Features   |   Identification   |   Component Locations   |   How it Works There were three major revisions of the 2.8l 12v engine: The AAH V6 was the first 12v engine. The AFC version had several modifications to the running gear and lubrication system. See the Features section for more details. The ACK version added OBD-II support. Audi started producing the AFC engine around December of 1994. However, there was a run of engines that had some of the new AFC features, but not all of them -- they were produced between August 1994 and May 1995. Here are some hints to help you figure out which engine you have: The engine code letters and serial number are stamped on the left side of the engine block, between the cylinder head and the power steering pump. In addition, an adhesive label on the timing belt cover lists the engine code and serial number. AFC engines are identified by a punch mark or a recess in the lifting eye on the front of the right cylinder head. Some engines have the mark on the lifting eye, but are stamped as AAH engines. These engines, which were produced between August 1994 and May 1995, are referred to as AAH/AFC on this site.       Disclaimer