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Volkswagen FG specs: 1.5L (90 ci) 4-cylinder, 76.5 x 80 mm (3.0118 x 3.1496 in) bore and stroke, 8.2:1 compression. Built 1975.
The Volkswagen 90ci (FG) is close to square: 3.0118" bore against 3.1496" stroke, within 4.4%, which splits the difference between a high-revving layout and a torque layout. The 3.1496" stroke does not reach 4,000 ft/min of mean piston speed until about 7,600 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 22.5 ci (369 cc).
8.2:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Volkswagen 90ci family, all of them 90 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 90 ci / 1.5 L |
|---|---|
| Bore | 3.0118" |
| Stroke | 3.1496" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 8.2:1 |
| Bore/stroke ratio | 0.956 |
| Fuel type | gas |
|---|---|
| Years | 1975 |
| Bore/stroke character | 0.956 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,150 ft/min — conservative for a street engine |
| Displacement per cylinder | 22.5 ci |
| Static compression | 8.2:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.
1 factory vehicle, 1975. Each year opens that model's engine table.