its like the 740 / 540 bmws - the early ones were 4.0's but later ones where 4.4's..

850 V12 uprated model was a 5.6

Some 318's are 1.9 litre as well iirc...

BMW have odd names LOL

Not like Ferrari! 308 - 3 litres 8 cylinders, 288 - 2.8 litre 8 cylinders LOL