Audi introduced a redesigned A4 in late 2004, now riding on the B7 platform, which is completely unique to Audi and not shared with Volkswagen. Nonetheless, the B7 is really a revision of the outgoing B6, and not a ground-up redesign. This is confirmed by Audi's internal platform nomenclature, which uses PL46 (longitudinal passenger car platform, size 4, generation 6) for both B6 and B7 chassis.
The engine lineup received many additions, the most notable of which was the introduction of Fuel Stratified Injection on the new 2.0 TFSI and 3.2 V6 FSI, respectively capable of 200 and 255 PS (147 and 188 kW), although these engines dropped the five-valve design in favor of the more widely known four valves per cylinder configuration, as the design was incompatible with the direct injection system. The new 2.0 TDI engine now combined Pumpe Düse (PD) technology with 16 valves for the first time, while the larger 2.5 TDI was increased to 3.0 L, with 204 PS (150 kW). quattro was available either as an option or standard on most mid- to high-end models, with multitronic and Tiptronic automatic gearboxes available throughout the entire lineup. As per the B6, multitronic is available only on front-wheel drive models and Tiptronic only available on quattro models.