Audi S4 C4 UrS4

Audi S4 C4 UrS4

The Audi S4, produced from 1992 to 1994 on the C4 platform, holds a special place in Audi's performance history as the company's first true sports sedan. Known universally among enthusiasts as the UrS4 — 'Ur' being the German prefix meaning 'original' — this unassuming executive sedan combined Audi's legendary 20-valve turbocharged five-cylinder engine with quattro all-wheel drive to create a discreet yet formidable performance package that could embarrass far more exotic machinery.

The heart of the UrS4 was the AAN engine — a 2.2-liter inline five-cylinder unit with a single overhead camshaft driving 20 valves (four per cylinder) and a KKK K24 turbocharger. Factory output was 227 horsepower at 5,900 RPM and 350 Nm of torque from 1,950 RPM, figures that were impressive for the early 1990s but only hinted at the engine's true potential. The five-cylinder configuration gave the AAN a distinctive sound — a warbling, off-beat exhaust note that was completely unlike any four, six, or eight-cylinder engine. This sound became an Audi signature and is still revered by enthusiasts.

The AAN engine quickly became legendary in the tuning community for its enormous power potential. The robust iron block, forged crankshaft, and strong bottom end could support significantly more power than the factory 227 horsepower. With relatively simple modifications — a larger turbocharger, upgraded fuel system, and engine management tuning — outputs of 350 to 400 horsepower were readily achievable. Heavily modified examples have exceeded 700 horsepower on the same basic engine block. This tuning potential made the UrS4 a cult hero in the forced-induction community.

The quattro all-wheel-drive system used a Torsen center differential to distribute power between the front and rear axles, providing excellent traction in all conditions. The system was permanently engaged — no driver intervention required — and worked seamlessly with both the 6-speed manual and optional 4-speed automatic transmissions. The 6-speed manual, supplied by Getrag, was strongly preferred by enthusiasts for its positive shift action and the control it provided over the powertrain.

From the outside, the UrS4 was remarkably subtle for a car of its capabilities. It shared its body with the standard Audi 100 (later renamed A6), distinguished only by modest S4 badges, subtly flared wheel arches, unique alloy wheels, and quad exhaust tips. The understated styling was deliberate — Audi's philosophy in the early 1990s was to avoid the aggressive styling of competitors like BMW's M cars. The UrS4 was a sleeper in every sense: a car that could cruise quietly at highway speeds, transport four adults in comfort, and then leave sports cars in its wake when the turbo spooled.

The interior was typically Audi — well-built, ergonomically sound, and trimmed in quality materials. Leather sport seats, a thick-rimmed steering wheel, and complete instrumentation including a boost gauge gave the driver all the necessary information and support. The dashboard layout was clean and logical, with excellent build quality that has proven durable over the decades since production.

The UrS4 was available as both a sedan and an Avant (wagon), with the Avant being rarer and commanding a premium today. Both body styles offered the same mechanical specification. For the 1995 model year, the car was renamed S6, reflecting Audi's shift from the 100 nameplate to A6, though the mechanical specification remained largely unchanged.

Total production was limited by the car's positioning at the top of Audi's sedan range and its niche appeal. Approximately 7,865 UrS4s were produced across all markets and body styles. The car competed against the BMW M5 (E34) and was generally considered to offer superior all-weather capability through its quattro system, though the BMW was sharper to drive on dry roads.

Today, the UrS4 occupies a sweet spot in the collector market. It is affordable enough to purchase and modify but rare enough to hold its value. Clean, unmodified examples with documented service history are increasingly sought after, while well-built, high-horsepower modified examples have their own dedicated following. The UrS4 community is passionate and knowledgeable, supported by specialist suppliers and forums that make ownership and maintenance practical. As the first Audi S-car sedan, it represents the beginning of a performance lineage that continues to this day.