User blog comment:Silva-zoldyck/what if... they caught annie before transforming?/@comment-7418318-20130924083233/@comment-68.80.160.104-20130926003307

(silva) reiner said eren titan form is more reiliable in chapter either 46 -47-48 one of these chapters.

(Nick) the reason eren did'nt transform in the tunnel when they were testing eren titan power is because at the time they did'nt know eren have to have a set goal before transforms, they just told him to just transform without giving him a goal or a reason to transform.