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Lexus 1UR-FSE specs: 4.6L (280.7 ci) 8-cylinder, 94 x 82.7 mm (3.7008 x 3.2559 in) bore and stroke, 11.8:1 compression. Rated 380 hp. DOHC.
The Lexus 1UR-FSE is oversquare — the 3.7008" bore exceeds the 3.2559" stroke by 13.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.2559" 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 (575 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, the smallest at 280.7 ci. Factory fitments include the Lexus LS 460, Lexus GS 460.
| Displacement | 280.7 ci / 4.6 L |
|---|---|
| Bore | 3.7008" |
| Stroke | 3.2559" |
| Cylinders | 8 |
| Compression ratio | 11.8:1 |
| Bore/stroke ratio | 1.137 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 380 hp |
| Bore/stroke character | 1.137 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,256 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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