BMW S38
| BMW S38 engine | |
|---|---|
 S38B36 in an E34 M5 | |
| Overview | |
| Manufacturer | BMW |
| Production | 1986–1995 |
| Layout | |
| Configuration | DOHC straight-6 |
| Chronology | |
| Predecessor | BMW M88 |
The BMW S38 is a straight-6 DOHC petrol engine which replaced the M88 and was produced from 1986-1995. The S38 was originally produced for North America as an equivalent to the M88 with slightly lower power output. In 1989, power output of the S38 was increased and it became the worldwide replacement for the M88.
In 1998, the BMW M5 switched to the S62 V8 engine. Therefore, there is no direct successor to the S38 (however BMW's tradition of high performance straight-6 engines continued with the S50 engine).
Design
The S38 is based on the M88/3 engine.[1] Compared to the M88/3, the S38 has a lower compression ratio (9.8:1), simplified exhaust manifold, catalytic convertor, dual-row timing chain and a shorter camshaft duration.[2] As per the M88/3, the S38 uses a DOHC valvetrain with shim-and-bucket valve actuation.[3] Air intake is via six individual throttle bodies with intake trumpets, fed by a cast aluminum intake plenum.[4]
Models
| Engine | Displacement | Power | Torque | Years |
|---|---|---|---|---|
| S38B35 | 3,453 cc (210.7 cu in) | 190 kW (255 bhp) @ 6500 rpm |
330 N⋅m (243 lb⋅ft) @ 4500 rpm |
1986–1988 |
| S38B36 | 3,535 cc (215.7 cu in) | 232 kW (311 bhp) @ 6900 rpm |
360 N⋅m (266 lb⋅ft) @ 4750 rpm |
1989–1993 |
| S38B38 | 3,795 cc (231.6 cu in) | 250 kW (335 bhp) @ 6900 rpm |
400 N⋅m (295 lb⋅ft) @ 4750 rpm |
1992–1996 |
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:
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:
References
- ^ a b c "BMW S38 engine". www.usautoparts.net. Archived from the original on 18 November 2012.
- ^ "FAQ E28 M5". www.bmwmregistry.com. Retrieved 16 September 2017.
- ^ "BMW S38 Valve adjustment tool". www.bigcoupe.com. Retrieved 16 September 2017.
- ^ "BMW M88 and S38 M-Tech 24 Valve Six Cylinder Engines". www.unixnerd.demon.co.uk. Retrieved 14 September 2017.
- ^ a b c "Information on Motorsport engines". www.bmwheaven.com. Retrieved 14 September 2017.
- ^ a b "FAQ E34 M5". www.bmwmregistry.com. Retrieved 16 September 2017.
- ^ "Exhaust manifold - M5 3.6 E34 Sedan USA S38". www.bmwfans.info. Retrieved 14 September 2017.