To earn the Bat Out of Hell achievement/trophy in Gotham Knights, you must “Complete every Batcycle time trial”.
To unlock Batcycle Time Trials you must advance the main questline to Case 04, at which point one Batcycle Time Trial will appear on your map. Head to the start location (marked by a glowing green cube) and summon the Batcycle, then drive through a checkpoint ring to start the race. The Batcycle is slow, clunky and surprisingly ponderous - not a great racing machine. Once the race has begun a timer will pop up, and you must finish the race before the timer expires. Your course will be marked by checkpoint rings, and while driving through them is optional, each checkpoint ring you hit will add 2 seconds to the timer, so while missing one isn’t a problem, missing too many will eventually cause you to run out of time. In addition you can usually find several clock pickups on each course, each of which will add 5 seconds to your timer.
The key to succeeding at these time trials is, ironically, to take it slow. Mistakes and open world randomness will cost you more time than playing it safe will, and while each checkpoint ring doesn’t add a lot of time, there’s a bunch of them in each race and they’re spaced fairly close together. Be methodical and drive cautiously while keeping just enough speed to make your checkpoints and you should do fine. After each race, return to the Belfry and start a new patrol to spawn the next Batcycle Time Trial.