BMW Z4 E89 (2009 - 2016) - timing belt or chain?

Petrol engines

Model Power \| Displacement \| Cylinder \| Engine	Camshaft drive system Timing belt or chain
BMW Z4 sDrive18i 115 kW / 154 hp / 156 PS \| 1997 cc \| 4 \| N20B20	timing chain
BMW Z4 sDrive20i 135 kW / 181 hp / 184 PS \| 1997 cc \| 4 \| N20B20	timing chain
BMW Z4 sDrive23i 150 kW / 201 hp / 204 PS \| 2497 cc \| 6 \| N52B25	timing chain
BMW Z4 sDrive28i 180 kW / 241 hp / 245 PS \| 1997 cc \| 4 \| N20B20	timing chain
BMW Z4 sDrive30i 190 kW / 255 hp / 258 PS \| 1996 cc \| 6 \| N52B30	timing chain
BMW Z4 sDrive35i 225 kW / 302 hp / 306 PS \| 2979 cc \| 6 \| N54B30	timing chain
BMW Z4 sDrive35is 250 kW / 335 hp / 340 PS \| 2979 cc \| 6 \| N54B30	timing chain