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Audi’s monumental 4 500Nm E-tron

2009-09-16 10:37
Vehicle Specs
Manufacturer Audi
Model E-tron
Engine Four motor electric
Power 230kW
Torque 4 500Nm
Zero To Hundred 4.8
Top Speed 200km/h (limited)
Weight 1 600kg
Tyres F: 235/35 R: 295/30 R
If you though the company’s R8 Spyder was stunning, say hello to the future of Audi performance motoring – the E-tron.

In essence it’s an electric drivetrain enabled R8, with some very clever German lateral thinking. It could quite possibly be the show stopper of this year's Frankfurt motor show.

Is 4 500Nm really enough?

The headline figures produced by dual front and rear electric motors (driving one wheel each to enable authentic Quattro all-wheel electric drive) are astonishing.

Power peaks appreciably lower than a comparable entry level R8 (the E-tron peaks at 230kW), yet rotational force is apocalyptic, an astonishing peak of 4 500Nm.

Don’t expect it to best the current R8 V8’s performance figures though, despite the monumental torque figure.

Torque vectoring apportions drive to wheels on demand, factoring in steering and slip angles, which means although the default drive configuration is a 30/70 rearward bias, you’ll never see 4 500Nm deployed all at once.

A particular advantage of electric drive, in conjunction with a torque vectoring system, is the immediacy with which toque flow to individual wheels can be increased or decreased.

Parameters for dynamic stability interventions or performance driving are practically infinite with an electric drive torque vectoring system, unlike traditional limited-slip differentials.

Unlike the R8, no sideblades for E-tron. Surfacing is mostly devoid of air-intakes, as there is no engine to cool. Front air-intakes can be closed at speed to aid aerodynamic efficiency.

Plastic surfacing?

Problem is, batteries are heavy.

The E-tron’s Lithium ion battery pack weighs 470kg - a lot more than an R8's V8 engine. Battery pack positioning can play havoc with weight distribution, compromising a car's handling fluidity.

Fortunately E-tron's battery pack is mounted ahead of the rear axle, keeping the mass well centred.

Credit to Audi’s engineers then, for managing to trim E-tron’s kerb weight down to 1 600kg (not far off the current R8 V8) in a 48/52 rear bias.

Construction technologies which have offset the mass penalty of E-tron’s battery pack are Audi’s fabled aluminium space frame technology and new carbon fibre-reinforced polymer (okay, plastic) body panels.

In terms of performance E-tron shadows R8 V8 with regards to acceleration (only 0.2 sec slower from 0-100km/h in 4.8 seconds) yet is severely curtailed at the top end with a 200km/h limiter.

Tractability is excellent though, with 60-120km/h dispatched in only 4.1 seconds.

Simple recharging

Sporting electric drive, range and recharging are important factors to consider – usually being the Achilles heel of most contemporary electric vehicle designs.

For E-tron, Audi claims effective range of 247km, with maximum capacity charging possible in 6-8 hours from a stock household socket – EU spec though, 230V.

If you have access to a 400V outlet, it cuts recharging time to only two and a half hours.

From a production point of view, the E-tron appears to be pure conceptual grandstanding - or is it?

Audi is about to set a serious e-performance project in motion commencing this October, with the aim of realising a performance orientated production electric drive system within three years.

Bosch will be a major technology partner in this venture, so only a fool would bet against seamlessly integrated Audi electric drive by 2012.


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