The phrase "open throttle" means to push down on the gas pedal fully or completely, which allows the engine to produce the maximum amount of power and speed.
My motto is wide open throttle at all times, I enjoy life to the fullest every minute. (sugarmommaclub.com)
The veteran driver works the low gears with ease and energy, whipping us through corners and cracking open the throttle of the twin - turbo 430 - hp inline six - cylinder. (automobilemag.com)
You would waste more energy having to use a wide open throttle for cruising - instead many cars have an overdrive. (mechanics.stackexchange.com)