Audi’s V10-engined R8 has been extensively revised to produce a lighter, more powerful limited edition model. The R8 GT loses 100kg and gains 35PS compared with its stablemate. If that sounds good you’d better be quick, because only 33 cars will be made available to British buyers.
The R8 is built using an aluminium spaceframe, so weight-saving measures have necessarily been many and small, using lessons learned from the R8 LMS GT3 racer. The body of the standard car weighs 210kg; Audi has not stated a body-in-white mass for the GT version, but some of the weight savings have come from elements of the bodyshell.
Audi R8 GT.
At risk of delivering a dull shopping-list, here is an account of where the savings in weight were made.
Lighter sheet metal and additional cutouts knocked 2.6kg from the mass of the aluminium ‘boot lid’ covering the 100-litre luggage compartment at the front. At the rear, the speed-activated rear spoiler has been replaced with a fixed wing, saving 1.2kg.
The carbon fibre reinforced plastic (CFRP) engine cover is 6.6kg lighter than its aluminium equivalent; the use of CFRP for the rear bumper and sideblades saved 5.2kg and 1.5kg respectively.
Thinner windscreen glass, and the use of polycarbonate for the bulkhead and the window in the rear hatch, have together saved 9kg.
Several mechanical components have been replaced with lighter items. The braking system is, by methods unspecified, a kilo lighter; 4kg has gone from from the aluminium caps of the brake discs; the battery is 9.4kg lighter; the GT’s air intake module weighs 2.3kg less than the standard item; and the insulation of the engine compartment has been cut back, saving 2.8kg.
The R8’s interior has also been rethought in the interest of weight-saving. The main result is new bucket seats with GRP chassis: these save 31.5kg over the normal fully-adjustable items. Lightweight carpeting has been adopted, sparing 7.9kg.
Altogether, this piecemeal whittling process has brought the kerb mass down to 1525kg.
Breathing improvements to the 5204cc V10 have led to a 35PS gain in maximum power, which now stands at 560PS — the speed at which this is delivered is not stated, though the standard car peaks at 8000rpm. The peak torque of 540Nm arrives at a lively 6500rpm. The rev limit is set at 8700rpm.
The claimed maximum speed has improved modestly from 196mph to 199mph, while 100km/h is reached from rest in 3.6s instead of 3.9s. These gains are certainly
something of an anticlimax, particularly given how quick the standard car already is, but the 100kg lost from the kerb mass will undoubtedly help with handling agility — of which more anon.
The R8 GT comes fitted with Audi’s sequential six-speed ‘R-tronic’ transmission; the fully manual box isn’t available. Gearchanges at high loads and crankshaft speeds take one tenth of a second; normal, sport and manual modes are available.
Like the normal R8, the GT drives all four wheels. The Quattro system’s centre differential is a viscous coupling mounted behind the front differential; during normal driving, it sends 15 per cent. of the driving torque to the front wheels. Driven hard, this achieves the desired mild oversteer with the R8 GT’s 43:57 per cent. front:rear weight distribution. The coupling can direct up to 30 per cent. of the torque to the front wheels if rear slip angles start to build.
A mechanical locking differential is fitted at the rear axle: it provides up to 25 per cent. lock-up when accelerating, and up to 40 per cent. on the overrun.
Changes to the R8’s running gear make a better case for the GT than the extra power and leaner kerb mass ever could by themselves. The rack ratio of the Audi’s power steering system has been tightened from 17.3:1 to 16.3:1. Higher (that is, more negative) front and rear camber angles give better turn-in and bite; and the coil-over suspension is manually adjustable, allowing the ride-height to be dropped by up to 10mm. Wheel location is by double wishbones front and rear, so the basics are right already.
The A8 GT’s stability system has a sport mode, which allows a little more oversteer to develop before it intervenes; the system can also be switched off. Special forged 19-inch wheels are standard, and Cup tyres will be available; otherwise, wheel and tyre sizes are unchanged..
The standard R8’s steel brake discs have been replaced by internally-ventilated carbon-fibre ceramic items. Apart from having good thermal properties and being very durable, they are also 9kg lighter than their steel counterparts.
A number of small aerodynamic changes have been made, aimed not only at achieving a little more downforce, but also — Audi admits — making the car look more dramatic. The most visible example of this is the fins at the corners of the nose. The Cd and frontal area (0.36 and 1.99m2) are unchanged.
Anyone who wants to race their R8 can buy Audi’s race package. This includes a bolt-in roll bar (in red or black), which has both road and track approval; road-approved four-point belts (also in red or black); a fire extinguisher; and a kill switch for the battery. You can also splash out on a front bar module for motorsport events: this includes a rotary lock for the four-point seatbelt, and turns the roll bar into a full cage.