Before we begin covering how to identify which one a corner is, let's first just define what these terms mean:
Exit Speed Corner: If we call a corner an "exit speed corner" we are stating that getting a good exit is our priority in this corner. There is more time to be gained by having an earlier full-throttle application point than a relative increase in entry speed into the corner which would delay our full-throttle point.
Entry Speed Corner: This is simply the opposite of an exit speed corner. In an "entry speed corner" we are identifying our priority as increased entry speed. We are better off rolling in more speed at corner entry which forces us to delay our initial throttle application point and full throttle application point.
The differences between these types of corners are nuanced. Generally, in an exit speed corner, my initial throttle application point comes just before the apex (half car length or so) and the full throttle application point comes before arriving at the exit curb. While in an entry speed corner, my initial throttle will come after the apex (about 1 car length) and the full throttle application spot will come maybe 1 - 2 car lengths after a good exit speed corner full throttle application spot.
Now that we have defined these terms how do we tell if a corner is an exit speed or entry speed corner?
To do this we get a track map or pull up an onboard corner and in each corner we ask ourselves which covers a long distance:
- The braking zone into the corner
- The acceleration zone out of the corner
If 1 is true, then we have an entry speed corner. If 2 is true, we have an exit speed corner.
Why is this important? Well, in every corner we need a very clear goal of what we are trying to achieve and where to place our minimum speed in a corner.
Let's use the following images from my book Sent It: The Art & Science of Racing Cars to try and visualize this a little bit more. If you're familiar with Road Atlanta great, the graph on the left represents turn 6, and the graph on the right represents turn 7. (If you are viewing this on your phone then turn 6 is on top and turn 7 is on the bottom)
The top line shows GPS speed and the bottom line is the time delta between both laps.
Notice that on both laps the red line rolls at more entry speed. But, only on the top graph (turn 6) is the red lap faster. You can also see the red lap's minimum speed (therefore throttle application) comes later in both graphs because of that increased entry speed.
You will notice that on both laps the red line gains time on the black lap on the corner entry. In the entry speed corner, the following "straight" is very short so the black lap simply can't make up for the time lost on entry by getting back to throttle and full throttle earlier.
But, when we increase the length of the acceleration zone out of a corner it's a different story and the black lap is all of a sudden faster.
