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
No; you would never do this as an everyday driver; you’d ruin your car
Racing vehicles use this to “launch” or start the race at high rpm’s.
Holding the breaks keep the car in place; revving the engine at high rpm’s allow for a faster than start than if they had been at idle rpm’s
Power braking is a method for launching a car with an automatic transmission by holding the brakes and increasing engine rpm. It has basically nothing to do with braking a car in motion. It is probably most commonly used to initiate a burnout in RWD automatic cars.
It’s not great for your car as it builds heat in the torque converter of the transmission. It can also be hard on your brakes.
Race cars with automatic transmissions are unlikely to use power braking, since they rarely use torque-converter automatics. Some of them may also have launch control features.
Someone trained to drive a car with evasive techniques (i.e., a Secret Service driver) might use this, but I can’t think of much else outside of a race track.
I assume by “power braking” you mean applying gas and brakes simultaneously.
The only time this is useful, as far as I know, is rally driving in a FWD car. Sometimes you *want* oversteer when racing, and it’s hard to get a FWD car to do that. It can be done, however, by applying gas and brake at the same time – they cancel each other out at the front wheels, leaving brake-only at the rear wheels, and under the right conditions this will make the rear end step out in a nicely controllable way.
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.
In the off-chance you’re referring to left-foot braking while also modulating the throttle during cornering maneuvers…
Doing this is a very advanced method of trying to balance the weight transfer of the car front to back while also separately modifying the grip of the drive and non-drive wheels via the brakes.
There’s really no scenario where a lay-person should try this because it’s likely just going to make a situation worse. Just let the electronics (ABS, TC, DSC, etc) do the hard work.
If you’re an advanced driver (many hundreds or thousands of hours on road courses), you can use this to improve your lap times on track.
Of course, race tracks don’t change much so you have time to learn a choreographed sequence of actions for each corner. Emergency/evasive maneuvers aren’t like that. You could, in theory, get good enough that your reaction times and skills might help you, but you’re better off just driving like you’re on the street and not attempting race track activities.
On turbo cars I’ve heard this referred to as “brake boosting” the idea is that the turbos need exhaust gas to spool up and create boost and depending on the size of the turbo boost can come on at different rpm levels. If you don’t start creating boost until 3500 rpm you would apply gas and brakes until you were at 3500 rpm or greater that way when you let go of the brakes to go your car is already in its boost threshold making better power. Are there scenarios where a layman would use it? Sure want to be a jackass and launch as fast as you can from a red light? practically there’s no good reason to do it and it’s definitely not good for your vehicle but boy can it be fun. I don’t really think there is a good reason to do it in most naturally aspirated cars except maybe stop light on a real steep hill and you don’t want to roll back slowly let off the brake while you’re accelerating but I think that’s a whole different thing than what you’re asking.
You’ll occasionally see pro drivers apply brake and throttle simultaneously, usually as an advanced technique to help control car balance through tricky sections of track. It’s not used often, but a skilled driver can use it to help maintain higher mid-corner speeds, set up a tricky corner entry or stabilize the car to get on the gas sooner.
Basically, lightly dabbing the brake while under throttle shifts the car’s balance forward, which can give you more front-end grip. You might do this in a corner that can’t normally quite be taken at full throttle, but perhaps could be if you find a touch of extra rotation on corner entry. Dab the brake while flat and you might get that corner entry correct. (Most people would simply lift the throttle to get that same weight transfer and rotation, but it’s possible a light dab of brake is marginally faster.)
Applying (slight) throttle through a braking zone corner does the opposite and can help in stabilizing the front-back weight transfer through a corner. You might do this through a long sweeping turn that has you on the brake through a long tricky braking section, with all the car’s weight over the front axle. Add a dash of maintenance throttle and you might shift the weight slightly to the rear, giving you more confidence you won’t experience oversteer.
You might also use very light throttle to help control a car that’s set up with aggressive engine braking. Maybe the track has a very heavy braking zone that benefits from that extra engine braking, but the same effect destabilizes the car in a different part of the track. One solution might be to apply some light maintenance throttle to lessen the downside effect of engine braking.
All that said, this technique is rare even at the highest level, and you’ll never need to do this as a layperson.
An example is here, comparing Hamilton’s lap against Verstappen at Silverstone. Note how Hamilton is on the throttle at about 20% through several braking zones, and how this helps him maintain a speed advantage over Verstappen.
[https://www.reddit.com/r/formula1/comments/i28t52/oc_qualifying_telemetry_hamiltonverstappen_more/#lightbox](https://www.reddit.com/r/formula1/comments/i28t52/oc_qualifying_telemetry_hamiltonverstappen_more/#lightbox)
When you are down shifting hard or braking in a turn you can throw the balance of the car and lose grip on the rear end. By doing heel and toe you can revolution match the engine with the down shift and maintain balance.
Heel-and-toe (and left foot braking falls into this category) braking shows up a lot in Rally. When staying on power in the turn, or intentionally getting the car loose is needed.
look for the “Scandinavian flick”. It is the classic for demonstration of a car staying on power as the car is “flicked” around a U-turn.
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