slight wedge to improve aerodynamic efficiency. Aesthetically, the joint between the front section and the spoiler lip serves to visually accentuate the central cooling air intake.

Another aerodynamic design feature unique to the GT3 and GT3 RS is an air outlet in front of the luggage compartment lid. This opening lets air passing through the radiator exit over the nose the car, rather than beneath, reducing front-end lift forces at high speeds.

Downforce is provided by the front and rear sections, the shells in the wheel arches, the rear lid and wing, and the underbody panels. The new front end, with its separate spoiler lip and upper air exhaust vent, reduces the flow of air beneath the car.

The cooling-air openings are positioned to guide air coming out from behind the side radiators to the brakes. This makes a significant contribution to reducing lift forces on the front axle. To ensure optimum airflow in the rear, small spoilers at the wheels improve flow and reduce lift. The aerodynamic improvements made at both the front and the rear of the car are carefully matched and coordinated for optimum balance.

Apart from the rear wing's new profile, there's a flap at its bottom and winglets at its side. The wing angle may be adjusted by either three degrees or six degrees, and the side winglets are also adjustable—a benefit at the track.

Improving both the cars' center of gravity and aerodynamic efficiency, the GT3 and GT3 RS sit 1.18 inch (30 mm) lower than the current 911 Carrera. Like the current 997 version of the 911 Carrera models, the GT3 and GT3 RS have an underbody that's virtually enclosed for optimum downforce and minimal lift. The GT3 and GT3 RS sport additional vents in the rear of the underbody cover to cool the rear brakes.

A look like no other 911
Viewed from the side, both the GT3 and GT3 RS are immediately recognizable as members of the 911 series. But they are clearly distinct in that series.

The most distinguishing features are the cars' very low stance, the non-retractable muscular rear wing, and the special GT3 and GT3 RS single-piece 19-inch wheels.

The fixed rear wing is a traditional feature of all GT3 models. The vertical sections on the wing follow the contours of the car's rear, perfectly matching the curve of the rear wheel arches. The additional streamlining flap at the bottom of the wing's vertical panels not only integrates the rear wing into the overall design, but also makes a significant contribution to the car's aerodynamics. Besides the familiar fixed wing, the 911 GT3 and GT3 RS have centrally mounted tailpipes, and additional air outlet openings at the rear. The large-diameter twin tailpipes were carried over from the 911 Carrera Cup race cars, and optimize the aerodynamic flow of the exhaust system besides
giving the rear of the cars a powerful look.

Passenger cabin and race car cockpit
The starkest and most obvious difference between the interiors of the GT3 and GT3 RS when compared with every other model in the 911 range is the lack of rear seats. Clearly a car meant for the race track has no need for them and their presence only adds unnecessary weight. More subtle, but critical, distinctions between the interior of the GT3 and GT3 RS and the remainder of the 911 family are the car's steering wheels and trim materials. The GT3 and GT3 RS boast Alcantara® trim on the steering-wheel rim and handbrake lever.

The steering wheel also features a special yellow section at the top center position. This traditional racing element allows the driver to instantly know if the front wheels are pointing straight ahead. As with other 911 models, the steering wheel offers an adjustment range of 1.57 inches (40 mm) of both height and reach.

In addition, the middle sections of the seats are also covered in Alcantara®. This high-quality and inherently grippy material helps keep occupants from sliding in the seats during hard cornering. The GT3 and GT3 RS are trimmed in either black or dark grey leather as standard. Optionally, owners can select other leather, including the new for 2008 Carrera Red natural leather. The instrument clusters of the GT3 and GT3 RS are very reminiscent of the one in the astounding Carrera GT. The gauge needles and scales are finished in yellow and the tachometer is highlighted
by a titanium-colored face. The rev counters carry each car's model name, GT3 or GT3 RS.

Safe by design
Sharing the high- and ultra-high-strength steel, as well as improvements in spot-welding and bonding, used in the 911 Carrera Coupe, the GT3 and GT3 RS bodies are extremely torsionally rigid and flex resistant while still being lightweight.

Particular attention was paid in designing and engineering the junction of the A-pillars and the roof frame, as well as the safety structure involved in head-on and offset collisions, including the transition between the door and B-pillars. Forces in a collision can be transferred through the door, around the passenger compartment to the rear of the car.

A bulkhead crossbar at the front of the car is made from high-strength boron steel and special assembly processes were developed to minimize intrusion in to the foot well in an offset collision.

Six airbags and POSIP
The 911 GT3 and GT3 RS are equipped with six airbags. There are two front-impact airbags, two front-seat mounted thorax-protecting side-impact airbags and the two curtain-style door-mounted side-impact airbags that are part of the Porsche Side Impact Protection (POSIP) system. The frontal airbags are full-size, two-stage front units featuring an organic-based propellant. This propellant reduces the stored airbags' size and weight, and aids in their recyclability.

The front passenger seat features sensors that accommodate child safety seats. Should the sensors detect a child sitting in that seat, the airbag is defeated.

The POSIP boasts head airbags that deploy upward from their housings in the door windowsills. These airbags provide a flat cushion that inflates to nearly 500 cu.-in. (8 liters) and are designed to help protect the heads of the driver and front-seat passenger from broken glass and objects that might enter through the window in the event of an accident.

Better to avoid
Perhaps even more critically on the race track than on the road, avoiding an accident is far preferable than relying on safety devices to survive it. Porsche engineers took special steps to ensure that the GT3 and GT3 RS offer the highest possible levels of agility, stability and driver response.

Building upon a super-wide stance—the GT3 RS has a 58.94-inch (1497-mm) front and a 61.34-inch (1558- mm) rear track—the suspension engineers gave the GT3 and GT3 RS a secure footprint. The engineers then specified a lightweight and technologically advanced suspension system and a low center of gravity for optimum agility and driver confidence assuring stability.

Race ready front suspension
The GT3 and GT3 RS boast a specially tweaked version of the Porsche independent suspension. In front, are spring-strut axles that use separately mounted longitudinal and track control arms to assure precise wheel guidance while controlling body roll. The shocks are mono-tube, gas-charged electronically controlled units as part of the standard-equipment Porsche Active Suspension Management (PASM) system.

The front springs and shocks are firmer than those under other 911 models. In addition, the front PASM shock struts have an additional external thread and a height-adjustable spring plate. This allows a fine tuning of ride and individual wheel loads at the race track.

The GT3 also features cylindrical springs on the front axle with a linear control map. The geometric configuration of the springs and spring plates is based on racing spring standards, allowing relatively easy and straightforward adjustment of the suspension for motorsport events on closed circuits. The support mount allows two wheel positions for road and racing tires with their different camber. Fine adjustment of wheel camber is provided by adjustment discs on the lower, split-track control arm.

The GT3 features an adjustable front antiroll bar. There are five different positions for the bar to be set to. Adjustment is via alternate mounting points on the antiroll bar bracket located on the thrust rods between the bar and the wheel mounts. These options in adjusting the suspension setup of the GT3 are intended exclusively for motorsport, preparing the car in racing trim for the individual requirements of different tracks and circuits.

Bringing up the rear
In the rear, the GT3 and GT3 RS have a five-arm, spring-strut suspension with longitudinal and track control arms. In its basic configuration and features, the rear axle of these cars is the same as the rear axle on the current 911 Carrera, but with a firmer set-up. However, the GT3 RS differs from the GT3 with a special split rear track control arms designed with competition in mind. Also, due to the rigors of motorsports, the rear axle has been upgraded at various points, including replacing the standard rubber longitudinal arms' rubber bushings with metal ones. Apart
from giving the rear axle firmer support to the body of the car, this modification also raises the pivot point 0.24 inch (6 mm).

The result is further enhancement of the cars' kinematics with an even smaller change in wheel camber and caster when the springs are under pressure.

Similar to the front shocks, the rear PASM shock struts feature an additional outer thread and a height-adjustable spring plate. Likewise, the rear antiroll bar is also adjustable for track needs, offering three different positions.

Purposeful PASM
Though the essence of the Porsche Active Suspension Management (PASM) used on the GT3 and GT3 RS is the same as it is on every other Porsche, its specifics are very different. While the PASM for the road cars offers the driver a choice of a comfort-based Normal setting and a firmer, more dynamic Sport option, the primary objective in the GT3 and GT3 RS is to give the car extremely sporting behavior on the road. Its Sport setting is designed for the extreme handling demands of racing.

As with other models, the PASM's normal setting in the GT3 and GT3 RS has the electronic intelligence to increase firmness as the driver begins driving faster and more aggressively. Set to the Sport mode, PASM allows a more precise driving style by reducing body movements to a minimum. With the Sport mode activated, the shocks switch immediately to a firmer set-up to help ensure excellent agility on smooth surfaces together with a further enhancement of steering precision. Whenever the system is set in this mode and detects a rougher road surface, in
milliseconds, it switches over to a softer set-up within the Sport control map in order to improve road contact.

And thanks to the sophisticated integration of all the electronic controls on the GT3 and GT3 RS, a bonus of switching from Normal to Sport modes is a boost in engine output. Hitting the Sport button activates a special engine control map which increases torque by approximately 11 lb.-ft. from 3000 to 4250 rpm.

Variable-ratio steering
The GT3 and GT3 RS use the same variable-ratio, rack-and-pinion steering as the current 911 Carrera. This both increases agility and stability at higher speed maneuvers and reduces steering effort at slow speeds.

When the steering wheel is turned within 30 degrees of center, the ratio is similar to that on the previous generation 911. This helps provide a smooth and calm driving experience, even on rough surfaces. However, when the steering wheel angle exceeds 30 degrees, the ratio becomes more direct, reducing lock-to-lock from 2.98 on the previous 996 GT3 to 2.62 turns. This gives the driver better control both on winding roads and in slow-speed parking maneuvers.

Real stick-to-it ability
To ensure optimum traction and all-speed stability, the GT3 and GT3 RS come standard with a STET differential. Úsing components developed for the awesome Carrera GT, the limited-slip differential offers an asymmetric limited-slip function of 28 percent under load and 40 percent in overrun.

In addition, the GT3 and GT3 RS also are equipped with driver-defeatable Traction Control (TC) as standard. TC helps to keep the car properly on path and help to ensure stability, particularly in bad weather or while running on a road or track with dissimilar surfaces under each side of the car. The Traction Control system is similar to the one developed for the Carrera GT.

The system consists of Automatic Brake Differential (ABD), Automatic Slip Control (ASC) and Engine Drag Control (EDC). All three work together as a single unit. The result is a stable car under heavy acceleration, at speed and under heavy braking (thanks to ABS).

If one of the drive wheels begins spinning, ABD applies the braking force on the wheel with higher slip. Should both wheels be spinning, ASC reacts within fractions of a second, instructing the engine control unit to reduce power by reducing throttle and retarding ignition as needed until the wheels regain traction. If the ASC intervenes, its dash warning light will flash.

Engine Drag Control (EDC) is a special function within ASC. This control system cuts in when the rear wheels threaten to lose their lateral stability, as after a downshift on a slippery road. EDC automatically applies throttle to regain stability.

As with other Porsche dynamic driving enhancements, the may deactivate the Traction Control system completely by pressing the TC OFF button. When off, a warning light on the dash glows.

Beyond ample braking power
Like all Porsche vehicles, the GT3 and GT3 RS boast four-wheel disc, antilock brakes. All four discs on both cars are cross-drilled and vented internally for optimum performance even under track racing conditions.

Commensurate with the cars' stupendous performance potentials and race-track intent, the front rotors have a 13.78-inches (350-mm) diameter and are 1.34-inches (34-mm) thick. The rear rotors are the same diameter as the fronts, though thinner: 1.10-inch (28-mm) thick. The front rotors are clamped by six-piston monobloc aluminum calipers. The rears are grabbed by four-piston monobloc aluminum calipers. To reduce the transmission of heat from the brakes to the hydraulic fluid, the caliper pistons are thermally disconnected and insulated by ceramic inserts.

Brake air spoilers and air guidance blades ensure highly efficient ventilation and improved brake cooling. The guidance blades direct the majority of the air flowing behind the radiators through the wheel arches directly to the brake system.

In addition, with their dynamic capabilities, the cars are equipped the same tandem power brake servo and large-bore brake master cylinder as the 911 Carrera 4S, with a 1.06-inch (26.99 mm)piston diameter.

Greater stopping power available
Drivers desiring even greater stopping performance than the already well-renowned Porsche brakescan specify Porsche Ceramic Composite Brakes (PCCB). These race-bred brakes are available as an option on both the GT3 and GT3 RS.

Developed for the extreme use of motorsports, PCCB replaces the standard metal brake rotors with rear 13.78-inch (350-mm) ceramic discs. Besides delivering otherwise unobtainable levels of consistently superb braking performance under repeated heavy use, the ceramic rotors weigh approximately 50 percent less than the iron ones. PCCB reduces the car's unsprung mass by 34.4 pounds (15.6 kg).

In their latest iteration, Porsche Ceramic Composite Brakes are more rigid than previously while providing more interior cooling ducts. The newest brakes have increased fiber reinforcement of the friction surface, significantly enhancing resistance to abrasion under high loads.

Reliable vacuum assist
As with the brake systems on many cars, the GT3 and GT3 RS have vacuum-assisted braking. However, unlike most, the Porsche vehicles do not rely on intake-manifold vacuum for that assist. These cars have a mechanical vacuum pump driven by the right-hand cylinder bank's exhaust camshaft. The vacuum pump ensures a constant and reliable source of braking assist, regardless of ambient air pressure or steady open-throttle driving.

Serious tires and wheels—but no heavy spare
Porsche suspension engineers worked closely with tire suppliers to develop the high-performance rubber for the GT3 and GT3 RS. These tires are made of unique tread compound on a special fabric body.

The tires offer supreme lateral dynamic reserves, particularly on dry surfaces, and the tires are fully suited for track use. The tires also boast substantial wet grip, but due to their shallow treaddepth coupled with their extraordinary footprint, the risk of aquaplaning on very wet roads is increased.

The cars wear 235/35 ZR19 tires in front and larger 305/30 ZR19 rear tires. The tires are mounted on unique light-alloy 19-inch diameter GT3 wheels. The front wheels are 8.5-inches wide. The rears are 12 inches wide.

As with other 911 models, the GT3 and GT3 RS save 22 pounds (10 kg) by carrying no spare tire, jack or tire-changing tools. Instead the cars are equipped with a small electric air compressor and tire sealant allowing the emergency repair of a small puncture.

This gives the driver the safe opportunity to drive at speeds up to 50 mph (80 kph) to a service station or back to the pits to have the tire properly repaired or replaced.

Peace of mind from a tire-pressure monitor
To ensure optimum safety, fuel economy and performance, Porsche engineers provide the GT3 and GT3 RS a standard Tire Pressure Monitoring System (TPMS). This system uses sensors at each wheel to constantly monitor inflation pressures. The system offers the driver two levels of warning should it detect a problem.

If any tire shows a pressure drop of more than 2.9 psi but less than 5.8 psi from specifications, a text message in white lettering shows in the tachometer. This warning appears for ten seconds each time the car is started.

If pressure drops more than 5.8 psi, or if inflation pressure drops at a rate of 2.9 psi or more per minute, the warning becomes more urgent and is displayed in red text. This warning appears as soon as the respective values are exceeded, whether the vehicle is stationary or moving.

The most powerful naturally aspirated Porsche engine
Teamed with the GT3's and GT3 RS's race-bred chassis is a unique 3.6-liter horizontally opposed six-cylinder engine. The engine in these cars has its basis in the engine Porsche developed originally for the 911 GT1 and now boasts the same performance-enhancing technologies found on the engines used in the Porsche GT3 Cup and GT3 RSR pure racers.

Developing 415 horsepower at 7600 rpm and 300 lb.-ft. of torque at 5500 rpm, this Porsche engine is the most potent non-turbocharged powerplant. Developing a specific output of 115.3 horsepower per liter, the engine boasts a redline of 8400 rpm.

Critical in racing, the GT3 boasts a superb power-to-weight ratio of only 7.4 pounds per horsepower. The lighter-still GT3 RS improves that to 7.3 lb./hp. That kind of advantage allows the GT3 to run from zero to 60 mph (99 kph) in only 4.1 seconds, and to 99 mph (160 kph) in 8.7 seconds. The GT3 RS is a shade quicker, driving to 60 mph (99 kmph) in 4.0 seconds and to 99 mph (160 kph) in only 8.5 seconds. Both cars share a top track speed of 193 mph (310 kmph).

Road ready, too
As impressive as the cars' astounding acceleration and maximum top speeds is the fact that both the 911 GT3 and GT3 RS need pay no gas guzzler penalty. In fact, the GT3 RS and the GT3 are rated at 15 mpg in the city and 22 mpg on the highway by the EPA. Also important is the fact that the engines' exhaust are so clean, both cars are certified as Low Emissions Vehicles, category two (LEV-II).

Both quick and high-revving
Over and above the efficient power and torque of this compact engine, the 3.6-liter responds instantly to the driver's throttle demands, throughout the engine's speed range, right up to the 8400-rpm limit.

Porsche engineers assiduously reduced mass and the mechanical loads acting on the engine's moving parts, particularly the pistons, connecting rods and crankshaft. The forged pistons are a unique shape for improved combustion and their piston pins are one mm narrower than otherwise, at 21 mm diameter. This seemingly minor refinement reduced the weight of each piston and pin assembly by 30 grams.

The 131.5-mm long connecting rods are titanium and 1 mm longer than the ones used in the previous version of the engine. This added length allows a smoother transition of reciprocating force from the connecting rods to the crankshaft, while reducing loads. Each connecting rod weighs just 418 grams, approximately seven percent less than comparable size steel connecting rods.

The crankshaft spins in eight bearings and has also been lightened over its predecessor. By revising the design of the crankshaft's webs, Porsche engineers saved another 700 grams. The crankshaft bearings are now also hardened in a nitro-carbonating process.

Special sandwich
The engine block is a vertically split, light alloy crankcase, like the previous generation. The cylinder cases, cylinder heads and camshaft cases on each side are combined to form one unit, increasing the engine's torsional stiffness. This 'sandwich' design differs from the one used in other 911 Carrera engines by the fact that the cylinder cases are not connected with each half of the crankcase.

Porsche engineers chose this design because the power unit of the GT3 serves as a homologation engine for motorsports, and this elaborate configuration is used to quickly adapt to any changes in engine-size categories.

The cylinder cases are made of a light alloy featuring aluminum, with Nikasil®-coated liners. For improved efficiency, including better fuel economy, the engine's compression ratio was raised to 12.0:1.

The cylinder heads are made of a temperature-resistant light alloy, and are nearly identical to the cylinder heads on the former model. The exhaust valve rings are now cooled directly by coolant running through an additional duct, and heat dissipation is further enhanced through the use of sodium-filled exhaust valves.

The increase in power and performance obviously means higher temperatures and thermal loads within the new GT3 power unit. To offset these higher temperatures, Porsche development engineers have opted for a larger water pump and a radiator with larger surfaces.

Dry sump lubrication from and for racing
Given the exceedingly high-performance intent of the 911 GT3 and GT3 RS, every element of the cars must withstand extended periods of high levels of lateral acceleration. Drawing from decades of racing success, Porsche engineers ensured the cars' engines would always be adequately lubricated, even under the most extreme driving conditions.

This is guaranteed by integrated dry sump lubrication incorporating two re-delivery pumps and a pressure pump. The lubricant is cooled by an oil/water heat exchanger.

The three-element oil pump is driven by the crankshaft via a layshaft and a connecting shaft. A pressure pump supplies pressurized oil to the engine's lubricating points. This supply pump extracts engine oil from a separate oil tank, sending the oil through an oil/water heat exchanger and oil filter before continuing into the engine oil circuit. The other two pump segments draw out the oil accumulating in the crankcase and pump it back to the oil tank.

The integrated dry-sump system is so precise at monitoring oil levels that the engines have no engine oil dipstick. Instead, an electronic monitor measures the oil level and displays the result on the instrument cluster.

Únique VarioCam Plus
The valves are precisely engineered for minimum tolerance and interact with cup tappets also optimized for minimum weight and feature hydraulic valve play compensation. To ensure valve operation, even at high engine speeds, both the intake and exhaust valves feature double valve springs. Both intake and exhaust camshafts are hollow to further reduce weight. All intake and exhaust ports are polished for optimum flow characteristics.

As with other 911 Carrera engines, the powerplant in the 3.6-liter GT3 and GT3 RS has Porsche VarioCam Plus system to adjust intake valve timing and lift.

This adjustment relies on a vane-cell adjuster, similar to the one used in the current 911 Carrera. The range of camshaft adjustment is 52 degrees, up from the pervious 45 degrees. The intake camshafts also have increased valve opening by 0.4 mm over the previous model. Total intake valve opening is now .49 inch (12.7 mm) for improved engine breathing at high speeds. Exahust valve stroke of .44 inch (11.1 mm) remains unchanged, as do the cam lobes' contours.

Variable length intake manifold
The intake charge for each cylinder is optimized at all engine speeds thanks to a new variable intake manifold with two switchable resonance flaps. The manifold is made of aluminum to ensure the manifold's strength and the precision of its complicated geometry.

Boasting large-diameter cross sections with smooth internal surfaces, the manifold flows extremely efficiently. The air collectors and intake runners are all carefully finished for optimum smoothness and feature extra-large dimensions.

Large and small switchable connection pipes allow the effective length of the manifold to change for optimum resonance pulsing. A multistage intake system with several resonance flaps under the control of the engine's Motronic® engine control module ensures a smooth and consistent torque curve. The engine has a carefully mapped switching strategy for the flaps controlling the resonance pulses of the intake charge.

Both flaps remain closed at low and medium engine speeds. The first resonance flap opens at approximately 5400 rpm, exposing the small connection pipe in the process. The small pipe closes at approximately 6350 rpm and the second resonance flap opens up the large connection pipe. This intelligent management of the system ensures a muscular torque curve throughout a wide engine-speed range, and helps maximize engine power.

Keeping the cats close
Porsche engineers designed a totally new exhaust system for the GT3 and GT3 RS to ensure an optimized charge cycle. The exhaust gases flow initially through two fan-type manifolds which have the advantages of low flow resistance and an improved mixing effect. This helps to improve treatment of raw emissions before the exhaust even reaches the catalysts.

The catalytic converters on the GT3 and GT3 RS are behind the manifolds. In fact, the exhaust manifold and catalyst housing form a common unit. The catalysts so close to the engine serves to warm up the catalysts more quickly, ensuring a rapid response and thus reducing exhaust emissions particularly when starting the engine cold. As a result, the cars meet both the current Euro 4 as well as the federal LEV-II emission standards. ( posted on conceptcarz.com)

After leaving the catalysts, the exhaust flows into two pre-mufflers controlled by the engine's map control system. This control function incorporates two flaps downstream of the catalytic converters which can guide exhaust gases either into the pre-mufflers or directly into the main muffler beneath the rear end of the car. Once the exhaust gas flaps open, they provide a direct link to the main muffler and exhaust gas back-pressure decreases by approximately eight percent compared with the previous GT3.

The exhaust gas flaps are controlled as a function of both load and engine speed. The flaps are closed when starting the engine, but open as soon as the driver calls for more power. Whether the flaps are open or closed, the GT3 and GT3 RS meet all noise standards. ( posted on conceptcarz.com)

This exhaust system is 12 liters larger in capacity than the one on the previous model, which means lower exhaust gas back-pressure and more power. At the same time, the new exhaust is significantly lighter than the one it replaced. The weight savings is thanks to the system's singleshell, weight-optimized structure, with thinner walls incorporating reinforcement ribs and arched sections for greater strength.

Finally, the new exhaust configuration results in the characteristic rumbling sound of a truly sonorous six-cylinder.

Six-speed gearbox with shift-up display
As befits a purist's race car, the GT3 and GT3 RS come only with a manual gearbox. The gear ratios of this six-speed transmission are specially matched to the engine's torque curve. The ratios of Second through Sixth gears are shorter than in the previous model's transmission, for better acceleration.

As an aid to optimum performance, a shift-up display illuminates in the tachometer shortly before the engine reaches its shift point. In consideration of driver-response time, the display illuminates sooner in lower gears than in upper gears. When the driver approaches maximum engine speeds in the higher gears, this visual signal is even closer to the engine's cut-off speed. The overall shifting ratio on the gearbox is 15 percent shorter than on the previous model and 22 percent shorter than on current 911 Carrera models. Given the serious racer's need to vary gear ratios for different race tracks, the GT3 and GT3 RS transmission ratios may be varied by exchanging gearsets. This option is intended exclusively for race track use only, not for public road use.

Sport Chrono Package Plus optional
Available options include Chrono Package Plus that records lap times and other information. Other available options include Porsche Communication Management (PCM) with navigation system. The navigation module allows rapid

Source - Porsche