Bore, stroke, displacement and compression for all 2 Hyundai U engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 91.5–97.6 ci |
|---|---|
| Cylinders | 4 |
| Bore | 2.953–3.039" |
| Stroke | 3.327" |
| Compression | 17.3–17.8:1 |
| Advertised power | 110–128 hp |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| D4FB | 97.6 ci | 3.0394" × 3.3268" | 17.3:1 | 128 |
| D4FA | 91.5 ci | 2.9528" × 3.3268" | 17.8:1 | 110 |
Stroke is constant at 3.3268" across the family — the displacement spread comes from bore, so these share a crank and differ in the block.
All are undersquare — stroke larger than bore, favouring torque low in the range.
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.