The first Audi five-cylinder engine, identified by the engine code WC, was introduced in 1976 in the new Audi 100 C2 (Type 43) and marked a milestone in German automotive engineering. Initially offered as the 2.1-litre fuel-injected 5E, the engine produced 136 hp (100 kW) at 5,700 rpm and 185 Nm of torque at 4,200 rpm. It displaced 2,144 cm³, with a 79.5 mm bore and an 86.4 mm stroke. The compression ratio was 9.3:1.
The new engine was derived from Audi's proven EA827 four-cylinder engine. The cylinder block was manufactured from high-strength cast iron and was essentially an extended version of the existing four-cylinder design. The crankshaft was supported by six main bearings, providing exceptional rigidity and durability. Its five crankpins were arranged at 72-degree intervals. Since a four-stroke engine requires 720 degrees of crankshaft rotation to complete a full operating cycle, the five-cylinder configuration resulted in evenly spaced firing intervals of 144 degrees. Combined with the firing order 1-2-4-5-3, this created the distinctive Audi five-cylinder sound that remains characteristic to this day.
From a vibration-engineering perspective, an inline five-cylinder possesses unique dynamic characteristics. It runs considerably smoother than an inline four-cylinder, although it does not achieve the perfect primary and secondary balance of an inline six-cylinder. Audi therefore invested significant engineering effort in controlling the free mass moments inherent in the design. The crankshaft was equipped with specially designed counterweights, while a carefully tuned torsional vibration damper and a specifically balanced flywheel were incorporated into the drivetrain. Together, these measures substantially reduced vibration levels and provided a degree of refinement that was remarkable for the period.
The lightweight aluminum cylinder head featured a single overhead camshaft (SOHC) and two valves per cylinder. The camshaft was driven by a toothed timing belt. For the five-cylinder application, Audi developed an extended cylinder head with larger valves than those used in the original four-cylinder engine. The intake valves measured 38 mm in diameter, while the exhaust valves measured 33 mm. The increased valve area improved gas exchange efficiency and contributed to a higher specific power output compared with contemporary four-cylinder engines.
Particularly advanced for its time was the Bosch K-Jetronic fuel injection system, a continuous mechanical fuel injection system. Incoming air was measured by an airflow sensor plate, whose movement was mechanically transmitted to a fuel distributor that metered fuel individually to each cylinder. Compared with conventional carbureted engines, K-Jetronic provided significantly more precise throttle response, improved mixture preparation, and lower fuel consumption and exhaust emissions. Under full-load conditions, the system also incorporated an enrichment function to maximize power output while protecting critical engine components.
The ignition system was equally sophisticated by 1970s standards. Audi employed a transistorized coil ignition system, which provided higher spark energy and more precise ignition timing control than conventional contact-point ignition systems. The distributor was driven directly from the camshaft. This arrangement improved operational reliability and supported the relatively high engine speeds that were unusual for a large executive-class sedan of the era.