In this section, the aim is to cover the important subjects relating to the fabulous engines in the Audi S2. The links above will eventually open into chapters on the various aspects of the engine and major components such as the turbo, the ECU and the wonders of boost control. Some discussion of tuning options - especially in the area of chip upgrades will be added here in due course.

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The 3B engine fitted to the early S2 models (MY91 & 92 only) is pretty much identical to the 20V turbocharged RR engined which was fitted to the last generation of the UR quattro which ceased production in 1991. Both use the same trusty 2226cc block, a KKK24 turbo and identical Motronic engine management systems. The task of shoe-horning this engine into the series 4 Coupe was contracted to Schmidt Motorsport by Audi in 1990. The only differences to the RR installation (AFAIK) are in the location of some ancillary components. One major difference, not directly related to engine, is that the RR application uses the super-strength '016' transmission whilst the 3B in the S2 Coupe used the same '01A' transmission as was fitted to the normally aspirated 20V Coupe quattro.

The torque characteristic of the 3B engine is factory tuned by the ECU to be just inside the safe operating margins of the 01A gearbox. As such, the 01A transmission is the weakest link in the chain for anyone considering big power & torque hikes on their beloved 3B engined S2. Fortunately the 016 transmission can be bolted onto the 3B engine with no major difficulty. The correct clutch friction plate is required to ensure a match with the input shaft on the 016 tranny. Details to follow in the transmission chapter.
 

After the launch of the S2, Audi developed a direct descendent of the 3B engine for use in the 100 bodied S4 (UrS4 and UrS6). This engine, known as the AAN engine was Audi's first factory engine to feature a direct ignition system. The advantage of this technique is that each cylinder has it's own miniature coil pack mounted  directly above the spark plug which ensures a healthier HT voltage than the previous system which relied on the traditional use of a mechanical distributor and HT leads to steer energy from a single coil pack into one of five cylinders.

More details on the workings of Direct Ignition in its own chapter, but suffice to say the Motronic electronics on the AAN engines (and its ABY & ADU derivatives) are more sophisticated than their 3B and RR predecessors. Some 3B owners will already know of the weakness in some distributor gears which causes an annoying rattle.

The earliest AAN engines retained the use of a distributor body to house the hall effect sensor. The location for this sensor was moved to just behind the camshaft sprocket on later AAN engines so as to obviate the need for any mechanical adjustment on the distributor (which is in a very awkward location). This same distributorless scheme was used on the ABY engine when it was introduced on the S2 Coupe for the 1993 model year in the Autumn of 1992. An identical setup for the ignition system was retained by Audi and Porsche for the RS2 with its ADU engine.