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Lexus 1UR-FSE specs: 4.6L (281 ci) 8-cylinder, 94 x 83 mm (3.7008 x 3.2677 in) bore and stroke, 11.8:1 compression. Rated 380 hp. Rod ratio and piston speed.
The Lexus 1UR-FSE is oversquare — the 3.7008" bore exceeds the 3.2677" stroke by 13.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.2677" 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 8 cylinders displaces 35.1 ci (576 cc).
11.8:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 10 engines in the UR family, sitting between the 280.7 ci and 346 ci members. Factory fitments include the LS 460, GS 460.
| Displacement | 281 ci / 4.6 L |
|---|---|
| Bore | 3.7008" |
| Stroke | 3.2677" |
| Cylinders | 8 |
| Compression ratio | 11.8:1 |
| Bore/stroke ratio | 1.133 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 380 hp |
| Bore/stroke character | 1.133 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,268 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.1 ci |
| Static compression | 11.8:1 — high enough that pump premium or better is normally required |
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