So, erection and ejaculation are controlled by autonomic nerves. Therefore, guys you really don’t have too much control over it. It’s all up to the nerves.
In order to remember which splanchnic nerves do erection and which do ejaculation, just think ‘Point and Shoot’.
Point = erection = Pelvic splanchnic nerves
Shoot = ejaculation = Sacral splanchnic nerves