Why minimum preload works in ACC
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- Опубликовано: 30 сен 2024
- In depth analysis on why setups for Assetto Corsa Competizione use the minimum amount of differential preload
0:18 how does a differential work
6:00 why does minimum preload work in acc?
8:05 driving exaple acc
10:33 motec analysis
12:50 2 tires on the grass test
#ACC #assettocorsa #assettocorsacompetizione
Nice vid, I think your audio is very quiet compared to other YT videos though.
Excellent explanation and video. Fully agree Kunos needs to work on the diff simulation and also the aggressiveness of the engines. One needs almost 40% throttle before the cars hit the limiter. Everyone is complaining that the TC doesn't work but it is because of the diff simulation and the flat throttle response that the TC seems broken.
I think there are many reasons for the current TC off meta. The diff giving you the best traction at the lowest setting surely contributes to that as well. The problem with the throttle response is that no one really knows how the engine behaves on partial throttle application. This is because modern cars all have an electronic throttle valve, which means that throttle input does not correlate 1:1 with the angle of the throttle valve, but instead the ecu controls the throttle valve based on a given value from the throttle position sensor. With the calibration of the ecu, a lot of the non-linearity between throttle valve angle and air pressure inside of the intake (and thus power) will get cancelled out as the ecu opens the trottle valve only slightly in the lower part of throttle input and much more rapidly in the higher part. It can even go as far as making the throttle input 100% linear to power output of the engine. But unfortunately afaik the cars haven’t been dyno‘d with a partial throttle application and thus no one really knows how the engine behaves in this part.
This guy deserves more likes. Keep up the good luck, my man!
When explained with a German accent technical stuff like this immediately makes sense to me.
😅
So you're telling me, that all this time, I've been getting snap oversteers because I'm running around with ~70-100Nm Pre-Load?
The full Nurburgring got released and I've spent nearly 5 hours just to get a single clean laptime down because of the sudden spins from phantom bumps... And all because of my Pre-load Diff... Should i go cry myself to sleep?
It doesn’t necessarily have to do with the preload. Using minimum preload will make the car more stable on low speed corner exit. But if bumps are your problem, it probably has more something to do with your suspension setup.
Just because the minimum preload works well in some cars, does not mean it always has to be the best way to set up the car. Some cars take it better than others. For example, i would pretty much always use minimum preload for cars such as the aston gt3 and audi gt3, but there are also cars like the porsche gt3 that like having a bit of preload.
Basically, just try out what works the best for you. The way the diff setting affects the driving behaviour is quite complex. But as a rule of thumb, you can go by the following rule: More preload will make the car more oversteery on throttle and more understeery off throttle. Less preload will make the car more understeery on throttle and more oversteery off throttle.
If you want to try out an existing setup for the Nordschleife, i’ve seen @Fri3d0lf has made a free setup for the Ferrari 296. I haven’t tried it, but usually his setups are quite good and easy to drive, so you can give this a try.
Also the Nordschleife is very difficult to drive and it takes an insane amount of time until you can drive consistently there. Just keep practicing and eventually you’ll figure out where all the bumps and tricky places are.
@@seydlitz_racing hey I'm diving the 911 and when you say some preload, what exactly do you mean? I have some tunes that run it pretty low(60) for faster tracks, but find it feels good to run it higher on tighter tracks(150-200), but I'm also not great at tuning plus I'm new to sim racing. I just find it to be a lot of fun to try and figure this stuff out. I haven't really gotten to suspension tuning yet because it's so in depth. I'm also seeing a lot of people saying you need to run motec or something similar to really get into the suspension aspect, is that true in your opinion, or do you think trial and error is enough?
@@ihavealife002 Well first of all, I can’t give you specific values for the preload of the Porsche. There is no „meta“ value that works the best. There are lots of different setups out there, making different kind of values work. It also depends on the track and driver preference.
The reason why Porsche setups often not use the minimum preload, is because it can reduce lift-off-oversteer and the Porsche has a tendency to sometimes have a bit too much of said oversteer.
In order to set up the preload correctly, trial and error is definitely the right approach. This is because 1) the way the car’s behaviour changes when changing the preload, often does not correlate with how it should be in theory (like i explained in my video) and 2) because the preload is purely one-dimensional and does not depend on any other setting inside of the setup. So just try out different values and keep what feels the best to you.
Now to the suspension. We have to separate here between the page for the mechanical grip and the page for the dampers. Understanding the dampers and damper tuning is *way* more difficult than the mechanical grip. For the beginning, the damper tuning is not _that_ important, so you should focus on understanding the mechanical grip first.
The MoTeC tool you were referring to is called MoTeC i2 pro and is a data analysis tool that can be used to set up the dampers. But you definitely don’t need it to set up the mechanical grip, so don’t worry about it for now. I will make an in depth setup guide in the future where i will explain in detail how each of the settings work and how you can use them to make the car do what you want.
@@ihavealife002 Motec is only necessary for damper tuning, u can fiddle with suspension no problem, I often don't even have to change dampers with small tweaks.
I think it makes more sense if you keep in mind that ACC simulates a clutch-type limited slip differential. Going on full throttle will lock up the diff, turning it into basically a full locked differential.
Engineering explained has some nice videos explaining this. I hope you don't mind I put two links to them here:
ruclips.net/video/ujsxq9WBllU/видео.html
ruclips.net/video/6DmItXixE30/видео.html
Yeah you’re right, but you are still adjusting how much the differential is locking under acceleration with the preload setting. So in theory a very low preload should give you bad traction out of the corner. But in ACC it is the other way around. With the lowest amount of preload, you are getting the best traction. If the Diff was was always fully locked under acceleration and always fully open off throttle, then the whole preload setting would be pointless.
@@seydlitz_racing It's other way around. Pre-load applies a base amount of pressure on the clutch plates. So, it is adjusting how much the diff locks when not on throttle. Also, in higher gears, driveshaft coming from gearbox will apply lower torque and higher pre-load values can actually have more of an effect. In lower gears, the torque from driveshaft will be the dominant force and on throttle the diff will fully lock. Even fully locked there can still be a little bit of slip though. But this is not tunable in ACC setup.
@@femkeligtvoet8896 But that's exactly how the cars not behave like in ACC. Changing the preload will massively affect the way the cars behave on throttle. You can watch the video from Aris on the differential in ACC (ruclips.net/video/jBRUfI-rB-Q/видео.htmlsi=S_Z3JmAJgbqOizs7). In that video he explains how the preload affects the cars behavior on throttle. In his driving example he had too much oversteer on throttle and as a countermeasure he decreased the preload.
The reason why I even dealt with this differential topic is because a few months ago, i was testing a setup for the Aston at Kyalami. I started with minimum preload and for the TC i was using 2-0. I then changed the preload to somewhere between 100-150 N/m and all of a sudden I was massively struggling on low speed corner exits. The rear would just step out every time i went on throttle and i had to use a higher TC level than with the minimum preload. As someone who drives an open diff car in real life (the traction on corner exit is absolutely terrible), this got me thinking about how that even makes sense.
I hope you can understand my point here. Since lower preload will make the car more stable on low speed corner exit, this means that less of the engines torque is delivered to the outside tire (which is mainly responsible for keeping the rear in line with the front of the car). However this would also mean that with a low preload you would have bad traction out of these corners, since the torque is mainly delivered to the inside tire with less grip available. But in ACC, the cars have perfect traction, even on the lowest diff setting. That's basically the whole point of the video.
@@seydlitz_racing "However this would also mean that with a low preload you would have bad traction out of these corners, since the torque is mainly delivered to the inside tire with less grip available"
Bad longitudinal traction, but not bad lateral grip! Because with an open (or low lock) diff the inside tire will start spinning when the outside tire is nowhere near its limit, you will retain more lateral grip at the limit of wheelspin. More locking (or more preload) means more power oversteer due to more even use of the tires, but also more peak acceleration mid corner since, as long as you dont power oversteer, the outside tire can be doing more work towards accelerating the car.
@@whysoslow1999 Yeah exactly. Have I said anything different? 🤔