"If I had more time, I would have written a shorter letter." - Blaise Pascal
This post will focus on the physics
(read: fiziks) and car side of development and expand a little on the changelog. Plenty has been done for 0.4 that I'll go through in this post.
The
Ferrari SF-25 needs and will receive its own sticky thread.
Tire Damping
In 0.3 we introduced a higher frequency for the Suspension of 1000hz. On top of that, we have developed a new method for inherent tire damping, the lack of which seems to have been a root cause for ACC's bouncing issues and hopefully you should not see this again. The tire will now rarely really lose contact with the ground. This took quite some R&D and is part of the physical foundation of this update, making bumpy tracks like the Nordschleife, Oulton Park or Road Atlanta a pleasant experience even in very stiff cars.
Tire Inertia
We adjusted the tire inertia to better match each car's individual tire dimensions. For example, you will notice this when braking with the non-ABS Porsche Cup. The tire now has more inertia and thus is harder to lockup. At the same time a tire with more inertia is harder to spin up on power, so when you are going into a slide, the engine won't as easily rev up to the limiter - ultimately allowing better control in post peak grip situations.
Cars "stuck" in Understeer
We went down the rabbit hole of finding the root cause of RWD cars refusing to rotate on power without deliberately and forcefully breaking traction. For that we worked on two things: Combined grip and the slip ratios.
Essentially slick tires now have more baseline grip both laterally and longitudinally, but less additional grip in combined scenarios (e.g. braking + turning, or turning + accelerating). You will still have high corner speeds, better traction and deceleration, but the car will be more sensitive especially at initial throttle pickup until you are able to open the steering and then plenty of grip is available. It's quite nice to work with that. The rear will be playful, but not deadly, while also not allowing you to abuse sliding as you'll lose time and overheat the tires. Aggressive driving might pay off on a Q run, but not in a race (until someone proves the opposite...).
However, without also looking into slip ratios, the above change would not have been enough to address the inherent understeery nature. Upon open heart examination we came to the conclusion that the rear tires produced a bit too different slip ratios due to too optimistic assumptions of load related tire diameter changes. Something simple on the surface, but with large consequences throughout the entire grip calculation. This led to the inside driven tire producing more longitudinal force than it should in critical scenarios like corner exits. This force worked directly against the request of the driver to rotate the car.
Actually, there is a third component here that we want to address in the future around the overall morphing of the curve defining slip ratio related grip. Though, this has to wait for now and the expected impact is not as major as the above changes we made.
Tire Pressures, Wear and Temperatures
While further revisions and adjustments are likely, here's where we currently are on that front.
Tire wear has generally been increased. For all street legal compounds this is hardly a factor unless you drive really long. They generally produce the same grip over a long period of time. In future updates we'll make them wear faster when overdriving severely.
Road and slick tires are so far also not very sensitive to the theoretical optimal pressure, or rather
not having optimal pressure. This will also be addressed in a future update.
The same is true for tire temperatures, with all road compounds being rather insensitive and having a wide operating window.
The reason for both is: Our model has become quite complex with a ton of parameters and really dialing in their relationships takes time (that means long periods of undistracted testing in night sessions). This has been done extensively on the
SF-25 where you can see much more alive tires and all other compounds will benefit from these learnings in the future. There is/will be a separate post on SF-25 tires in the car specific thread.
Ideal Tire Pressures:
Road & ECO: 31.0 PSI
Supercar: 30 PSI
Hypercar: 29 PSI
Slicks: 27 PSI
SF-25: 25 PSI
Car Electronics: TC & ABS
We have reworked the TC and ABS logics on every car.
Our system allows to separately define the response of the TC intervention among a variety of Parameters:
- Slip Ratio
- Slip Angle
- Angular Speed of the rear end
- Oversteer
First of all, most TC levels will now allow more before stepping in. They will also act less rude. Some levels on race cars in particular will mostly engage due to slip ratio and slip angle, but almost ignore angular speed and oversteer (i.e. the driver counter-steers). Only on higher TC levels these factors will be considered and the TC will step in at earlier.
Ultimately, this should allow you to play with the car without TC interfering, but at the same time give you the confidence to explore the limits.
In the future: More noticable TC & ABS related sounds across all cars.
ABS has also been revised. Generally our system was too perfect, operating at too high frequencies, having it too easy controlling the tire in too tight margins. The operating frequency has been lowered, while the window of its engagement has been widened. Additionally, there have been adjustments to how independent each tire can be controlled individually by the system. Especially on older cars more imperfection should be noticable.
Since this is a vast update, please report any bugs you might come across.
He divides opinions but I actually like the guy.
traxion.gg
