The term used to refer to Volkwagen/Audi's 1.8 litre turbocharged gasoline engine. Features of the engine include:
-a cast iron cylinder block
-aluminum valve cover, oil pan, and crossflow intake
-dual overhead camshafts or DOHC (later revisions included a variable valve timing feature for performance/emissions control)
-5 valves per cylinder, three inlet and two exhaust
-individual ignition coils for each cylinder (no distributor)
-Sequential fuel injection
-drive-by-wire throttle control system
The engine came in several revisions:
transverse: AWD, AWW, AWP, APH/AVC , AWV, ATC, AGU, ARZ, AVJ, AUM, ARX, AWC, BJX, AJH, AQX, AYP, BVP, AJQ, APP, AUQ/ARY, BBU, BVR, APY, AMK, APX, BAM, BFV(240hp)
longitudinal: AMU, BEA, AEB, APU, AWT, BFB, AJL, BEX,
The fact that the engine was originally designed with the use of a turbocharger makes it very compliant to the introduction of higher flow aftermarket turbochargers and high boost with increased fueling. Simple software tuning can increase the engine output to 200+bhp and 250+lb.-ft. of torque. Changes to engine hardware can have the 1.8T engine producing over 300hp.
The cast iron cylinder block along with native forced induction and high compression ratio (9.5:1 stock) allow the 1.8T to produce high output from limited combustion volume.