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Volkswagen JH / HT specs: 1.8L (109 ci) 4-cylinder, 81 x 86.4 mm (3.1890 x 3.4016 in) bore and stroke. Built 1984–1988. Used in the Volkswagen Scirocco.
The Volkswagen JH / HT is undersquare — the 3.4016" stroke exceeds the 3.189" bore by 6.3% — a layout that trades peak RPM for leverage and torque low in the range. 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 4 cylinders displaces 27.3 ci (447 cc).
It is one of 7 engines in the Volkswagen 109ci family, all of them 109 ci — the differences between them are in compression, heads and rating, not displacement. 5 factory variants share these dimensions across 1984–1988.
| Displacement | 109 ci / 1.8 L |
|---|---|
| Bore | 3.189" |
| Stroke | 3.4016" |
| Cylinders | 4 |
| Configuration | I4 |
| Bore/stroke ratio | 0.938 |
| Fuel type | gas |
|---|---|
| Years | 1984–1988 |
| Bore/stroke character | 0.938 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,402 ft/min — conservative for a street engine |
| Displacement per cylinder | 27.3 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 |
|---|---|---|
| 1984 | — | JH / HT |
| 1985 | — | JH / HT |
| 1986 | — | JH / HT |
| 1987 | — | JH / HT |
| 1988 | — | JH / HT |
1 factory vehicle, 1984–1988. Each year opens that model's engine table.