Turbo Start (TS) means that turbo you can get at the start of the race by doing the normal Mario Kart "Rocket Start".

In this game you are not restricted to the start, instead you can do it everytime you are in neutral gear. (Manual transmission have an advantage in this sense)

Turbo Start = Neutral Gear + A + [Timing] R+A (Gear Up)

What timing? Well, on the rpm (The right-down corner) you need to get the bar to the orange part, and the change the gear up.

The fact that you only need to be on Neutral Gear to do the TS allow to do multiple turbos before the GO. You only need to change the gears down to neutral and do the TS again. AND yes, you can do a TS mid race, if you crash or lose Multidrift, just go to neutral and TS.

Why is it important to be able to do multilple TS before the GO? So you can be more consistant with them and be able to TS all the way thought a Full Cruis'n The World or Championship Run, and you dont need to restart the race or go start slow.

Additionally, you can cancel the wheelie animation, or any grounded "trick" animation (wheelie, side ways car, drifting) by releasing the acceletator.

Time: 0:40, I cancel the turbo wheelie animation.