Cars (DATA REPLACEMENT) Nissan Skyline R34 GT-R V-spec Improved Physics by Arch

[jlnprssnr]

Hey Kyuubeey, sorry if this is offtopic, but do you mind sharing some of your ATESSA wisdom in this thread by a BeamND.Drive dev? https://www.beamng.com/threads/crowd-sourced-research-active-differentials.71205/ I tried to type something up but it's so damn complex, the more I read, the less I understand, haha

 

[Kyuubeey]

I'd rather just tell them to go find the SAE paper for the system than to be held accountable for anything incorrect I might say. Don't exactly wanna contribute to the already massive misconceptions having to do with the system and GT-R's in general.

 

[Kyuubeey]

Kyuubeey updated R34 GT-R V-spec Scratchmade Improved Physics by Arch with a new update entry:

Electronics, suspension, aero, tires, misc

07.07.2020 Version 2.6

- Added roadspeed control to ATTESA to account for limitation, thanks @baker7498
- Removed incorrect controller entries from ATTESA
- Redone rear suspension geometry
- Adjusted rear bumpstops
- Adjusted front geometry based on new data
- Adjusted aero
- Differentiated DX and DY load curves in tires
- Tire tweaks
- Raised gain on S3 ATTESA LonG controller
- Lowered S3 rear diff power lock
- Changed graphics options (Camera, exposure etc.) in car.ini closer to KS...

Read the rest of this update entry...

 

[AlexR32]

I'd rather just tell them to go find the SAE paper for the system than to be held accountable for anything incorrect I might say. Don't exactly wanna contribute to the already massive misconceptions having to do with the system and GT-R's in general.

This SAE paper?

SAE MOBILUS

saemobilus.sae.org

Or is there a better one?

 

[Kyuubeey]

This SAE paper?

SAE MOBILUS

saemobilus.sae.org

Or is there a better one?

I can't remember which one it was, I've taken a look at one but I've lost it.

Made some decent progress on the overall Nissan chassis over the last week. Found some hard data which I trust.

Currently the GT-R is, believe it or not, actually a bit too nervous and hard to drive. Somewhat closer to what it should be with that data put in. Running out of things to update however.

 

[AlexR32]

I can't remember which one it was, I've taken a look at one but I've lost it.

Made some decent progress on the overall Nissan chassis over the last week. Found some hard data which I trust.

Currently the GT-R is, believe it or not, actually a bit too nervous and hard to drive. Somewhat closer to what it should be with that data put in. Running out of things to update however.

The SAE paper is pretty good and you can access for free via JSTOR btw. It explains principles but not values and in some scenarios the "gain" is very small e.g. the engine braking/abs effect, is barely detectable even on track. Due to the date it probably relates to the R32 system and things had evolved by the R34, so it may not be complete for the R34.

You may be aware but a popular modification is to allow the driver to attenuate the lateral g sensor output to give the impression of running on a lower mu surface and increase the transfer case clutch response speed and magnitude. Looking at logged data it is surprising how little 4wd is used without this modification. It makes it much more forgiving.

Something else not covered in the SAE paper is that the R32 ran at 0 clutch pressure until called on and this resulted in up to a 500ms delay before torque transferred to the front wheels. This is part of the reason for the characteristic big slip angles you see in video of R32s. The 33 and 34 addressed this by running a constant base pressure on the clutch pack, this speeds up the response but also means they were never fully rwd like a 32.

The "Fast start" feature is mentioned in the paper but not explained. Essentially it just looks for >60% throttle opening when stationary and pre-pressurises the clutch ready for a launch.

I have some some logged R32 GTR data from Silverstone if that would help (17mb csv). It has 4wd clutch line pressure and long/lat g and throttle position (no wheel speeds sadly, which according to the sae paper is at least half the picture).

 

[Kyuubeey]

The SAE paper is pretty good and you can access for free via JSTOR btw. It explains principles but not values and in some scenarios the "gain" is very small e.g. the engine braking/abs effect, is barely detectable even on track. Due to the date it probably relates to the R32 system and things had evolved by the R34, so it may not be complete for the R34.

You may be aware but a popular modification is to allow the driver to attenuate the lateral g sensor output to give the impression of running on a lower mu surface and increase the transfer case clutch response speed and magnitude. Looking at logged data it is surprising how little 4wd is used without this modification. It makes it much more forgiving.

Something else not covered in the SAE paper is that the R32 ran at 0 clutch pressure until called on and this resulted in up to a 500ms delay before torque transferred to the front wheels. This is part of the reason for the characteristic big slip angles you see in video of R32s. The 33 and 34 addressed this by running a constant base pressure on the clutch pack, this speeds up the response but also means they were never fully rwd like a 32.

The "Fast start" feature is mentioned in the paper but not explained. Essentially it just looks for >20 throttle opening when stationary and pre-pressurises the clutch ready for a launch.

I have some some logged R32 GTR data from Silverstone if that would help (17mb csv). It has 4wd clutch line pressure and long/lat g and throttle position (no wheel speeds sadly, which according to the sae paper is at least half the picture).

Hey,

I didn't know lateral G modification was also actively done, but I did suspect it because some kits allow a gain control on it. LonG doesn't seem to cut it when trying to match something like the Mine's car. That's good info, thanks.

R32 case didn't run at 0 pressure IIRC, just less. 33 and 34 internal pressure was increased for faster response speed, however it did not mean they were always transferring torque. That seems to be a bit of a myth perpetuated for a few decades now and anyone who tunes the cases told me that it's just to allow for faster response. The extra pressure in the case isn't even enough to transfer any torque IIRC. If you want you can push it even more than the 33 and 34 did.

You can get near-instant response even out of 32 cases, but it doesn't mean there's a "constant 5% transfer" or whatever else people make up. But that's just what I was told.

It's a bit difficult to simulate the response time accurately because there's no actual lag value , I'd have to use heavier filtering which is...not the same thing, so I've opted to just take what I can get. R32 drives very good on-video out of corners so I'm not super concerned.

If you would like to send me that file, drop me a PM, I'd gladly take a look at it.

At this point I have most of the curves already and it's more of an implementation method limitation thing, but data is always nice to have.

PS: Would you happen to know how much power R34 or R33 RB26's make? I have a very good suspicion that the current power output is much too low, perhaps even 20, 30ps. It's closer to an R32 than anything.

 

[AlexR32]

Sorry, you are right the R32 wasn't 0, now I remember it. It would see around 1 bar "static", probably just enough to pre load the clutches, the later cars run maybe twice that as I understand it. Which is enough to change the balance of the car slightly, in my experience at least.

I think the factory themselves tuned the ATTESA "qualitatively" so there's no shame in tweaking your config within the limitations of AC's physics to get it to feel right.

When it comes to qualitative tuning the HICAS makes for some odd feelings at/over the limit, the R34 HICAS is much better though than the R32 which usually have HICAS removed for track use.

For sure, a stock RB26 makes more than the rated 280. R32 and 33 tend to dyno well over 300bhp. A little more if you run 1bar boost by removing the restrictor in the wastegate control line. The R34 had different turbos and camshafts and made a little more again. 350bhp at the flywheel would be a reasonable estimate. You'll see stock R34 dyno figures at the rear wheels up to 300bhp or at all four wheels 280bhp. Late Vspec2 Nur makes a little more again I think.

I will PM you the data.

 

[Dr.Needlefingers]

The brakes lock very easily with the latest version after cresting Quiddelbacher Hohe at Nordschleife. The brakes actually stay locked after completely releasing brakes with S2. Any ideas how to fix this? Ive changed damping settings and alignment around. Version 2.4 does not seem to have this problem.

 

[Kyuubeey]

The brakes lock very easily with the latest version after cresting Quiddelbacher Hohe at Nordschleife. The brakes actually stay locked after completely releasing brakes with S2. Any ideas how to fix this? Ive changed damping settings and alignment around. Version 2.4 does not seem to have this problem.

The fix is to not brake in mid-air. The wheels won't continue rolling until they hit something, so it's basically the same as a lockup when you touchdown.

 

[Dr.Needlefingers]

That does make sense. I would say that I imagine the effect to be overstated so far as the duration and severity of the lockup without brakes even being applied upon landing goes. Again, the issue doesn't seem to be as pronounced as any Kunos car or any of your other fantastic physics mods. I could provide a video of what I am referring to if you like, otherwise I am just as happy with version 2.4.

cheers

 

[Kyuubeey]

That does make sense. I would say that I imagine the effect to be overstated so far as the duration and severity of the lockup without brakes even being applied upon landing goes. Again, the issue doesn't seem to be as pronounced as any Kunos car or any of your other fantastic physics mods. I could provide a video of what I am referring to if you like, otherwise I am just as happy with version 2.4.

cheers

Probably negative lonG torque is causing a bit more lockup than you'd expect, but personally I've never ran into any real issues.

If you apply brakes *during* being in the air, the wheel will remain stationary until you hit the ground. It doesn't matter if you're braking during landing.

If you can be bothered to, take some video from outside the car.

 

[lazcoder]

Can we use this mode on online servers? Or is there an online server using this mode?

 

[Kyuubeey]

Can we use this mode on online servers? Or is there an online server using this mode?

Nothing is stopping you from using it online. Not sure there are any servers running my cars. They're a bit too difficult to DL for people to be motivated to host a server, I think.

 

[lazcoder]

It would be nice if there was an intermediate version of ~500 HP

 

[Kyuubeey]

It would be nice if there was an intermediate version of ~500 HP

Well you're gonna be disappointed with the next release, because I'm removing all of the S-versions. They're too much work to maintain and just cause people to ask for more, like you just did.

 

[lazcoder]

Well you're gonna be disappointed with the next release, because I'm removing all of the S-versions. They're too much work to maintain and just cause people to ask for more, like you just did.

This was sad. Obviously I am satisfied with the existing versions.

 

[Kyuubeey]

This was sad. Obviously I am satisfied with the existing versions.

The old ones will still exist in the "history" section, but it's a bit too much to take care of 3, 4 versions of already soon over 30 cars. In RD alone I think there's about 10 unique cars with an average of 2 or 3 versions per car.

It's either that, or no updates at all. The only way to keep it manageable is to only maintain a few important ones. I understand why KS themselves just stopped doing tuned versions after some time.

 

[lazcoder]

The old ones will still exist in the "history" section, but it's a bit too much to take care of 3, 4 versions of already soon over 30 cars. In RD alone I think there's about 10 unique cars with an average of 2 or 3 versions per car.

It's either that, or no updates at all. The only way to keep it manageable is to only maintain a few important ones. I understand why KS themselves just stopped doing tuned versions after some time.

R34 deserves attention. Good luck and we are grateful to you for making this mod.

 

[Kyuubeey]

Kyuubeey updated (DATA REPLACEMENT) Nissan Skyline R34 GT-R V-spec Improved Physics by Arch with a new update entry:

CSP stuff, ATTESA, tires, suspension

15.02.2021 Version 2.7

- Special thanks to @abbo90 / Giuseppe Abagnale and @baker7498 for help with ATTESA
- CSP version 0.1.68+ required, 0.1.72+ recommended
- Removed S versions to ease development
- New CSP Extended Physics heating for tires and brakes
- New CSP Extended Physics tire features for slip, self aligning torque, camber etc.
- New CSP Extended Physics suspension features
- New logic for tire load curves, combined grip
- Updated front geometry selection; for mod makers
-...

Read the rest of this update entry...