BMW S38
Template:Infobox automobile engine The BMW S38 is a straight-6 DOHC petrol engine which replaced the M88 and was produced from 1984–1995.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> 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. There is therefore no direct successor to the S38, however the BMW S50 engine took over as BMW's high performance straight-6 engine.
Design
The S38 is based on the M88/3 engine.<ref name="usautoparts">Template:Cite web</ref> 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.<ref>Template:Cite web</ref> As per the M88/3, the S38 uses a DOHC valvetrain with shim-and-bucket valve actuation.<ref>Template:Cite web</ref> Air intake is via six individual throttle bodies with intake trumpets, fed by a cast aluminum intake plenum.<ref>Template:Cite web</ref> Template:Clear right
Versions
| Version | Displacement | Power | Torque | Years |
|---|---|---|---|---|
| S38B35 | Template:Convert | Template:Convert at 6,500 rpm |
Template:Convert at 4,500 rpm |
1986–1989 |
| S38B36 | Template:Convert | Template:Convert at 6,900 rpm |
Template:Convert at 4,750 rpm |
1989–1993 |
| S38B38 | Template:Convert | Template:Convert at 6,900 rpm |
Template:Convert at 4,750 rpm |
1991–1995 |
S38B35
The initial version of the S38 has a bore of Template:Convert and a stroke of Template:Convert.
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<ref name="bmwheaven">Template:Cite web</ref>
S38B36
For the S38B36, the displacement was increased to Template:Convert.<ref name=bmwheaven /> This was achieved by increasing the stroke by Template:Convert to Template:Convert,<ref name=usautoparts/> by using a new forged steel crankshaft.<ref name="www.bmwmregistry.com E34 M5">Template:Cite web</ref> Other changes included revised camshafts, compression ratio increasing to 10:1, a variable-length inlet manifold (to improve low-rev torque),<ref name=usautoparts /> equal length stainless steel exhaust headers<ref>Template:Cite web</ref> a hotwire mass airflow sensor (MAF) and Bosch Motronic engine management.
Applications:
S38B38
In late 1991, BMW further enlarged the S38 engine to Template:Convert, by increasing the bore to Template:Convert and the stroke to Template:Convert.<ref>Template:Cite web</ref> Power increased to Template:Convert at 6,900 rpm and torque increased to Template:Convert at 4,750 rpm.<ref name=bmwheaven/>
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 Template:Convert to Template:Convert.<ref name= "www.bmwmregistry.com E34 M5"/>
Applications: