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Mazda 20 LF specs: 1.999L (122 ci) 4-cylinder, 87.5 x 83.1 mm (3.4449 x 3.2717 in) bore and stroke, 10.8:1 compression. Rated 158 hp. DOHC.
The Mazda 20 LF is oversquare — the 3.4449" bore exceeds the 3.2717" stroke by 5.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.2717" stroke does not reach 4,000 ft/min of mean piston speed until about 7,350 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 30.5 ci (500 cc).
10.8:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 9 engines in the MZR family, the smallest at 122 ci. Factory fitments include the MX-5 Miata NC, Mazda3, Mazda5 and 3 others.
| Displacement | 122 ci / 1.999 L |
|---|---|
| Bore | 3.4449" |
| Stroke | 3.2717" |
| Cylinders | 4 |
| Compression ratio | 10.8:1 |
| Bore/stroke ratio | 1.053 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 158 hp |
| Bore/stroke character | 1.053 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,272 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 10.8:1 — in the range that usually runs on pump premium |
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