AUDI is re-igniting its BMW M3 challenge with a significantly facelifted but pruned S4 range.

On sale now, the B7 A4-based sports sedan loses the six-speed manual and unique Avant station wagon variants for a single automatic four-door sedan-only model.

The latest S4 incorporates many of the detail changes that signalled the current A4 facelift from March this year.

This includes a new nose featuring Audi’s ‘single-frame’ elongated grille design, as part of an external makeover that only leaves the doors unchanged from before.

Specific to the S4 are a grid-pattern grille, a four-outlet exhaust and a bespoke body kit featuring a more prominent front bumper with larger air inlets. Four out of the nine colours on offer are also S4 exclusives.

It also offers a brake-disc wiping function as part of the new-generation swerve control program.

High-intensity discharge headlights known as ‘Xenon Plus’ are fitted. These are of the active ‘cornering’ variety.

Mock-aluminium door mirror casings, body-coloured side sills, a boot spoiler and 18-inch ‘Avus’ alloy wheels round out the S4 exterior differences.

A new design three-spoke steering wheel, four Recaro seats finished in Nappa leather facings, ‘S’ badging, carbonfibre-style trim inlays, grey instrumentation and three disparate cabin hues – black, silver or red – also set the sportier A4 sibling apart.

Unlike the M3, which manages to summon 252kW of power and 365Nm of torque from a 3.2-litre in-line six-cylinder engine, a V8 beats under the S4’s bonnet.

Essentially the same engine as before, 253kW at 7000rpm and 410Nm at 3500rpm are the new S4’s outputs, courtesy of the ‘short’ 4163cc V8 released during the old car’s reign in August 2004.

The 4.2 V8 propels the S4 to 100km/h from rest in a claimed 5.6 seconds (5.8 for the automatic), and to 200km/h 15 seconds later, on the way to a 250km/h speed-limited maximum velocity.

Requiring 98 RON premium unleaded fuel, it averages 12.4 litres per 100km while emitting 296 grams of carbon dioxide over the same distance.

Back then this engine was an all-new design espousing greater efficiency compared to the identically powerful 4172cc unit that is still found in 4.2-litre A6 and A8 V8s.

However, the S4 still falls short of its Mercedes-Benz C55 AMG rival’s segment-leading 270kW/510Nm 5.4-litre V8.

Audi’s ‘quattro’ permanent all-wheel drive system is the only drivetrain choice offered on the S4.

It distributes torque 50:50 front-to-rear with the aid of a torque-sensing (Torsen) differential of a self-locking worm gear variety.

Slippage from any wheel can result in propulsion being diverted partially or entirely to either end depending on the circumstance.

Transmitting drive is a six-speed gearbox, in either manual or driver-adaptive, two-mode Tiptronic automatic formats. The latter’s Sport feature allows for more responsive gearshifts.

It also includes paddle shifts incorporated on the multi-function steering wheel.

As with all A4s since 2001, a four-link front and trapezoidal-link rear suspension set-up underpins the S4, controlled via speed-dependent Servotronic rack-and-pinion steering.

The S4 sits 20mm lower than ordinary A4s, on 18-inch alloy wheels shod with 235/40R18 Y-rated tyres.

Anti-lock brakes with electronic brake-force distribution are standard.

Their ventilated discs measure 345mm at the front, while the 300mm rears are high performance TRW CII-41 floating-calliper brakes. They are assisted by a dual-rate servo that automatically increases the servo rate during very hard braking manoeuvres.

On the safety front all S4s are equipped with the latest version of the ESP electronic stabilisation program (8.0).

It includes a brake-disc wiping function to keep fluid and other foreign particles from compromising stopping performance.

Dual front airbags with two-stage activation, seatback-sited front side airbags and window airbags are also part of the S4 package, along with rain-sensing wipers, an auto-dimming rear-vision mirror and new anti-whiplash front-seat head restraint.

A choice of two sunroofs (regular or solar-powered), BOSE audio speakers, a seat and exterior-mirror memory function, a DVD navigation system with TV, an electric sunblind and a mobile phone preparation are all options.

Audi is seeking 100 S4 buyers per year in Australia. It already outsells it compatriot competition in Germany, France, Spain, Sweden and Italy.

The Avant wagon, released at the time of the S4’s V8 upgrade in August 2004, has been discontinued in Australia due to a lack of demand.

Next April the RS4 arrives, bringing a significant jump in performance as well as price for the A4 range-topper.

Building on the 1705kg S4, the 1650kg RS4’s 4.2-litre V8 belts out 309kW at 7800rpm and 430Nm at 5500rpm, enabling it to hit 100km/h in a claimed 4.8 seconds and 200km/h in 16.6 seconds.

This time a six-speed manual gearbox will be the only transmission on offer. It will be followed later in ’06 by an Avant version.

The B7 S4 is the fourth Audi to wear the S4 moniker in Australia.

Confusingly the first, from July 1993 to early 1995, was based on the C4 100 (A6) sedan. It offered 169kW/350Nm from a turbocharged 2.2-litre in-line five-cylinder engine mated to a six-speed manual gearbox driving all four wheels.

The original (B5) A4 sired the S4 in 1999. That produced 195kW and 400Nm from a 2.7-litre twin-turbocharged V6. The aforementioned B6 S4 followed it in December 2003.

The price for the 2006 Audi S4 sedan is $131,200 - up $4200.