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How to adjust setups for GT3s in v1.9?

Discussion in 'Chit Chat Room' started by Strummer, Oct 28, 2016.

Page 9 of 10

DuckeyTapey Hardcore Simmer

PhilS13 said: ↑

With V10 also came an adjustment on that so it's not true anymore. It used to be aim for optimal no matter what but now you can really use pressures to adjust temps without losing lots of grip.
Click to expand...

Oh yeah, forgot that. I didn't bother testing it since straying away from optimal pressures would affect grip so much, might try that now. Would be interesting if you can improve grip for those tyres that are running too hot or too cold.

DuckeyTapey, Nov 24, 2016

#161
ACJJ619 Racer

So basically, until now it's been fairly pointless using tyre pressure to adjust temps?

ACJJ619, Nov 24, 2016

#162
Kade Hardcore Simmer

ACJJ619 said: ↑

So basically, until now it's been fairly pointless using tyre pressure to adjust temps?
Click to expand...

Absolutely pointless.

Kade, Nov 24, 2016

#163
DuckeyTapey Hardcore Simmer

ACJJ619 said: ↑

So basically, until now it's been fairly pointless using tyre pressure to adjust temps?
Click to expand...

Yes, although the only mention of it in the changelog is way back 1.7 from July. Weird that I didn't see anyone mention it before, considering it being something that people used to criticize about the tyre model, maybe I missed it. It might also have been adjusted with the following updates though.

DuckeyTapey, Nov 24, 2016

#164
Andrea Mantovani Rookie

Georg Siebert said: ↑

Believe I can help you with this,
the 488 GT3 has inherently more understeer than other cars in its class, an attribute which got only amplified with the new v10 tyre model. The new tyres feel stiffer, have a more detached road feel, loose grip with slip angle sooner and a pressure varience (e.g. due to temperature rise and fall over a lap) has less of an effect on response and handling of the car. On top of all that, the downforce of the 488 GT3 was nerfed, so less aero grip as well. Let's go through some remedies, shall we.

Setup adjustments in order of importance/effect on car
1) spring rate & ARB
2) tyre pressure
3) camber & toe
4) aero
5) dampers
6) differential & electronic aids
7) others

Pre-flight checks
- make sure to have ENABLE_DEV_APPS=1 in system/cfg/assetto_corsa.ini
- enable car engineer
- enable aero app

Spring rate & dampers
- the default spring rate with 130 kN/m on the front is too much for a mid-engined, mid-downforce car like this, a higher spring rate in the front just increases the car's understeer -> lower it to 110kN/m, we get a nice 3.3Hz/3.2Hz ride frequency distribution between front & rear axle
- the four damper values below are damping ratios, the ones for the front axle are accurate, the ones for the rear are not (a timeless bug it seems)
- a damping ratio of 1 equals critical damping, the 488 has a 'normal' damper layout, so we want to stay below a ratio of 1
- we want the front rebound to be higher than the bump, that helps agility and transient response (S-curves, Les Combes)
- as mentioned, the rear ratios are wrong, if the damping ratios (front & rear) lie between 0.5 and 1, the correction factor is 0.25, if the ratios are higher than 1, the correction factor is higher as well, so it is not constant (not intuitive, I know)
- so at default the front bump ratio is 0.87, the rear displays as 0.81 - the correct rear bump ratio is then ca. 1.15, hence too much
- so increase rear rebound, decrease rear bump and increase rear rebound to bring it in line with the rear bump

ARBs
- since the actual value is not displayed, this limits our understanding and recommendations of this item
- suffice it to say, a one click adjustment on the front ARB has a higher effect on handling than one click at the rear on this car, this applies to GT3 cars in general
- since we decreased the front spring rate, we have to compensate with +1 ARB_FRONT to retain the absolute roll stiffness and its distribution between the front and rear axle
- if the car still understeers, then increase ARB_REAR

Tyre pressures
- the optimal pressure for GT3 tyres (even in v10 as far as I can tell) is 33 psi
- as anecdote, was driving a custom GTLM car on Spa yesterday for which optimal pressures are 35 psi, difference between 33 and 35 psi on this car was 0.7x seconds a lap
- the default cold 25 psi should rise to the desired 33 at 80 degrees, if front or rear tyres are below that through most of the lap, increase pressures accordingly

Height
- set ride height to lowest possible, to 0, you won't have issues with the minimal requirement
- benefits: a lower cg for faster transient response, a slightly higher CL (coefficient of life (freudian slip, lift)) from front splitter and diffuser
- the actual ride height is not the one displayed in the car status, look for it in the aero app, GH (ground height) in yellow for front splitter and diffuser
- the actual collider of the car model has a seperate height value from the cg, in the physics files

Aero
- at the bottom of the aero app, you'll find the sum of the lift & drag coefficients and the total downforce and drag values in kg
- the calculations of this app only work during driving and not during replays
- an increased AOA (angle of attack) of the front splitter has nearly no drag penalty, for maximum downforce adjust only the rear wing for the following point:
- look at %@front, have it between 46 and 49% for a balanced aerodynamic load on the front and rear, anything above 50% is inherently unstable, this value will fluctuate whilst driving, so make some screenshots to look at it more closely on the desktop

Camber & toe
- the default rear toe is way too positive, resulting in more understeer - I personally am a big proponent of toe values of 0, a seperate topic, so take these as you like
- set toe to or close enough to 0, better to have it positive than negative at the rear, +/- 0.02 radiants in the front are ok
- as mentioned above, the grip decreases with increased slip angle slightly sooner in the new v10 tyre model than with v7, so make the static camber angle a bit less negative as pictured below
- static camber, because the camber angle fluctuates during cornering - more negative camber leads to a higher slip angle (see suspension app, purple SA value for more details)
- in general, anything more negative than -3.4 degrees is too much for these GT3 tyres (v10, v7, v6)

Differential
- lower DIFF_COAST to 40% for more turn-in, if unstable under braking increase to 50%

Traction control
- the default setting when you load the car is not setting 1 on the traction control list
- TC is defined in the physics files as slip ratio limit, say 0.11 - hence if this ratio is reached, the TC will kick in - the higher the TC setting (CTRL+T), the higher the slip ratio limit, the less restricting it is
- increase TC, if you have understeer out of corners - a too high setting will result in oversteer of course
- all above points apply to ABS as well

That's it for now, have at it.
Gonna make some food now, tortelloni with broccoli and zucchini.
Click to expand...

Georg Siebert said: ↑

Believe I can help you with this,
the 488 GT3 has inherently more understeer than other cars in its class, an attribute which got only amplified with the new v10 tyre model. The new tyres feel stiffer, have a more detached road feel, loose grip with slip angle sooner and a pressure varience (e.g. due to temperature rise and fall over a lap) has less of an effect on response and handling of the car. On top of all that, the downforce of the 488 GT3 was nerfed, so less aero grip as well. Let's go through some remedies, shall we.

Setup adjustments in order of importance/effect on car
1) spring rate & ARB
2) tyre pressure
3) camber & toe
4) aero
5) dampers
6) differential & electronic aids
7) others

Pre-flight checks
- make sure to have ENABLE_DEV_APPS=1 in system/cfg/assetto_corsa.ini
- enable car engineer
- enable aero app

Spring rate & dampers
- the default spring rate with 130 kN/m on the front is too much for a mid-engined, mid-downforce car like this, a higher spring rate in the front just increases the car's understeer -> lower it to 110kN/m, we get a nice 3.3Hz/3.2Hz ride frequency distribution between front & rear axle
- the four damper values below are damping ratios, the ones for the front axle are accurate, the ones for the rear are not (a timeless bug it seems)
- a damping ratio of 1 equals critical damping, the 488 has a 'normal' damper layout, so we want to stay below a ratio of 1
- we want the front rebound to be higher than the bump, that helps agility and transient response (S-curves, Les Combes)
- as mentioned, the rear ratios are wrong, if the damping ratios (front & rear) lie between 0.5 and 1, the correction factor is 0.25, if the ratios are higher than 1, the correction factor is higher as well, so it is not constant (not intuitive, I know)
- so at default the front bump ratio is 0.87, the rear displays as 0.81 - the correct rear bump ratio is then ca. 1.15, hence too much
- so increase rear rebound, decrease rear bump and increase rear rebound to bring it in line with the rear bump

ARBs
- since the actual value is not displayed, this limits our understanding and recommendations of this item
- suffice it to say, a one click adjustment on the front ARB has a higher effect on handling than one click at the rear on this car, this applies to GT3 cars in general
- since we decreased the front spring rate, we have to compensate with +1 ARB_FRONT to retain the absolute roll stiffness and its distribution between the front and rear axle
- if the car still understeers, then increase ARB_REAR

Tyre pressures
- the optimal pressure for GT3 tyres (even in v10 as far as I can tell) is 33 psi
- as anecdote, was driving a custom GTLM car on Spa yesterday for which optimal pressures are 35 psi, difference between 33 and 35 psi on this car was 0.7x seconds a lap
- the default cold 25 psi should rise to the desired 33 at 80 degrees, if front or rear tyres are below that through most of the lap, increase pressures accordingly

Height
- set ride height to lowest possible, to 0, you won't have issues with the minimal requirement
- benefits: a lower cg for faster transient response, a slightly higher CL (coefficient of life (freudian slip, lift)) from front splitter and diffuser
- the actual ride height is not the one displayed in the car status, look for it in the aero app, GH (ground height) in yellow for front splitter and diffuser
- the actual collider of the car model has a seperate height value from the cg, in the physics files

Aero
- at the bottom of the aero app, you'll find the sum of the lift & drag coefficients and the total downforce and drag values in kg
- the calculations of this app only work during driving and not during replays
- an increased AOA (angle of attack) of the front splitter has nearly no drag penalty, for maximum downforce adjust only the rear wing for the following point:
- look at %@front, have it between 46 and 49% for a balanced aerodynamic load on the front and rear, anything above 50% is inherently unstable, this value will fluctuate whilst driving, so make some screenshots to look at it more closely on the desktop

Camber & toe
- the default rear toe is way too positive, resulting in more understeer - I personally am a big proponent of toe values of 0, a seperate topic, so take these as you like
- set toe to or close enough to 0, better to have it positive than negative at the rear, +/- 0.02 radiants in the front are ok
- as mentioned above, the grip decreases with increased slip angle slightly sooner in the new v10 tyre model than with v7, so make the static camber angle a bit less negative as pictured below
- static camber, because the camber angle fluctuates during cornering - more negative camber leads to a higher slip angle (see suspension app, purple SA value for more details)
- in general, anything more negative than -3.4 degrees is too much for these GT3 tyres (v10, v7, v6)

Differential
- lower DIFF_COAST to 40% for more turn-in, if unstable under braking increase to 50%

Traction control
- the default setting when you load the car is not setting 1 on the traction control list
- TC is defined in the physics files as slip ratio limit, say 0.11 - hence if this ratio is reached, the TC will kick in - the higher the TC setting (CTRL+T), the higher the slip ratio limit, the less restricting it is
- increase TC, if you have understeer out of corners - a too high setting will result in oversteer of course
- all above points apply to ABS as well

That's it for now, have at it.
Gonna make some food now, tortelloni with broccoli and zucchini.
Click to expand...

I would understand as how to find the right balance between compression and rebound and the right frequency, I am using the lamborghini st, use a ratio 1-1 on front and rear 0.6-0.6 3.2hz -2.9hz

Andrea Mantovani, Apr 11, 2017

#165
Georg Siebert Simracer

Andrea Mantovani said: ↑

I would understand as how to find the right balance between compression and rebound and the right frequency, I am using the lamborghini st, use a ratio 1-1 on front and rear 0.6-0.6 3.2hz -2.9hz
Click to expand...

Try the following and check ride height and alignment after adjusting spring rate. This will yield you 3.2 Hz F and 3 Hz R as ride frequencies.
100 N/mm FSR (Front Spring Rate)
115 N/mm RSR

Since Front Bump can't go lower than 1.1 zeta on the Lambo ST, set up your dampers as 'upside down' - high bump, low rebound. Many race car teams do this successfully well. With
1.1 FBR (Front Bump Rate)
0.77 FRR (Front Rebound Rate)
1 RBR
0.73 RRR

or in the Dampers setup screen as
0 FB (Front Bump)
4 FR (Front Rebound)
8 RB
8 RR

This will give you good control through the corners and enough complience over bumps. If you get oversteer, correct with 1 click lower Rear ARB. Look at Fast Dampers for fine adjustment.

Georg Siebert, Apr 11, 2017

#166

chksix and baboon like this.
chksix Hardcore Simmer

I'm having troubles in the GT3 Merc at Zandvoort. The track is insanely bumpy so I have a hard time making the car track correctly. I'll try your upside down tip and see if it improves controllability.

chksix, Apr 12, 2017

#167

Eduardo AuKiss likes this.
Andrea Mantovani Rookie

Georg Siebert said: ↑

Try the following and check ride height and alignment after adjusting spring rate. This will yield you 3.2 Hz F and 3 Hz R as ride frequencies.
100 N/mm FSR (Front Spring Rate)
115 N/mm RSR

Since Front Bump can't go lower than 1.1 zeta on the Lambo ST, set up your dampers as 'upside down' - high bump, low rebound. Many race car teams do this successfully well. With
1.1 FBR (Front Bump Rate)
0.77 FRR (Front Rebound Rate)
1 RBR
0.73 RRR

or in the Dampers setup screen as
0 FB (Front Bump)
4 FR (Front Rebound)
8 RB
8 RR

This will give you good control through the corners and enough complience over bumps. If you get oversteer, correct with 1 click lower Rear ARB. Look at Fast Dampers for fine adjustment.
Click to expand...

thanks for the reply, I wanted to know how do you know the values of macchine..hz and compression and rebound relationship, for example, if you use a Ferrari SF15-T how do I know the right value? also use the motec

Andrea Mantovani, Apr 13, 2017

#168
Georg Siebert Simracer

Andrea Mantovani said: ↑

thanks for the reply, I wanted to know how do you know the values of macchine..hz and compression and rebound relationship, for example, if you use a Ferrari SF15-T how do I know the right value? also use the motec
Click to expand...

install directory\assetto corsa\system\cfg\assetto_corsa.ini -> set enable_dev_apps = 1 -> game -> right ui -> car engineer
Knowing the most suitable values comes from studying theory, empirical testing and experience.

Georg Siebert, Apr 14, 2017

#169

deni80s likes this.
Eduardo AuKiss Racer

great topic

Eduardo AuKiss, Apr 22, 2017

#170
Eduardo AuKiss Racer

really like the topic, but I want to know how to find the right frequency distribution between front & rear axle on GT3 cars and the damper ratios too. thank you anyway.

Eduardo AuKiss, Apr 23, 2017

#171
Kade Hardcore Simmer

Eduardo AuKiss said: ↑

really like the topic, but I want to know how to find the right frequency distribution between front & rear axle on GT3 cars and the damper ratios too. thank you anyway.
Click to expand...

The mechanical grip gain playing with frequencies is secondary to aero effects gained when springs are optimized for it instead. Driver comfort is not an issue in a simulator (or in racing anyway).

Kade, Apr 23, 2017

#172

Eduardo AuKiss likes this.
Georg Siebert Simracer

Eduardo AuKiss said: ↑

really like the topic, but I want to know how to find the right frequency distribution between front & rear axle on GT3 cars and the damper ratios too. thank you anyway.
Click to expand...

Set distribution as equal and go from there. You can try to have
RFF = RFR + 0.1 / + 0.2
(Ride Freuqency Front / Rear)
but keep the overall roll stiffness in mind and set a one click lower FARB (Front Anti Roll Bar) with increased RFF.
Downforce only enhances the mechanical grip, and the best aero setup can't compensate for poor mechanical grip.

For dampers, identify what type of damping setup the car has and adjust accordingly:
normal (rebound higher than bump)
or
'up-side-down' (technical term) dampers, (bump much higher than rebound - dampers act as dynamic springs) example in post #166 in this thread.
Default setups are all over the place on dampers, so don't be suprised.

Georg Siebert, Apr 23, 2017

#173

baboon, chksix and Eduardo AuKiss like this.
PhilS13 Alien

Georg Siebert said: ↑

the best aero setup can't compensate for poor mechanical grip.
Click to expand...

It does compensate and more. By quite a lot.

@Eduardo AuKiss go with what @Kade said and choose the springs that optimize splitter and diffuser heights.

PhilS13, Apr 23, 2017

#174

Eduardo AuKiss likes this.
Andy-R Alien

I had a go in the Audi GT? this evening and actually quite enjoyed it. More so than the AMG GT3 that I tried just before, i'm about 1sec a lap faster round Monza in the Audi than the Merc. I want to improve my time there in the Audi, is it possible to optimize splitter and diffuser heights using info from AC (dev) apps alone or do you need motec?

Andy-R, Apr 23, 2017

#175
PhilS13 Alien

andy-riches said: ↑

I had a go in the Audi GT? this evening and actually quite enjoyed it. More so than the AMG GT3 that I tried just before, i'm about 1sec a lap faster round Monza in the Audi than the Merc. I want to improve my time there in the Audi, is it possible to optimize splitter and diffuser heights using info from AC (dev) apps alone or do you need motec?
Click to expand...

@andy-riches in modern race cars? Impossible.

Motec doesn't help for that. I can save you the headache for the Audi...run it as low as you can. Just don't assume it's the same for other cars.

Otherwise everything needed to optimize aero heights is in there
https://www.assettocorsa.net/forum/index.php?threads/wings-app-for-dummies.43463/

PhilS13, Apr 24, 2017

#176

Andy-R likes this.
Andy-R Alien

PhilS13 said: ↑

@andy-riches in modern race cars? Impossible.

Motec doesn't help for that. I can save you the headache for the Audi...run it as low as you can. Just don't assume it's the same for other cars.

Otherwise everything needed to optimize aero heights is in there
https://www.assettocorsa.net/forum/index.php?threads/wings-app-for-dummies.43463/
Click to expand...

Thanks, I will download the app tonight. Sounds like the Audi was a good choice if all I need to do is slam it

Andy-R, Apr 24, 2017

#177
Georg Siebert Simracer

PhilS13 said: ↑

It does compensate and more. By quite a lot.

@Eduardo AuKiss go with what @Kade said and choose the springs that optimize splitter and diffuser heights.
Click to expand...

Nope, disagree.

@Eduardo AuKiss Choose ride frequency for mechanical grip and don't worry about splitter and diffuser heights - the change of CL (coefficient of lift) for 10mm to 20mm of compression or decompression during load is laughable. Rake angle doesn't change significantly either. You may set static height as low as possible for CG height for instance.

Last edited: Apr 24, 2017

Georg Siebert, Apr 24, 2017

#178

Eduardo AuKiss likes this.
Kade Hardcore Simmer

Georg Siebert said: ↑

Nope, disagree.

@Eduardo AuKiss Choose ride frequency for mechanical grip and don't worry about splitter and diffuser heights - the change of CL (coefficient of lift) for 10mm to 20mm of compression or decompression during load is laughable. Rake angle doesn't change significantly either. You may set static height as low as possible for CG height for instance.
Click to expand...

Actually you're kind of right. I haven't driven GT3 cars for a couple of months now and apparently the CL variation have changed recently. It depends on a car though and don't forget softer spring also gives mechanical grip, it's not only about front-to-rear frequency ratio that matters. Especially on heavily damped aero cars..

Kade, Apr 24, 2017

#179
benvolio Rookie

Edit

Last edited: Aug 5, 2017

benvolio, Aug 5, 2017

#180

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