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Acura G25A4 specs: 2.5L (150 ci) 5-cylinder, 85 x 86.4 mm (3.3465 x 3.4016 in) bore and stroke, 9.6:1 compression. Rated 176 hp, 1996–1998.
The Acura G25A4 is close to square: 3.3465" bore against 3.4016" stroke, within 1.6%, which splits the difference between a high-revving layout and a torque layout. The 3.4016" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 5 cylinders displaces 30.0 ci (492 cc).
9.6:1 is in the range that usually runs on pump premium.
3 factory variants share these dimensions, rated at 176 hp across 1996–1998.
| Displacement | 150 ci / 2.5 L |
|---|---|
| Bore | 3.3465" |
| Stroke | 3.4016" |
| Cylinders | 5 |
| Compression ratio | 9.6:1 |
| Bore/stroke ratio | 0.984 |
| Fuel type | gas |
|---|---|
| Redline | 6,800 rpm (factory limit) |
| Advertised HP | 176 hp |
| Years | 1996–1998 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1996 | G25A4 net | 176 @ 6300 | 170 lb-ft @ 3900 | — |
| 1997 | G25A4 net | 176 @ 6300 | 170 lb-ft @ 3900 | — |
| 1998 | G25A4 net | 176 @ 6300 | 170 lb-ft @ 3900 | — |
Factory specification sheet.
| Bore/stroke character | 0.984 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,402 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.0 ci |
| Static compression | 9.6:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| 1996 | 176 hp | G25A4 |
| 1997 | 176 hp | G25A4 |
| 1998 | 176 hp | G25A4 |
1 factory vehicle, 1996–1998. Each year opens that model's engine table.