Mercedes-Benz 181ci specs: 88.5 x 80.2 mm (3.4843 x 3.1594 in) bore and stroke, shared by all 3 versions. Displacement, compression and factory ratings.
| Displacement | 181 ci |
|---|---|
| Cylinders | 6 |
| Bore | 3.484" |
| Stroke | 3.158–3.159" |
| Compression | 9.2–10.0:1 |
| Years | 1986–1993 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| M103 | 181 ci | 3.4843" × 3.1594" | 9.2:1 | — |
| M104.980 | 181 ci | 3.4843" × 3.1575" | 10:1 | — |
| M104.981 | 181 ci | 3.4843" × 3.1575" | 10:1 | — |
Every engine here shares a 3.4843" bore; displacement varies by stroke alone, which is the signature of a family built on one block with different cranks.
All are oversquare — bore larger than stroke, which favours revs over low-end torque.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.