Is there a scenario where a layman would use it (i.e. evasive maneuvers)? In what scenario would a racer use it?
Edit: Yes, I mean accel+brake. Heel-toe, etc
In: Engineering
If you mean braking really hard, and possibly revving slightly as you apply braking force (rather than holding the brakes before launching the car, which is kind of the similar principle) – the reason you might want to do that is to make sure you don’t have a delay between releasing the brake and having full(-ish) power. In a sharp turn where you brake all the way into the turn and to the apex (or whatever turning point you’ve chosen, rather than coasting to a point where you apply power again.. which you’d normally do, because most of us don’t drive f1 or something like that.. Lots of automatic cars that might tempt you to break and throttle, though.. with windups and automatic clutches and things that last a long time. But they usually have a system forcing you to not try).
At that point, on a late, fast turn like that, you might brake as you rev (heel&toe and blabla), so you can release the clutch and have compression enough and throttle on demand. Or you might have prepared to brake down to a fairly high rev as you engage the clutch early, and then brake more because you can’t brake hard enough just by engaging the clutch.
In normal driving, and even very fast race-car driving, there’s usually no reason to do this, though. And it’s kind of a rescue/bad move, imo, or something for a very special situation where you’re hunting for some really small margin.
In a moving start, though, any kind of race-car with slicks and a bit of power is likely going to have a driver who will apply throttle and brake right before the start-signal, and then let go of the brake at the signal. Again, just to get the engine to compression and torque as early as possible.
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