SPY PICS: New Audi S4, Avant snapped

Spy photographers on the prowl at the world's most famous road-circuit, the Nurburgring Nordschleife, have snapped the next-generation Audi S4 sedan and wagon undergoing testing.

The new images are revealing in many ways, showing subtle tweaks to Audi's most important car, including a new take on its angular headlights and now trademark LED driving lights. The new LED design for the S4 models features a secondary, lower light bar and together with a slightly wider stance and a reworked front fascia the new models are expected to command plenty of attention on the road.

Clearly Audi is sticking to its tried-and-tested design with the new A4, which will still be instantly recognisable, with evolutionary design tweaks rather than wholesale changes, although the brake lights appear to adopt a more angular, wedge-shaped motif.

In Australia, the Audi S4 models are currently priced at $105,000 and $108,500 for the sedan and wagon respectively, which will be replaced by the vehicles spied in Germany in 2016, after an expected reveal at the 2015 Frankfurt motor show in September.

Codenamed 'B9', the fifth-generation A4 will be slightly longer and wider than before to deliver more interior room, and will be based on the new MLB2 platform as previously reported.

The updated platform will see the car adopt new technologies, including electric 'e-tron' capabilities, and should see it shed significant weight.

A range of engines will be offered, catering for all types of customers including those who want to save money on fuel bills, and those who want more power – as is the case with the S4 models.

Currently the Audi S4 cars are powered by a 3.0-litre supercharged V6 and 245kW/440Nm, but Automedia suggests a less powerful 2.0-litre turbo with around 155kW will be added to the range, potentially offering a model priced around the $85,000 mark.