Driving Simulator - Rolling Off the Brakes
The previous case makes it obvious that combining acceleration with cornering produces a quicker sector time. The racing line also moves inside the reference line. Rolling off the brakes while turning into the turn combines deceleration and cornering.
Rolling on the throttle and rolling off the brakes (trail braking) are similar processes. Rolling on the throttle occurs during acceleration and cornering. Rolling off the brakes occurs during deceleration and cornering. If you ran a corner backwards, you’d simply be reversing the two processes.
At the turn-in point in this example, the driver decides to reduce braking and add steering. He continues to reduce braking and add steering for one second. This reduces his speed 12.075 mph before he begins to roll through the turn at a constant speed.
The driver will then decide to go to the throttle with 30 degrees remaining at the turn. This produced a 13.299 sector lap time. But by combining deceleration and cornering for the first second (about the first 25 degrees of the turn, the sector time is lowered to 13.143 seconds, which is quicker than the best acceleration-only time. The exit speed is 110.711 with a minimum speed of 61.170 mph. The inside apex is near the middle of the turn.
The Braking point is at 370.1 with the Turn-In at 68.3 feet and 73.245 mph. This line permits later braking (other than the extreme #4 line) but the Turn-In point is much earlier and at a higher speed. This is because much of the deceleration occurs after the Turn-In point.
Drivers often learn to roll off the brake by getting to the turn-in point with too much speed. They react by beginning their cornering at the desired turn-in point and continuing to slow as they enter the turn. To their immense relief they discover they can survive the mistake and also reduce their lap time. A trail-braker is born.
Rolling off the Brakes Even Sooner
If we increase the braking to 3.0 seconds (36.2 mph) the sector time falls to 12.649 seconds but the exit speed declines to 113.644 mph. The minimum speed is 56.115 mph and the apex is at 58 degrees.
#
Acc/Dec Sector Time/Speed Ext-1
Time/Speed Ext-2
Time/Speed
1
0/ 0 13.616 106.939
23.384 163.570
33.003 187.801
2
30/ 0 13.299
110.734 22.925
164.567 32.508
188.209
3
60/ 0 13.144
114.684 22.623
165.668 32.167
188.663
4
75/ 0 13.300
117.066 22.691
166.363 32.211
188.951
5
30/1.0 13.143
110.711 22.770
164.561 32.354
188.206
6
60/1.0 12.974
114.598 22.456
165.643 32.001
188.652
7
60/2.0 12.807
114.262 22.302
165.548 31.851
188.613
8
60/3.0 12.649
113.644 22.166
165.372 31.721
188.540
Notice that the quickest sector times occur in the last run. The fastest exit speeds are on line #4 with the exaggerated late apex but these do not translate to quick laps, even with a 5,000 foot exit straight.
The Diamond Line
All of the previous examples suggest the slower the minimum speed the quicker resulting sector time. Yet we are approaching the limit of the inside radius speed.
But nothing says the inside apex must be clipped during the roll-through portion of the time. Examples 3 and 4 (accelerating from 60 and 75 degrees). We can do the same thing by selecting an apex 3 feet off the inside radius and a speed of 52.0 mph.
This line produces a sector time of 12.553 seconds, our best yet and an exit speed of 114.421. This is often called a Diamond line in the oval track world. It usually applies to 180-degree turns and is rarely relevant with 90-degree road racing turns.
#
Acc/Dec Sector Time/Speed Ext-1
Time/Speed Ext-2
Time/Speed
For the results of the Diamond Line you need to consult the Driving Simulator.