In 1984, Audi introduced a four-valve cylinder head for its five-cylinder engine for the first time in the Sport quattro. Derived directly from the company's rally program, this 20-valve technology significantly improved cylinder filling and laid the foundation for a new generation of high-performance production engines. In 1989, Audi brought this technology into regular series production with the 220 hp 3B engine used in the Audi 200 quattro 20V. This development ultimately led to the legendary five-cylinder engines of the Audi S2, S4, and RS2.
For the new engine, Audi retained its proven architecture featuring a robust cast-iron cylinder block, a displacement of 2,226 cm³, and the characteristic dimensions of 81.0 mm bore and 86.4 mm stroke.
The most significant innovation of the 3B engine was its newly developed 20-valve cylinder head. While previous Audi turbocharged five-cylinder engines utilized two valves per cylinder, the 3B employed four valves per combustion chamber for the first time. This allowed considerably larger intake and exhaust flow areas and substantially improved gas exchange efficiency. The result was a higher volumetric efficiency, improved high-rpm performance, and significantly greater potential for future power increases.
In addition to its advanced cylinder-head design, the engine incorporated several cutting-edge technologies. These included a KKK K24 exhaust-gas turbocharger, a high-performance intercooler, and a Bosch Motronic engine management system with knock control. This combination delivered exceptional performance for its era while maintaining the durability and everyday usability expected of a production Audi. Despite its turbocharged configuration, the engine featured a relatively high compression ratio of 9.3:1, contributing to its responsive power delivery.
The 3B also served as the technical foundation for an entire generation of Audi high-performance engines. In 1992, Audi further developed the design into the ABY engine, which introduced individual ignition coils, an upgraded Motronic engine management system, and optimized boost-pressure control. As a result, power output increased to 230 hp, while torque rose to 350 Nm. This engine family subsequently evolved into the AAN engine used in the Audi S4 and ultimately into the legendary ADU engine of the Audi RS2 Avant, producing 315 hp.
In the Audi Coupé S2, the 20-valve five-cylinder engine was designed to operate on 98 RON premium unleaded fuel. However, its cylinder-selective knock-control system, utilizing two knock sensors, also allowed reliable operation on 95 RON unleaded gasoline. In this case, engine management adjusted ignition timing accordingly, resulting in a reduction in power and torque while maintaining safe and reliable operation.