The
BMW S38 is a straight-6 DOHC petrol engine which replaced the
M88 and was produced from 1984-1995. 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
The BMW M5 is a high performance variant of the BMW 5 Series marketed under the BMW M sub-brand. It is considered an iconic vehicle in the sports sedan category. The majority of M5s have been produced in the sedan (saloon) body style, but in so ...
switched to the
S62 V8 engine. There is therefore no direct successor to the S38, however the
BMW S50
The BMW M50 is a straight-6 DOHC petrol engine which was produced from 1990 to 1996. It was released in the E34 520i and 525i, to replace the M20 engine.
In September 1992, the M50 was upgraded to the M50TU ("technical update"), which was BMW' ...
engine took over as BMW's high performance straight-6 engine.
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
A catalytic converter is an vehicle emissions control, exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalysis, catalyzing a redox chemic ...
, dual-row
timing chain
In a piston engine, either a timing belt (also called a ''cambelt'') or timing chain or set of timing gears is used to synchronize the rotation of the crankshaft and the camshaft. This synchronisation ensures that the engine's valves open and cl ...
and a shorter
camshaft duration. As per the M88/3, the S38 uses a
DOHC
An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...
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 and a
stroke of .
Applications:
* 1986-1987
E28 M5 - Canada, Japan and USA
* 1986-1988
E24 M6 - Canada, Japan and USA
* 1987-1989
E24 M635CSi - models with
catalytic converter
A catalytic converter is an vehicle emissions control, exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalysis, catalyzing a redox chemic ...
S38B36
For the S38B36, the displacement was increased to .
This was achieved by increasing the stroke by to ,
[ by using a new forged steel crankshaft.]mass airflow sensor
A mass (air) flow sensor (MAF) is a sensor used to determine the mass flow rate of air entering a fuel-injected internal combustion engine.
The air mass information is necessary for the engine control unit (ECU) to balance and deliver the corre ...
(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 , by increasing the boredom to and the stroke to .[
The engine management was upgraded to Motronic 3.3 and the ignition system was upgraded to ]coil-on-plug ignition
A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plu ...
. Other changes included the compression ratio increasing to 10.5:1, a dual-mass flywheel
A dual-mass flywheel (DMF or DMFW) is a rotating mechanical device that is used to provide continuous energy (rotational energy) in systems where the energy source is not continuous, the same way as a conventional flywheel acts, but damping any ...
s, an exhaust manifold made in Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
, larger intake and exhaust valves, lighter pistons, and the throttle bodies increasing by to .
References
{{DEFAULTSORT:BMW S38
S38
Straight-six engines
Gasoline engines by model