While having sex with a girl from behind (doggystyle, with both hands on her ass cheeks) you use your right thumb to apply light pressure to her
asshole (the "B" button) therefore initiating turbo mode. The pace of copulation will noticeably increase along with a pleasant turbo moaning sound.
Be careful though, too much and she will overheat with uncomfort and
get bitchy. You will then be sidelined for a while while she tells you to "stop fingering my
asshole". Fucking may resume, however you may have already lost the race.
Use sparingly for that extra
boost of speed, preferably while coming inside of her.
We could tell when
Rod was Excitebiking his girlfriend because the
banging got louder, the
pitch of moans changed, and eventually we would hear him giggling as she yelled at him.