The naturally aspirated straight-six actually displaces not 2.3 litres but 2.5, enough for 204bhp. The 23i makes up in smoothness and economy what it lacks in punch, and it feels amply quick from the driving seat. Sixty rocks up in 6.6sec and the top speed is only 4mph short of requiring an electronic limiter. The bigger engines go fast for less effort but you can rag the 23i harder because you need to which gets you more involved in the drive.