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Lexus 2AR-FSE specs: 2.5L (152 ci) 4-cylinder, 90 x 98 mm (3.5433 x 3.8583 in) bore and stroke, 12.5:1 compression. Rated 204 hp. Rod ratio and piston speed.
The Lexus 2AR-FSE is undersquare — the 3.8583" stroke exceeds the 3.5433" bore by 8.2% — a layout that trades peak RPM for leverage and torque low in the range. The 3.8583" stroke puts mean piston speed at 4,000 ft/min around 6,200 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.0 ci (623 cc).
12.5:1 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 5 engines in the AR family, sitting between the 122 ci and 165 ci members. Factory fitments include the Lexus IS 300, Lexus GS 300, Lexus IS 300h and 6 others.
| Displacement | 152 ci / 2.5 L |
|---|---|
| Bore | 3.5433" |
| Stroke | 3.8583" |
| Cylinders | 4 |
| Compression ratio | 12.5:1 |
| Bore/stroke ratio | 0.918 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 204 hp |
| Bore/stroke character | 0.918 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,858 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.0 ci |
| Static compression | 12.5:1 — high enough that pump premium or better is normally required |
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