THE 1988 TRANS AM CHAMPIONSHIP

11 Jan 2015 | Author: | Comments Off on THE 1988 TRANS AM CHAMPIONSHIP
Audi 100

THE 1988 TRANS AM CHAMPIONSHIP

First held in 1966, the Trans-Am series is the oldest motorsport championship in the Unite States and continues to gain in popularity from one year to the next. 176,000 spectators saw the TransAm race at the 1987 Detroit Grand Prix and 136,000 fans came to the final round of the season in St. Petersburg.

This wide interest can probably be attributed to the fact that only cars with a production volume of at least 1,000 per year qualify for the championship.

The races are held on asphalt circuits in both the USA and in Canada. The circuits are not all specially built for this purpose: in many cases normal city streets are converted into racing circuits, as in Detroit or Dallas for example.

A very flexible set of regulations introduced in 1980 permits a generous amount of elbow room for changes to the bodyshell, running gear, engine and transmission. Under these rules the Sports Car Club of America (SCCA) also specifies a starting weight for each of the competing cars. Restrictions can be imposed at any time on the best-performing cars, for instance, additional weight, air restrictors or narrower tires so that the races do not become predictable.

The first TransAm champion was Jochen Rindt (the Austrian who later became Formula 1 World Champion) driving an Alfa Romeo. From 1967 onwards, however, American products took the limelight, as had initially been planned. Eight cylinder engines with over 600 bhp dominated the series. Foreign makes very rarely had serious chances.

Racing team managers such as Roger Penske and Dan Gurney entered well know drivers for the championship, with support from the manufacturers. And so the TransAm series became popular with the public.

After an initial popularity peak in 1970, the TransAm suffered its first decline. In fact, all kinds of motorsports were suffering the effects of the oil crises.

But with the introduction of new regulations, the TransAm was brought to life again. The old rivalry between Ford and Chevrolet started where it had left off. And non-American car manufacturers, Nissan became a potential winner. new impetus was provided for the 1988 TransAm season: Hurley Haywood, Walter Rohrl and Hans-Joachim Stuck competed with the Audi 200 quattro, which was received with sceptical smiles and not credited with any serious chances by the Americans at the start of the season. This was however soon to change!

THE DEVELOPMENT OF THE TRANS AM AUDI 200 QUATTRO

We’ve got something to prove, and we intend to prove it promised Joseph Hoppen manager of Audi of America Sport Department, before the start of the season.

And that’s what happened. Before the first appearance of the four wheel drive Audi quattros at Long Beach in California, the formula for winning the Trans Am was quite simple: the competition cars, based on a tubular steel frame chassis and fitted with he most powerful engine possible and a fiberglass bodyshell were given the most up to date technology and sent to the starting line.

Audi chose a different course, Herwart Kreiner and his motorsport department had only a couple of months time to develop a competition car. Three Audi 200 quattros had to be constructed within a very short period, as the decision to participate in the US series was taken at a very late stage.

On the basis of a standard Audi 200 quattro, a competition car was prepared with bout 510 bhp derived from the standard production 5 cylinder turbo engine, modified competition running gear and a bodyshell with enhanced aerodynamics.

Audis main consideration in developing the car was the four wheel drive power train. No four wheel driven car had ever competed in the TransAm championship previously. Rear wheel drive and very powerful engines were the order of the day: but of course a powerful engine is not much use if its power is not applied to the best effect.

The decisive factor here is therefore not pure power, but the most efficient way to distribute the power to the four wheels.

The Audi engineers were able to draw on their past experience in rallying which was revolutionized in 1981 with the first appearance of the four wheel drive Audi quattro.

THE BODYSHELL

Compared to European standards, American motorsport regulations are very liberal. So the engineers have a relatively large amount of scope when developing the bodyshell for a competition car. Only the cars side profile has to correspond to the production car dimensions.

Front and rear spoiler are not included in this measurement.

The Audi engineers took the monocoque bodyshell of the production version Audi quattro as the basis for the TransAm competition car. Thy had already gathered positive experience with the Nardo High speed record car developed in the Neckarsulm plant and with the Audi 200 quattro Group A rally car. Both vehicles were based on the standard production bodyshell.

For the new demands of circuit racing, several requirements had to be met by the new vehicle.

Maximum accident protection for the driver

Optimum handling behavior

Best possible aerodynamics

A tubular steel cage was welded into a composite structure bodyshell with a special lateral impact protection for the drivers safety.

Additional stiffening was required for the running gear in order to cope with the high cornering stresses, and optimum handling response was achieved by modifying the geometry of the suspension take up points.

Aerodynamics and handling played key functions in determining the design of the bodyshell. The aerodynamics, among other things, determined the cars’s maximum speed, while the downforce at the front and rear wheels influenced handling and maximum cornering speeds.

Numerous wind tunnel tests and road trials were necessary to achieve the correct dimensions and values.

The drivers seat for example was moved 40cm (15.75 inches) towards the rear to improve weight distribution at the rear axle. A series of aerodynamic improvements, including the front and rear spoilers, ensured that the bodyshell had minimum drag combined with the best possible downforce effects.

DRIVELINE AND RUNNING GEAR

The American regulations allow extensive modifications to the driveline as well as the body. For example, the complete engine can be moved rearward to improve the weight distribution. In spite of the available possibilities, the Audi engineers kept to the original quattro formula with the engine in front of the front wheels, a center differential integrated in the transmission and the drive taken to the front through a hollow transmission shaft.

For circuit racing the TransAm car was equipped with a modified, fully synchronized 6 speed manual transmission, similar to the one used successfully in the Audi Sport quattro S1.

To improve torque distribution on the race track, the front differential is controlled by a viscous coupling, and the rear differential has a self-locking multi-plate clutch pack.

The car has a choice of two center differentials, given different front/rear torque split characteristics to suit the requirement of the different circuits. One of these is a fully automatic Torsen unit, and the other employs epicyclic gearing with an integral viscous coupling that varies the instantaneous torque split and braking effect independently.

Audi main advantage over the competition, and a major factor in the development of the TransAm Audi 200 quattro was the Audi running gear with the quattro drive line.

Although the suspension components are completely free under US regulations, the race car retains the standard suspension layout of the Audi 200 quattro, with McPherson struts at the front and double transverse links at the rear.

Ground clearance was reduced to 65mm. With a total suspension travel of 50mm, this meant shortening the super progressive steel springs and reducing the stroke of the twin tube shock absorbers.

The car uses the brake system of the Audi Sport quattro S1, except that the front end and rear discs had to have the same diameter due to the 50:50 weight distribution.

THE ENGINE

SCCA homologation rules and a power requirement of at least 500 bhp determined the choice of the well proven 5 cylinder 2 valve engine of the standard production Audi 200 quattro as the base engine for the TransAm car.

However a number of modifications were necessary to bring up the power level and ensure race durability. The power unit was given an aluminum crankcase, modified combustion chambers and bigger inlet and exhaust valves.

To improve the weight distribution, the alternator was relocated to the back of the passenger compartment, where it si driven directly off the rear drive line.

A second fuel pump was necessary to fee the race tune engine with sufficient fuel.

As further measure, the boost pressure was raised from the standard 1.7 bar to 3.0 bar, which again involved a number of engine modifications. Special materials were needed to withstand the higher stresses resulting from the increased boost pressure.

As well as the aluminum crankcase, the engine has a magnesium oil pan, mimonic exhaust valves and a gas-nitrided camshaft and crankshaft. The exhaust manifold and intercooler were also modified accordingly for race conditions.

TECHNICAL SPECIFICATIONS: THE TRANSAM AUDI 200 QUATTRO

Turbocharged 5 cylinder aluminum in line:

Installed: Longitudinally, front, angled 27.30 degrees to the right

Capacity: 2110 cc

Bore and Stroke 79.5 X 85mm

Valves: 2 valves per cylinder

Power: 510 bhp (375kW) at 7500 RPM (increased to 550 bhp during the season)

Torque: 530Nm at 6,000 RPM

Turbocharger: KKK turbocharger with intercooler

Fuel System: BOsch Motronic

Ignition System: Bosch Motronic

Spark Plugs: Bosch with platinum electrode

Lubrication: Dry sump with Shell TMO oil

PERMANENT FOUR WHEEL DRIVE

Clutch: Dual plate dry clutch

Transmission: All synchromesh 6 speed manual transmission

Center Differential: Self locking Torsen, or limited slip viscous coupling with torque split function

Front Differential: Limited slip viscous coupling

Rear differential: limited slip friction plate differential or Torsen self locking differential, or limited slip viscous coupling

Drive Shafts: Constant velocity sliding joint shafts

ALL INDEPENDENT SUSPENSION

Suspension: As on Audi 200 quattro standard version: Front: McPherson struts with bottom track control arms. Rear Trapezium arm suspension

Shock Absorbers: Boge twin tube cartridges

Steering: Rack and pinion, power assisted, ratio 14:1

Rims: 12X16

Tyres: 25.5X13.5X16 (fry) Goodyear, 25.5X12X16 (rain) Goodyear

BRAKES: HYDRAULIC TWIN CIRCUIT SYSTEM

Components: ventilated discs (330mm dia X 32mm Front/304mm Dia X28mm rear, light alloy calipers

Brake Balance: manually adjustable by driver

Brake Cooling: Ram air cooling

Pad Material: Asbestos free

BODY: Based on Audi 200 quattro, plastic skin panels

Equipment:

Safety equipment: Steel cage welded to bodyshell, 6 point safety harness, fire extinguisher system, rubber safety tank.

Length/Width/Height: 4,897/2,033/1,340mm

Wheelbase: 2,687.5mm

Track, front/rear: 1,620/1620mm

Curb Weight: 1,115kg (increased during the season to 1202kg with additional weights.

Oil capacity: 12 litre s, water 8 litres

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