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Honda B20A5 specs: 2.0L (119.5 ci) 4-cylinder, 81 x 95 mm (3.1890 x 3.7402 in) bore and stroke. Rated 135 hp, 1988–1991. Used in the Honda Prelude.
The Honda B20A5 is undersquare — the 3.7402" stroke exceeds the 3.189" bore by 14.7% — a layout that trades peak RPM for leverage and torque low in the range. The 3.7402" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 29.9 ci (490 cc).
It is one of 4 engines in the Honda 120ci family, the smallest at 119.5 ci. 4 factory variants share these dimensions, rated at 135 hp across 1988–1991.
| Displacement | 119.5 ci / 2 L |
|---|---|
| Bore | 3.189" |
| Stroke | 3.7402" |
| Cylinders | 4 |
| Configuration | I4 |
| Bore/stroke ratio | 0.853 |
| Fuel type | gas |
|---|---|
| Firing order | 1-3-4-2 |
| Advertised HP | 135 hp |
| Years | 1988–1991 |
| Bore/stroke character | 0.853 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,740 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 29.9 ci |
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 |
|---|---|---|
| 1988 | 135 hp | B20A5 |
| 1989 | 135 hp | B20A5 |
| 1990 | 135 hp | B20A5 |
| 1991 | 135 hp | B20A5 |
1 factory vehicle, 1988–1991. Each year opens that model's engine table.