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Audi R8 e-tron prototype review: 4.0/5

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We drive the R8 e-tron electric supercar, a car that Audi will not sell you. Seems pointless: it isn’t!

Paul Healy

Words: - @P_aulHealy

Published on: June 11, 2013

Words: - @P_aulHealy

Published on: June 11, 2013

Tech Specs

Model testedAudi R8 e-tron prototype
'Engine'twin permanent magnet electric motors, 48.6kWh Li-ion battery pack
Transmissionsingle-speed automatic, rear-wheel drive
Body styletwo-door coupé
Top speed200km/h (limited)
0-100km/h4.0 seconds
Power381hp
Torque820Nm

The experience of drifting an all-electric supercar around a disused East German airfield is tempered by the knowledge that the car said drifting was completed in will not make it to production. However, this is one of those cases in which the sum of the parts is greater than the car. The technology derived from the R8 e-tron will, in time, make their way into mainstream Audi models you can actually buy.

In the Metal:

While the looks of the R8 e-tron are undeniably familiar, the car actually shares very little with its petrol powered namesake. There are just nine components common between the two cars as the e-tron was built from the ground up to be an electric car rather than just shoehorning electric components into a car designed for a combustion engine. Much of the changes relate to 'adding' lightness, with the chassis constructed predominantly from aluminium and carbon fibre reinforced plastic (CFRP). On top of this, CFRP body parts are hung, all optimised for cooling, drag or some other parameter. Even the rear hatch, which would ordinarily house a glass cover through which you can view the engine, has been replaced with carbon fibre. This does mean that you cannot see out, but a rear view camera borrowed from the R18 Le Mans winner works with a TV screen in place of a rear view mirror to deliver dazzle proof video.

Weight saving goes beyond just cladding the car in CFRP; the springs are also made of the lightweight material and skim valuable kilograms from the kerb weight. As too do the wheel hubs hewn from titanium and even the unique Continental tyres. All told the body comes in at a shade under 199kg; that's important when you realise that the battery system weights 575kg.

Made up of 389 liquid cooled lithium-ion cells the battery is located between the axles in a T shape, running along the centre tunnel and into a carbon fibre bulkhead that would usually house a V10 petrol engine. Mounted as low as possible the batteries power a pair of electric motors located over the rear axle.

Driving it:

Unlike regular R8 models, and indeed previous iterations of the R8 e-tron, which feed their power to the wheels via quattro all-wheel drive, the current car is just rear-wheel drive. The complexities and added weight associated with all-wheel drive were deemed not to add a performance benefit and so it was binned. This may seem at odds with a company that prides itself with the surefootedness that quattro brings but Audi has countered this with an advanced torque-vectoring system that is claimed makes up for it being 'only' two-wheel drive.

With each rear wheel being independently powered the system can brake or accelerate either side to keep things in check at all times. Once it is engaged that is; in efficiency mode the system is idle and there is a degree of understeer through tighter corners, but move the Drive Select system to Auto or Dynamic and the torque vectoring comes alive - allowing a degree of slip before throttling back the inside wheel and powering the outside one to pull the car straight. Dynamic mode loosens the restraint a little more meaning you can accomplish some tasty drifts - a surreal feeling in a fully electric car.

On paper the electric motors produce a combined torque figure of 820Nm. However, due to a 1:6 planetary gear design of the single-speed transmission this translates to 5,000Nm of torque. Or so the Audi engineers say; we take that figure with a huge pinch of salt as such output would likely reduce the specially developed Continental tyres and the tarmac below them to their component parts, while you pop a wheelie.

Torque figures aside the R8 e-tron does move away from the line with an immediate urgency; 0-100km/h is dispatched in four seconds flat. It is not a silent sprint either; Audi engineers and acoustic experts spent a lot of time creating a noise befitting an electric supercar and the result would not seem of place on board the Starship Enterprise. It still remains an alien sound and certainly not one you expect to hear from a car that looks so familiar but it does suit the car's high tech nature.

What you get for your Money:

Not an awful lot, as Audi will not sell you one. Despite having invested millions of Euros and countless hours into the development of the electric R8, Audi cannot make a case for it being economically viable. Unwilling to do a Bugatti and lose money on each car produced just for the kudos or ask buyers of regular Audi models to effectively subsidise this plaything for the rich, the program has been pulled.

The ten cars that have been built will now be used as test beds for future Audi electric models with the likes of the fly-by wire braking system and torque vectoring capabilities making their way to conventional Audis in time. Shame that...

Worth Noting

There is no physical connection between the brake pedal and the rear brakes on the R8 e-tron, as the system instead operates via 'brake-by wire' with an electro-mechanical brake. This is the first car the system has been introduced on and includes three separate operating modes. The friction operation of the six-pot calipers clamping down on carbon ceramic discs is joined by a recuperation system that harnesses energy used under braking to recharge the battery. The final stage is torque vectoring with the e-tron's banks of computers braking the inside wheel while cornering to ensure the car's line stays true. A separate ECU decides which mode is going to be selected at any given time and can switch between modes in what Audi calls 'Brake Blending'.

Summary

The theory and implementation of the Audi R8 e-tron have to be applauded, as too does the decision to cancel the project. Audi could have easily continued with the R8 e-tron, entering limited production for the uber rich, but it would have been a folly. Instead the technologies that have already been derived from the project, and those that the test cars turn up in future, will make their way to more mainstream production models. There is always the possibility of a range-extended rather than pure electric version, but that will likely depend on the success of the BMW i8. Audi already has the range-extending technology, as we saw last year with the A1 e-tron, so maybe this will not be the last time we see the R8...



Tech Specs

Model testedAudi R8 e-tron prototype
'Engine'twin permanent magnet electric motors, 48.6kWh Li-ion battery pack
Transmissionsingle-speed automatic, rear-wheel drive
Body styletwo-door coupé
Top speed200km/h (limited)
0-100km/h4.0 seconds
Power381hp
Torque820Nm