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Honda ES1 / A18A, twin carburetors specs: 1.8L (111.7 ci) 4-cylinder, 80 x 91 mm (3.1496 x 3.5827 in) bore and stroke, 9.4:1 compression. Rated 100 hp.
The Honda ES1 / A18A, twin carburetors is undersquare — the 3.5827" stroke exceeds the 3.1496" bore by 12.1% — a layout that trades peak RPM for leverage and torque low in the range. The 3.5827" stroke puts mean piston speed at 4,000 ft/min around 6,700 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 27.9 ci (458 cc).
9.4:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 4 engines in the A-series family, all of them 111.7 ci — the differences between them are in compression, heads and rating, not displacement. 5 factory variants share these dimensions, rated at 100 hp across 1983–1987.
| Displacement | 111.7 ci / 1.8 L |
|---|---|
| Bore | 3.1496" |
| Stroke | 3.5827" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9.4:1 |
| Bore/stroke ratio | 0.879 |
| Valvetrain | SOHC |
|---|---|
| Fuel type | gas |
| Advertised HP | 100 hp |
| Years | 1983–1987 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1983 | ES1 net | 100 @ 5500 | 109 lb-ft @ 4000 | 9.4:1 |
| 1984 | ES1 net | 100 @ 5500 | 109 lb-ft @ 4000 | 9.4:1 |
| 1985 | ES1 net | 100 @ 5500 | 109 lb-ft @ 4000 | 9.4:1 |
| 1986 | ES1 net | 100 @ 5500 | 109 lb-ft @ 4000 | 9.4:1 |
| 1987 | ES1 net | 100 @ 5500 | 109 lb-ft @ 4000 | 9.4:1 |
Factory specification sheet.
| Bore/stroke character | 0.879 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,583 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 27.9 ci |
| Static compression | 9.4:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| 1983 | 100 hp | ES1 / A18A, twin carburetors |
| 1984 | 100 hp | ES1 / A18A, twin carburetors |
| 1985 | 100 hp | ES1 / A18A, twin carburetors |
| 1986 | 100 hp | ES1 / A18A, twin carburetors |
| 1987 | 100 hp | ES1 / A18A, twin carburetors |
1 factory vehicle, 1983–1987. Each year opens that model's engine table.