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Mercedes-Benz M115 specs: 2.3L (141 ci) 4-cylinder, 93.7 x 83.6 mm (3.6909 x 3.2913 in) bore and stroke, 9:1 compression. Built 1978.
The Mercedes-Benz M115 is oversquare — the 3.6909" bore exceeds the 3.2913" stroke by 12.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.2913" stroke does not reach 4,000 ft/min of mean piston speed until about 7,300 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 35.3 ci (578 cc).
9:1 is low by modern standards and generally happy on regular pump fuel.
| Displacement | 141 ci / 2.3 L |
|---|---|
| Bore | 3.6909" |
| Stroke | 3.2913" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.121 |
| Fuel type | gas |
|---|---|
| Years | 1978 |
| Bore/stroke character | 1.121 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,291 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.3 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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1 factory vehicle, 1978. Each year opens that model's engine table.