Porsche 996 GT3 Information.
This is our tribute to the finest, every day, naturally aspirated sports car ever manufactured.
Overview:
The year 1999 saw Porsche introduce their highly anticipated, high performance version of the 911. The GT3.
The GT3, named after the FIA GT class it was intended for. The Porsche GT3 combines the style and modernity of the 996 with the RS attributes previously available with the 964 RS and 993 RS models. A highly competent engineering feat giving superb on-track performance and handling whilst enabling everyday use in relative comfort. With its specially developed high performance engine in place, the rear-wheel drive-only GT3 became the first production car to lap the fabled Nurburgring in under eight minutes.
In 1999, Porsche's official test-driver Walter Rohrl completed the Nurburgring Nordschleife with the 996 GT3 in 7 minutes 56 seconds. The first production car to go sub 8 minutes!
Pre-production history:
After winning the 1998 24 Hours Le Mans overall with the Porsche GT1, Porsche had announced not to enter the 1999 Le Mans with a factory car suitable to defend the overall win against the competition by major automakers due to an internal agreement with Ferdinand Piech to leave the field to the Audi R8 (Racer).
Instead, Porsche decided to focus again on less expensive GT racing classes, and began making plans to modify the new 996 generation of the 911.
They set out to develop the racecar simultaneously with a road-going variant, which was required by GT class homologation rules.
Technical statistics and features:
Many additional developments were also made.
The body was based on a Carrera 4 bodyshell. Several modifications were needed to provide space for the seperate dry sump oil tank.
The engine and transmission mounts were also modified.
To save weight the spare wheel was left out and a repair kit supplied.
External changes include a new nose and side skirts.
The ride-height being dropped by 30mm thanks to fully adjustable dampers with shorter, firmer springs and adjustable anti-roll bars.
There were also adjustable spring platforms and strengthened ball bearings. Brakes were now 330mm cross-drilled and ventilated discs all round (compared to 318mm front and 299mm rear for the standard 3.4-litre 996 Carrera), the four-piston aluminum monobloc calipers coming painted red. Lightweight 10-spoke 'GT3' wheels had an 18-inch diameter and measured 8 and 10-inches across at the front and rear respectively.
As with Porsche's 911 RS models, the GT3 was devoid of any unnecessary items that would add weight to the car. Sound deadening was almost completely removed, as were the rear seats, stereo system, sunroof, and air conditioning, although automatic air conditioning and CD/radio became no-cost optional add-ons.
To bring the vehicle's track-prowess to the maximum level, Porsche endowed the GT3 with a new front bumper with matched rear spoiler to help increase down-force, thereby increasing grip.
Engine:
All aluminum water cooled horizontally opposed flat six .
Two overhead cams per bank of wet Nakisil lined cylinders. 4 Valves per cylinder and Porsche VarioCam variable valve timing.
Variable intake manifold.
It is actually based on the original air-cooled 911's versatile, true dry-sump crankcase, with an external oil tank. In GT3 configuration, this so called "split" crankcase (meaning the parting line of crankcase is on the crankshaft centerline) uses, instead of a fan and finned cylinders, separate water jackets added onto each side of the crankcase to cool banks of 3 cylinders with water pumped though a radiator.
Thus, the GT3 engine is very similar to the completely watercooled 962 racing car's engine, which is also based on this same crankcase. The 962 differs, however, by using 6 individual cylinder heads while the GT1/GT3, like the air and water cooled Porsche 959, uses 2 cylinder heads, each covering a bank of 3 cylinders.
The GT3 engine could thus also be thought of as similar to a 959 engine, but with water-cooled cylinders.
This engine gives the GT3 a distinct racing heritage that dates back to the Porsche 904/6 of the mid-60's, up to the Carrera Cup and 997 Super Cup and RSR racing cars of today.
Meanwhile, that high performance motor was developed not from the regular 996 Carrera engine, but as a normally aspirated version of Porsche's GT1 unit, turbo-charged versions of which had been used to win outright at Le Mans in 1998.
Inside the specially prepared block are 6 unique pistons with lightweight titanium connecting rods and a finely balanced crankshaft in eight main bearings. The crankshaft, connecting rods and main bearing journals are all Plasma-Nitride hardened as in the racing engines. Compared with nitro-carbide treatment of the Carrera engine components.
This allowed the engine to rev much harder and higher than the 3.4, All this adds up to an immensely strong engine, which although limited to 7800rpm will apparently rev to 9000rpm quite safely.
Displacement of these specially built hand assembled 'GT1 engine' re-engineered for mass production was precisely 3600cc thanks to a bore and stroke of 100mm x 76.4mm. With compression upped to 11.7:1, dry-sump lubrication and re-mapped Bosch DME sequential engine management, there was an extra 60bhp over the standard 3.4-litre production motor.
With 360bhp being produced at 7200rpm, the GT3 was the most powerful normally aspirated 911 ever offered to the public.
To help keep this cool an extra high capacity oil/water heat exchanger is installed as well as a third center mounted radiator.
Dry-sump lubrication, also from the GT1 ensures adequate oil supply during the rigorous of fast cornering. The GT3 generate very high centrifugal and inertia forces when cornering and braking, specially with racing tyres, the high and flat oil tank of the dry sump lubrication system is a seperate stainless steel unit attached to the front of the engine.
Note however that whereas on air cooled models the oil was topped up with the engine running the new water cooled engines are topped up with the ignition off
Stationary high-voltage distribution, six coils, sequential injection, cylinder-selective knock control, stereo oxygen sensing, diagnostic system, overhead camshafts, Porsche VarioCam, Hydraulic valve clearance compensation. Double chamber exhaust system with two catalysts and two oxygen sensors.
Gearbox/transmission:
The transmission selection was influenced by the higher torque rating. The heavy duty gearbox selected for this application are the 6 speed manual gearbox developed from the G50/53 gearbox family of the 993 GT2 models.
The different body shell and mounting arrangements meant that the gearbox had to be completely redesigned but the shafts and gear arrangements was simular. The four satelite differential was used complete with the asymetrical mechanical 40/60 limited slip control system (non PSM). The 240mm clutch is part of the twin mass flywheel arrangement.
The GT3 shift is about 20% shorter than the standard Carrera.
Front suspension:
All the 996 have basically the same front suspension setup with a vef variations.
The front struts and rear spring and damper units are clearly defined. The variable rate springs are cylindrical and coaxial with the strut.
The ride height is adjustable on the strut body. The standard setting is 30mm lower than a Carrera.
In view of the considerable side forces generated by racing tyres the cast aluminium front wheel carriers are modified to take 80mm diameter wheel bearings and the position of the steering levers are lowered to compensate for the lowered ride height.
At the top of the front struts the rubber element of the damper rod is replaced by a Unibal spherical joint for better and more immediate damping control. This plate have two positions. One for street tyres and one for racing tyres.
The transverse link length is adjusted to set the final camber.
Tubular anti roll bars are adjustable. For road use it is set to the center hole.
Rear suspension:
Metalic sphered joints replace the rear rubber cussioned anchorage of the longitudinal links.
There is a 7 mm increase in the set point to reduce squat and dive.
Tubular anti roll bars are adjustable. For road use it is set to the second hole.
Performance:
In the end, that extra 30kg was negated by the additional power, the GT3 posting some outstanding performance figures. Top speed rose to an astonishing 187mph (301 kph), 0-60 in just 4.7 seconds. 0-100mph in 10seconds
Trim:
Aesthetically, a number of subtle aerodynamic tweaks were made, a deep wrap-around chin spoiler minimizing air flow beneath the car. Deeper side sills further enhanced the GT3's more aggressive demeanor, as did a unique two-tier adjustable rear wing featuring a Gurney flap mounted on its lower trailing edge. Inside, there were leather trimmed bucket seats and GT3 logos on the instrument facia whilst in true RS tradition, the stock Carrera's rear seats were dumped and the vacant area trimmed with carpet. Otherwise, only a couple of the luxuries you would normally find on the Carrera were missing from the GT3, air conditioning having been moved to the options list and electric mirrors deleted, power-operated windows remaining standard.
Options:
With front and side airbags, electric windows, ABS, dual mass clutch, alarm/immobilizer the Comfort models give the driver many of the now essential goodies as standard. The stereo and air-conditioning being a no cost option. The Clubsport version comes with a bolt-in roll cage, fire extinguisher, bucket seats and single mass flywheel (notice the noise when depressing the clutch whilst stationary). Emergency cut-off switches, one under the bonnet and one in front of the gear lever. These are for track use only and the external red pull loop is normally stored under the luggage compartment lid. Those customers seeking a more track-focused cabin could specify the Club Sport package as a no cost option. This highly desirable set of upgrades included a built-in roll cage, fixed back competition bucket seats trimmed in fire-proof cloth, internal and external cut-off switches and a fire extinguisher. Also installed were six-point race harnesses and an engine that featured a lightweight single mass flywheel for increased responsiveness. Lighter and faster than the regular GT3, Club Sport versions were capable of sprinting to sixty some two tenths of a second quicker although top speed remained unchanged. The racing variants are typical, 996 GT3 Club Sport, 996 GT3 RS, 996 GT3 Cup, 996 RSR, 996 GT3-R and was made available to privateer teams.
The weight problem. This must be the first 911 that in RS format did not shed but gained weight! This was as a result of the following factors. A normally aspirated homologation special, it was the based on the concept that was created by the 1972's 2.7-litre Carrera RS.The GT3 was no stripped out lightweight. The engine, derived from the Le Mans cars mated to a stronger transmission, while better suited to track use also added weight. Larger brakes, wheels and tyres further adding to the weight problem. With very limited scope for implementing practicable weight reduction on body, trim or electrics Porsche were unable to completely cancel out the increase. It weighed approx. 30kg more than the standard 996 Carrera. The extra weight was due in part to an all-new 3.6-litre engine based on the famous GT1 architecture and the introduction of the GT2 six speed gearbox. However as compensation the power to weight ratio is higher than its predecessors. Combining the power and torque characteristics of the engine, the agile and precise handling of the chassis and high braking performance provides the driver with a very competitive package. Included in the car are state-of-the-art passive safety body concept which currently account for much of the increased weight of cars throughout the industry. 
Research material-Acknowledgement to: GT3 at Wikipedia , GT3 @ www.titanic.co.uk/GT3/ and GT3@ www.qv500.com/porsche996p3.php
The Driving impressions of the 996 911 GT3
Here are some of my impressions with regards to driveability:
(You must keep in mind that this car was at it inception classified as a super car). This is the Series 1 car that has no fancy electronic 'gizmo's, only ABS brake control. It is very, very low and on the national roads one must be very selective of the roads you travel. The suspension is that of a racer and is very direct both to where you point it as well as hard in ride comfort, What comfort?, Who cares about comfort!!!!
Performance:
The GT3 is a street legal 911 racer with the normal aspirated 3.6 liter. This 360 HP car is a wild beast but still a normal driveable car due to the fact that it is not tiring to drive. This car is LOUD!!, very load!! as it has a SPORT exhaust system. This car is very quick of the mark (0-100km/h in 4.8 sec. and 0-160 in 10. sec.) and has a top speed of 187 MPH (301 KMH). It has a six-speed gearbox that changes very easy and with no real force.The car have a limited slip differential that is great for track events as the traction out of corners is optimised. This is my dream come true, Beastly magnificent.
Handling:
The GT3 is superb in this category. You can not drive this car hard and still say that it is effortless. To drive this car on the limits is Effort, Big Effort. The power is there depending on how you want to use it. Exponentially the more power the more effort. This car is wild and taking it to the limits can be costly, very costly. It is recommended that you take an advance driving coarse and take it to a skid- pad to really get to know the car's capability. On the track it is wild. The car can be driven hard and it will perform in any situation. But beware it can cost you!!!!!!
Braking ability:
The braking ability of this car is magnificent no mater what the condition. This braking system with the ABS gives you confidence to handle most Emergency situations. The four pod calipers is out of this world. Even on driving it hard on track there is no indications of any fade.
Overall:
I really enjoys my car. I use it as much as I can. If driven "civil" the fuel consumption is not to bad.
The Technical specification of the 996 GT3
Colour : Biarritz white
Engine
Engine Design: 6 cylinder horizontally opposed
Engine Installation: Rear engined
Engine Cooling system: Water cooled
Engine Type: M 96/76
Engine Displacement (cc): 3600
Engine Bore and stroke (mm): 100 x 76.4
Engine Output DIN (kW/Hp): 265/360 at 7200 RPM
Engine Maximum Torque (Nm/lb ft): 370/273 at 5000 RPM
Engine Output per litre (kW/l/hp/l): 73,6/100.0
Engine Compression ratio: 11,7:1
Valve operation and camshaft drive: Dohc, cams driven by double chain, 4 valves per cylinder,VarioCam, intake camshaft timing varies by 25 degrees
Carburation: Bosch DME, Motronic M 5.5.5, sequential multi-point manifold injection
Ignition system: Bosch DME, distributorless ignition system with six individual ignition coils
Firing order: 1-6-2-4-3-5
Engine lubrication: Dry sump system
Engine Oil Total (l): 12,5
Transmission
Drive configuration: Rear axle drive
Manual gearbox: 6 speed
Transmission type: G 96/90
Transmission Ratios
1st Gear: 3.82
2st Gear: 2.15
3st Gear: 1.56
4st Gear: 1.21
5st Gear: 0.97
6st Gear: 0.83
Reverse Gear: 2.86
Final drive ratio: 3.44
Limited slip differential diff load/deceleration %: 40/60
Body
Body design: Steel body, 2 doors, 2 seats, entirely hot dipped gavanised body, side impact protection beams in doors, flexible polyurathane front and rear bumpers with intergrated aluminium beams, front bumper with spoiler, side skirts, engine lid with spoiler lip and fixed rear wing
Suspension
Suspension, front: Individually suspended with :disconnected" light alloy wishbones, McPherson struts with coil springs, dual tube gas filled shock absorbers, anti roll bar
Suspension, rear: Idividually suspended on five wishbones per side on light alloy multi wishbone axle with LSA system (light weight, Stability, Agility), with coil springs, single tube gas filled shockabsorbers , anti roll bar
Suspension, Front: Spring rate at wheel (N/mm) : 35.0
Suspension, Rear: Spring rate at wheel (N/mm) : 65.0
Suspension, Front: Anti roll bar (tubular- dia x thickness (mm)) : 26.8 x 4
Suspension, Rear: Anti roll bar (tubular- dia x thickness (mm)) : 20.7 x 2.8
Brakes
Brakes, front (Size (mm): Ventilated and drilled discs (330x34)
Brakes, rear (Size (mm): Ventilated and drilled discs (330x28)
Brakes, front callipers : Red 4 piston fixed aluminium monoblock
Brakes, rear callipers : Red 4 piston fixed aluminium monoblock
Brakes : Bosch ABS 5.3
Wheels front : 8j x 18, with 5mm spacer
Wheels rear : 10j x 18, with 5mm spacer
Tyres front : 225/40 ZR 18
Tyres rear : 285/30 ZR 18
Electrical System
Alternator (W/A) : 1680/120
Battery (V/Ah) : 12/36
with air conditioning : 12/46
Dimensions and weight
Track, front (mm) : 1475
Track, rear (mm) : 1495
Wheelbase (mm) : 2350
Length (mm) : 4430
Width (mm) : 1765
Height (mm) : 1270
Kerb weight (kg) : 1350
Permissible gross weight (kg) : 1630
Luggage compartment (VDA(l): 110
Fuel tank capacity (l): 63 including a 10.0l reserve
Power to weight ratio (kg/kW/kg/hp): 5.09/3.75
Fuel consumption :
Fuel type : 98 RON super plus unleaded
Urban l/100km: 20,1
Highway l/100km : 8,9
Combined l/100km : 12,9
CO2 (g/km) : 320
Performance :
Acceleration 0-100 km/h (s) : 4,8
Acceleration 0-161 km/h (s) : 10,2
Maximum speed (mph/kph) : 189/302
Production totals : 1868
