They fire instantaneously. Even before fully warming up xenons will be brighter than halogens.
And all E92/E93 and E90 LCI xenon work this way.
AW/Terra | ZSP | ZPP | ZCW | iDrive | CA
Mods: BC BR | OEM Blacklines | M-tech rear | custom dual exhaust | M3 steering wheel | BMW SSK | ZHP shift knob | BMW Performance rep spoiler
Varrstoen ES1 19x9.5+20 Front, 19x11+25 rear