BMW S38

S38B35

The initial version of the S38 has a bore of 93.4 mm (3.7 in) and a stroke of 84 mm (3.3 in).

Applications:

• 1984-1988 E28 M5 - North America only
• 1986-1989 E24 M6 - North America only
• 1987-1989 E24 M635CSi - models with catalytic converter^[5]

S38B36

For the S38B36, the displacement was increased to 3,535 cc (216 cu in).^[5] This was achieved by increasing the stroke by 2 mm (0.1 in) to 86 mm (3.4 in),^[1] by using a longer forged steel crankshaft.^[6] Other changes included revised camshafts, compression ratio increasing to 10:1, a variable-length inlet manifold (to improve low-rev torque),^[1] equal length stainless steel exhaust headers^[7] a hotwire mass airflow sensor (MAF) and Bosch Motronic engine management.

Applications:

• 1989–1992 E34 M5 (worldwide)
• 1992–1996 E34 M5 - North America only

S38B38

In 1992, BMW further enlarged the S38 engine to 3795 cc, by increasing the stroke to 90 mm (3.5 in). Power increased to 250 kW (340 hp) and torque increased to 400 N⋅m (300 lb⋅ft).^[5]

The engine management was upgraded to Motronic 3.3 and the ignition system was upgraded to coil-on-plug ignition. Other changes include the compression ratio increasing to 10.5:1, a dual-mass flywheel, an exhaust manifold made from Inconel, larger intake and exhaust valves, lighter pistons, and the throttle bodies increasing by 4 mm to 50 mm (2.0 in).^[6]

Applications:

• 1992-1996 E34 M5 - European-specification