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Mercedes-Benz OM603.970 specs: 3.4L (210 ci) 6-cylinder, 89 x 92.4 mm (3.5039 x 3.6378 in) bore and stroke, 22:1 compression. Built 1990–1991.
The Mercedes-Benz OM603.970 is close to square: 3.5039" bore against 3.6378" stroke, within 3.7%, which splits the difference between a high-revving layout and a torque layout. The 3.6378" stroke puts mean piston speed at 4,000 ft/min around 6,600 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 35.0 ci (574 cc).
At 22:1 this is a compression-ignition engine: the ratio is the heat source that lights the fuel, not a knock limit to be managed.
It is one of 2 engines in the Mercedes-Benz 210ci family, all of them 210 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions across 1990–1991.
| Displacement | 210 ci / 3.4 L |
|---|---|
| Bore | 3.5039" |
| Stroke | 3.6378" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 22:1 |
| Bore/stroke ratio | 0.963 |
| Fuel type | diesel |
|---|---|
| Years | 1990–1991 |
| Bore/stroke character | 0.963 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,638 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 35.0 ci |
| Static compression | 22:1 — high enough that pump premium or better is normally required |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1990 | — | OM603.970 |
| 1991 | — | OM603.970 |
1 factory vehicle, 1990–1991. Each year opens that model's engine table.