It seems that the ‘on-paper’ superiority of BMW’s M135i xDrive is about to receive a serious challenge from Audi’s all-new S3, due to be launched at the forthcoming Paris Motor Show.

Based upon the new lighter Audi A3, the 2013 S3 weighs 60kg less than its predecessor, tipping the scales at just 1,395kg. And while the S3 Sportback previously wielded 261bhp, its successor deploys a class-leading 296bhp from a completely new 2.0 TFSI engine, developed specifically for the S3.

BMW’s M135i offers 315bhp from its 3-litre turbocharged engine, but also weighs 120kg more than the S3.

Audi A3 Sportback
New Audi A3 Sportback

There’s a new A3 Sportback appearing in Paris next week, which is likely to receive the new S3 engine or a future RS engine to replace the current RS 3 Sportback.

The more family-oriented A3 Sportback five-door has a longer wheelbase than its predecessor and three-door counterpart, offering even more space and versatility. It goes on sale in the UK priced from £19,825 for the 120bhp 1.4 TFSI model.

Audi A3 Sportback

* * *

Despite its identical 1,984 cc displacement, Audi’s 2.0 TFSI engine is completely new from the ground up. The four-cylinder unit delivers 296bhp at 5,500 rpm and 280lb-ft (380Nm) of torque between 1,800 and 5,500 rpm. Unusually for a turbocharged engine, the S3 revs up to 6,800 rpm providing a broad spread of usable performance.

Performance is significantly better than the outgoing model, with zero to 62mph achieved in 5.1 seconds when fitted with the optional S tronic transmission, or 5.4 seconds with the standard manual transmission. Top speed is electronically governed at 155mph.

Combined fuel economy stands at 40.9mpg with S tronic (or 40.4mpg with the manual transmission), corresponding to CO2 emissions of 159g/km (162g/km for the manual).

The outgoing S3 covered the same zero to 62mph increment, some 0.5 seconds slower (5.6 seconds with S tronic), achieving 33.6 mpg and 195g/km of CO2 emissions.

* * *

The new engine is more than just a powerhouse, it features two balancer shafts rotating at twice the speed of the crankshaft delivering impressive levels of smoothness for a four-cylinder unit, and produced a sporting engine note with the aid of an electromechanical sound actuator at the bulkhead. The exhaust system uses a sound flap, that opens at certain engine speed ranges, to give the S3 an even more purposeful soundtrack.

Nearly 300bhp is an impressive output from a 2.0-litre engine, which can be partly explained by the S3’s unusually high compression ratio of 9.3:1 for a turbocharged engine.

The S3’s powerplant also features a larger turbocharger than its predecessor, achieving a maximum boost pressure of up to 1.2 bar. Combined with a clever combustion system which uses indirect injection, the engine no longer requires full-load enrichment during sporty driving, hence reducing fuel consumption and emissions.

Despite its complexity and high output, the new 2.0 TFSI weighs just 148kg – more than 5kg less than the previous engine.

As before, the S3 comes fitted with Audi’s quattro all-wheel drive transmission as standard. This uses an electronically controlled and hydraulically actuated multi-plate clutch, located at the end of the prop shaft, just in front of the rear axle differential.

During normal driving, the engine’s power is delivered to the front wheels, but the multi-plate clutch can transfer torque steplessly to the rear axle in just a few milliseconds.

Chassis, Steering and Braking system

As with the engine and body shell, Audi has managed to remove weight from the S3’s chassis to offer a more responsive and agile driving experience.

The front axle has been shifted forward by 52mm compared with the previous S3, while the 5kg lighter 2.0 TFSI engine is tilted backward by 12 degrees.

The subframe, pivot bearings in the McPherson front axle, rear wheel carriers, crash management system, front wings and bonnet are all made of aluminium, saving a further 17kgs of weight.

The S3 features a new progressive steering system, which is geared in such a way that the ratio varies – being somewhat indirect around the centre and very direct when steered sharply. Audi assures us this provides for a pleasantly smooth character when driving straight ahead and rapid response in tight corners, but it’s worth checking this out for yourself before you opt to buy it.

The S3 runs on 7.5 x 18″ five-spoke alloy wheels in S-specific design, fitted with 225/40 tyres, which are lighter yet stronger due to a new flow forming production approach.

Braking is provided by vented discs – 340mm at the front – clamped by black calipers emblazoned with S3 logos. A new electromechanical parking brake, which the driver operates via a button, is integrated into the rear axle brake system.

An updated ‘magnetic ride’ electromagnetic damper control system is fitted, which constantly analyses the condition of the road and the driver’s style, repeatedly adapting the damper forces within milliseconds. The driver can choose between three modes, including normal and sport. These are fully integrated into Audi’s drive select system and simultaneously alter the S3’s steering response.

Uk prices have yet to be announced, however Audi has confirmed that the new S3 will cost EUR 38,900 in Germany when order books open later in 2012.

This compares with the price of the outgoing S3 Sportback which retailed at EUR 39,050, so we would expect the new S3 to cost around the same as its predecessor – £31,840 – here in the UK.

How do they compare? – All-new Audi S3 vs BMW M135i xDrive

Audi S3 vs BMW M135i xDrive

Engine 1,984cc four cylinder TFSI 2,979cc six cylinder
Transmission 6-speed S tronic 8-speed sport automatic
Max. power 296bhp 315bhp
Max. torque 280lb-ft (380 Nm) from 1,800 to 5,500 rpm 332lb-ft (450 Nm) from 1,300 to 4,500 rpm
Unladen weight(kg)* 1,395 kg 1,515 kg
Top Speed (mph)** 155 mph 156 mph
0-62mph acceleration (secs) 5.1 seconds 4.7 seconds
CO2 emissions (g/km) 159 g/km 182 g/km
Fuel consumption (mpg) 40.9 mpg 36.2 mpg
Price (£)*** EUR 38,900 (for 6-speed manual)
(£31,840 for outgoing S3 Sportback.)
EUR 44,000 with 8-speed auto
(£29,995 for M135i RWD – EUR 39,850)
‘Benefit-in-Kind’ (BIK)**** 21% 26%
* Unladen weight less 75kg for driver and luggage (Directive 80/1268/EEC).
** Top Speed limited.
*** M135i xDrive is only available in Europe – the ‘£’ price refers to the rear-wheel drive M135i which retails at 10% less than the M135i xDrive.
**** Benefit-in-Kind (BIK) is the percentage of the total value of a company car which is taxable, based on its CO2 emissions.

* * *