BMW S38

Design

The S38 is based on the M88/3 engine. Compared to the M88/3, the S38 has a lower compression ratio (9.8:1), simplified exhaust manifold, catalytic converter, dual-row timing chain and a shorter camshaft duration. As per the M88/3, the S38 uses a DOHC valvetrain with shim-and-bucket valve actuation. Air intake is via six individual throttle bodies with intake trumpets, fed by a cast aluminum intake plenum.

Versions

S38B35

The initial version of the S38 has a bore of 93.4 mm and a stroke of 84 mm.

Applications:

• 1986–1987 E28 M5 - Canada, Japan and US
• 1986–1988 E24 M6 - Canada, Japan and US
• 1987–1989 E24 M635CSi - models with catalytic converter

S38B36

For the S38B36, the displacement was increased to 3535 cc. Other changes included revised camshafts, compression ratio increasing to 10:1, a variable-length inlet manifold (to improve low-rev torque), a hotwire mass airflow sensor (MAF) and Bosch Motronic engine management.

Applications:

• 1988–1992 E34 M5 (worldwide)
• 1989–1993 E34 M5 - Canada and US

S38B38

In late 1991, BMW further enlarged the S38 engine to 3795 cc, by increasing the bore to 94.6 mm and the stroke to 90 mm.{{cite web

The engine management was upgraded to Motronic 3.3 and the ignition system was upgraded to coil-on-plug ignition. Other changes included the compression ratio increasing to 10.5:1, a dual-mass flywheel, an exhaust manifold made of Inconel, larger intake and exhaust valves, lighter pistons, and the throttle bodies increasing by 4 mm to 50 mm.

Applications:

• 1991–1995 E34 M5 - European-specification

References

References

1. "BMW S38B35 car engine".
2. "BMW S38B38 automotive engine".
3. "BMW S38 engine".
4. "FAQ E28 M5".
5. "BMW S38 Valve adjustment tool".
6. "BMW M88 and S38 M-Tech 24 Valve Six Cylinder Engines".
7. "Information on Motorsport engines".
8. "FAQ E34 M5".
9. "Exhaust manifold - M5 3.6 E34 Sedan USA S38".