Woot! Thanks. It seems at the point I’m at on the track I’m working on, it’s all subtle gains from finding a bit more exit speed.
Even if you switch up your perspective from % throttle to % tire load/traction, you could still argue that, in general, 50 -> 100 is preferable to a constant 75 because when you drive with a constant throttle you are surrendering the opportunity to influence how energy flows in you car longitudinally (and therefore where, when, and how that energy creates loads in your tires). For example (excluding lateral forces for simplicity/clarity):
Constant 75% Throttle
If you approach a turn, roll back to 75% throttle and turn in, then when initiating the turn there is effectively very little longitudinal energy on (or being transferred to) the front end, which can limit the amount of speed you can carry at the turn-in point. As the turn progresses, the act of turning (the scrub and/or energy required to generate and maintain slip angles) does gradually (or cyclically) transfer more energy longitudinally to the front end until the energy reaches is peak at the turn’s apex/rotation point. Then that energy gradually rebounds from the front end and travels longitudinally to the rear end… producing the load/traction you need to complete the turn.
In this scenario the longitudinal energy movement in the car is very slow and subtle, because it is being left up to ‘nature’ (the combination of speed, corner radius, track/tire interaction, etc.) to determine when, where, and how energy moves and tire loads are created. The other potential issue is that since longitudinal energy moves so slowly in this scenario, the required transfer of energy/load front to rear at the critical moment when the car rotates at the apex happens very slowly. So, for a moment neither end of the car has the load it needs for optimum traction (a concept which TJ mentioned above). To summarize; constant 75% throttle produces a relatively unloaded entry and a relatively slow longitudinal energy transition at the rotation point, both of which can cost you speed/time, and both can also impact your confidence due to the ‘unloaded’ feel they produce.
Varying throttle from 50% to 100%
In this scenario, you are using the throttle to take control of how longitudinal energy move through your car and produces tire loads/traction. If you roll back the throttle to 50% (instead of 75%) you are effectively doubling the amount of longitudinal energy on (or being transferred to) the front end, which means you should have a relatively more loaded/planted front end for turn-in, which means you should be able to turn in with more speed/confidence. As in the 75% version, energy builds gradually/cyclically, but this process started with more energy (a bigger longitudinal ‘push’), so the energy builds to a peak a little more quickly, meaning that the ‘rotation’ point occurs a little earlier than the actual ‘apex’ of the turn.
Since there is more energy momentum at play when the car rotates, it will do so more aggressively. Therefore you must use the throttle to take control of transferring the energy needed to manage the rotation to the back end (instead of just letting the natural energy ‘rebound’ do so like in the 75% approach). So, you begin rolling on throttle, which continues to feed energy to the rear end, which builds slip angles to their peak and maintains them longer, which slightly alters your trajectory out of the turn, which lets you carry/build more speed out of the turn.
All that said, written out, these two approaches seem quite different, but in reality, the differences are very, Very, VERY subtle. But ‘subtle’ is where the 1/10s hide.
Ok that makes sense. So the act of squeezing it in does feel more stable. It’s not unstable at 75, but it’s potentially unstable. The acceleration through does hunker car down in comparison.
This is interesting stuff. I love Lewis shooting analogy, and the eye tracking is a close look at what the best guys are actually doing at the wheel.
If you’ve found any more of this kind ion thing, I’d love it if you’d post it here.
Thanks for sharing.
Great example of this is at GKVC? Kart track in kart Kraft. There’s a left sweeper at the end of the back straight. The turn can be taken in the traditional manner, brake, turn, go. However, you can simply throttle, lift, throttle. If you time the throttle pause correctly (it’s short) and then floor it, the induced understeer from the weight transfer and subsequent accel flies the kart through the turn 3-5 mph faster. There’s not many people playing, but as I climbed my way up the leaderboard in TT, this was the corner I’d pull on the ghosts easily.
2 turns later is the opposite. Uphill corkscrew left. This is one of those turns that trying to have throttle input going through the kart will kill your momentum. Sometimes you just have to be patient and wait for the kart to turn before trying to get in throttle.
So far I have learned that yes, generally trying to get in throttle as early as possible, with as little brake as possible is a good way to go about things.
But, there are some pretty big exceptions. You do need to flow kart through some turns, and as such, some turns do not allow you to accelerate trough them until the kart comes around. These turns require patience. The window for earlier throttle is there, it’s just a longer wait for it.
Dom that’s exactly how we take that turn at GVKC in real life too, just lift for a moment at the turn 2 left and if you hit it just right and get back on the gas you scoot right through the S that follows… didn’t know they had our track in Kartkraft — even more excited for the console release now, sounds fairly accurate. The corkscrew monza turn after has a couple lines, still trying to figure out the best there; all I can figure out is run wide at the exit
Wow! Great to know thanks. It’s kinda the same as turn 1 at etown but with a lift.
That uphill turn is brutal with the current physics build. So little steering input required. It’s almost as if you have to let the kart turn itself.