Setup help: Lotus Evora GTC oversteers and crashes approaching downhill turns at Nordschleife

Ken Tegrum

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Jan 11, 2015
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Unfortunately when I ‘panic brake’, i.e. applying 50 to 75 of braking power suddenly, long before turning into a corner, the car will just spin out on corner entry.

I used a setup heavily sourced from Zandvoort.
Image of the setup used at Zandvoort in an Excel spreadsheet:

Nordschleife setup:


The oversteer is very common at downhill curves, especially at Kallenhard, and Ausfahrt Breidscheid.
I’ve included two video clips depicting the spinout at the corner, with the pedal inputs at the lower right hand corner.
https://gfycat.com/EnchantedSingleCarp
https://gfycat.com/somefavorableanemonecrab

The reason the recording is ‘laggy’ is because OBS wasn’t configured properly on my end.

I’ve also included two different excel file as well as the AC ini file from ‘My Documents’.
The xlsm file features a macro to duplicate the conditional formatting (color) from cell H7, to the cells specified in cell A54.
https://drive.google.com/open?id=1zAuIbtVrLOmEjHc-DniOF4ciyIq4ANtm
 

Kek700

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I have not got a clue as to what setup software you are using.
So i cannot say with any certainty if this is a correct statement.
The setup sheet suggests you have an large amount of toe out at the rear.
If this is the case you will have a lot of oversteer instability with the car, which
video seems to suggest. Although i can think of a number of other causes, but
there are far more knowledgeable people on this forum than me who, will i am
sure, give you advice.
Funnily i find the lotus to be a very stable car to drive..
 
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RasmusP

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I forgot which evora that one is but got it abs?
Even if it has abs, it sounds like locking rear tyres so if it's possible, move your brake bias to the front.
If it's not locking up rears, it might be:
- Toe out at the rear like Ernie said
- rear arb too soft
- not enough rear wing
- too soft/fast rear rebound damper setting
- too soft/fast front bump damper setting

Or just you being not good enough. Sounds harsh but I had the exact same problem with the lambo gt3 for weeks!
Then I didn't touch that car for half a year, only raced the gte pack in rfactor 2 and when I went back to ac, same setup same lambo, no ac update or anything and approached exactly the corners you mentioned (pflanzgarten jump being worst), it was all fine.
It's how you approach the brakes, turn in and throttle. Having a more stable weight shift process.
Can't explain it better, rf2 gte pack just somehow made me a better driver. Oh and I was 8 seconds quicker too :)
 
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Tardy Tony

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Working from memory, but I seem to recall the GTC is very sensitive to diff settings.
 

Kek700

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He seems to have, a highish diff coast and lowish diff power. So in this case,
it does seem to apply; but what do i know.:rolleyes:
 

RasmusP

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Just tried your setup, sat down and really tested the car, setup etc.
The problem is not related to the braking but to off-throttle balance! Download the "skidpad" mod track that's available here at RD and drive in circles. Your setup (default is the same behavior btw) looks like this:

It really reminds me of me driving the lambo earlier this year, which looked like this:

So there are 2 possibilities:
1. You learn how to drive this car, which from my experience with the Lambo means:
- At corners where the car becomes unstable -> keep the throttle at 10-20% while braking. When the rear starts to come around open up the steering and lift the brakes. The car will have slight throttle and will stabilize
- Turn in more smoothly and not too far. Turn in slower and let the car rotate on its own without actually steering it around

The problem is that my inputs in MoTec almost look identical to when I had my difficulties but I don't have them anymore. It's just this little push you need to get rid of. Try to turn in very slowly and only really steer when the car is stabilized again. Don't touch the brakes once you lifted them. Brake hard, slowly lift them, very very carefully and slowly turn in. As soon as the car starts to rotate open up the steering wheel a little, let the car settle and go gently on the throttle. When the car is stable turn in further and go around the corner.

When you watch the slomo part of my Lambo-Video you'll see that the rear is actually stable while I'm braking but the moment I lift the brake pedal the too high steering angle will just throw the car around. That's the crucial part to work on :)
Sadly you can't implement a video with a timestamp so here's the pure link to my latest Qualy-Lap in the Lambo. Jump to 7:00 to see the Pflanzgarten jump without me spinning. I really don't see much difference...
I brake, hold the brakes at a little percentage, turn in, lift the brakes and the tyres start to squeal. But then the car stays absolutely stable the moment I don't turn further, expect the slide and gently go back on throttle and make it without problems.
Maybe watch both videos side by side at x0.25 Speed to spot the differences and also watch your own replay and try to spot similarities :)
LinkToMyQualyLapAt7minutes


2. You change your setup until the car is very different from its natural behavior and it will probably be slower and also unbalanced on other occasions. I won't recommend this...
 
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Kek700

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He seems to have, a highish diff coast and lowish diff power. So in this case,
it does seem to apply; but what do i know.:rolleyes:
I meant, does not seem to apply in this case.

I would like to know where the instability is derived from!
 

RasmusP

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I meant, does not seem to apply in this case.

I would like to know where the instability is derived from!
It's just the car! It's stable under heavy braking and very stable and slightly understeery during normal acceleration. It's kinda "short and stiff" though so once you destabilize it, it'll come around.
It's very difficult to catch when you spin the rear tyres due too much throttle and it's also twitchy when you load the fronts just slightly to give them grip (trailbraking).
Drive the Audi R8 GT3 or Lambo GT3 and you'll experience similar behavior. But the Lotus is shorter and not that planted after all and therefore the limit is a lot smaller and snappier. If you change the setup to get rid of this, you'll have a car that won't turn under braking and won't steer at all when you're on throttle.

So best way is to turn less than you want to at turn in while you're still slightly on the brakes and once the car rotated barely enough to make the corner to go smoothly back on the throttle to gently move the weight off the fronts without triggering understeer.
Had a touch time with the Lambo!
 
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Kek700

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i had a vx220 with the engine above the gearbox, on the limit it had a strange
handling trait, like a rear roll oversteer. I had always assumed it
was due to the phoney mid engine layout. Engine above gearbox, the engine
Mounted longitudinal, giving the car a high rear centre of gravity.

I am “assuming” the evora has the same configuration but with a heavier engine.

Just a guess really?
 

RasmusP

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i had a vx220 with the engine above the gearbox, on the limit it had a strange
handling trait, like a rear roll oversteer. I had always assumed it
was due to the phoney mid engine layout. Engine above gearbox, the engine
Mounted longitudinal, giving the car a high rear centre of gravity.

I am “assuming” the evora has the same configuration but with a heavier engine.

Just a guess really?
That makes a lot of sense! The vx220 seems to be a collaboration with Lotus on the Elise. The Evora is just a longer Elise so maybe the engine+gearbox layout is similar!
And yep, feels like "rear roll oversteer" indeed!
 

Tardy Tony

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Curious, I could not get the car to behave badly with the default setup. It was a bit oversteery throttle off with provocation, but 80% coast fixed that.
 
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Mr Deap

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Camber value should have closer value front & back based on the ride frequency.

You can also increase the wheel rate at the rear for better match up of the ride frequency to be more predictable. Good example, as matching up the ride frequency... Under braking the car pivot, if the front weight 10kg less, the front suspension need to be tuned to have less wheel rate to follow the body movement while braking.

Demo with toy car how the suspension arm move under compression, it's like how skateboard do. It lean & turn for ya. You adjust the alignment based on that logic, not because you need to be different.

Alignment & what the suspension geometry does is important to understand & get it right. The larger the suspension move up & down... The less aggressive toe value is needed & the more negative camber is needed. It's possible to have aggressive toe value, low camber value(example -1 degree), because combined with strong ARB value. But outside that, it's a general rule based on the behavior of a suspension arm.

Differential is more about sweet spot value
Too much value, it slide, too little it also slide for when on/off setting. It's about matching the speed the wheel do when cornering.
 
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PhilS13

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Akdjkld,

dkjris drje ikfyopm jfhve. Idnj sjjskrr kaakue ajnlein.

fjioea!

Dionsskirpemd
 

RasmusP

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Akdjkld,

dkjris drje ikfyopm jfhve. Idnj sjjskrr kaakue ajnlein.

fjioea!

Dionsskirpemd
Hehe, if you can be bothered I'd like to hear your opinion about this car. Do you think the default setup is "bad" or do you think it's okay/good and one should rather learn how to drive with it?
 

Mr Deap

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Every car, except the road one need to be learned with the default setup. @PhilS13 is right on that, because that's how you have you get used to the learning curve much faster(hold brake pressure & turn at the same time).

You often hear, "You release the brake as you turn in"

In AC... "You turn in as you release the brake"

I did give a name to this method, but some get offended. :D
 

PhilS13

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Hehe, if you can be bothered I'd like to hear your opinion about this car. Do you think the default setup is "bad" or do you think it's okay/good and one should rather learn how to drive with it?
Don't know if they are fast but both the defaut and the setups here in the first post are good to drive. I am incapable of spinning like in the gifs on both sets.

When the rear starts to go, on any car, going zero on both pedals and trying to bring it back with steering only is never going to work very well. Give it 10-20 % throttle and the car goes back in line just fine.

You often hear, "You release the brake as you turn in"

In AC... "You turn in as you release the brake"
So
5 = 5
5 = 5

I see you are targeting to start making sense in 2019. Good for you. :thumbsup:

For the newcomers, we have this very cool thing going on for years in simracing. It's called Mr Deap. From time to time (it seems it's cyclic), he will make these "advice" posts that contain a lot of vehicle dynamics words but arranged in a way that even the best experts in the world couldn't figure out what exactly it means. Some think he only has issues arranging the words but most likely he simply has no clue what he is talking about. You are probably wondering : "then why don't you prove him wrong and explain instead of mocking him? Maybe he'll stop." Good point! But we already tried. That was many years ago.
 

Mr Deap

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Kk I'll explain the difference between the statement.

"You release the brake as you turn in"
You release the brake pressure first, after you turn in

"You turn in as you release the brake"
You turn in, after you release the brake pressure

It's not 5:5... It's 2 completely different method. It's like when you brake mid corner. One will require you to release steering while adding brake pressure. One will require you brake & add steering.

I suppose the topic creator made the setup that way, due to the odd understeer & being misleaded from reputable source. Sim racing is quite fascinating in many way.
 

Kek700

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@PhilS13 , thats interesting because i too find the evora easy to drive, but having spent many years with stiff rear, front wheel drive cars, that would spin so fast when lifting with the slightest
hint of steering angle. I have got into a habit ( probably pointless ) of always applying
some modulated throttle when braking and turning ( unless i require 100% braking ).
I am sure there is a lot to criticise with this process. Because it is mostly subconscious,
it may have made driving some cars easier. ( who knows ). or of course i could
have spent my life pointlessly modulating a throttle. All that pollution.:rolleyes:
 
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RasmusP

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@PhilS13 , thats interesting because i too find the evora easy to drive, but having spent many years with stiff rear, front wheel drive cars, that would spin so fast when lifting with the slightest
hint of steering angle. I have got into a habit ( probably pointless ) of always applying
some modulated throttle when braking and turning ( unless i require 100% braking ).
I am sure there is a lot to criticise with this process. Because it is mostly subconscious,
it may have made driving some cars easier. ( who knows ). or of course i could
have spent my life pointlessly modulating a throttle. All that pollution.:rolleyes:
Imo that's all making sense! I on the other hand never really drove with any car that has lift off oversteer. At least not to an amount that spins you right round.
Mostly driven the tatuus, the Mazda mx-5 cup Audi TT Cup or the gt4s. I remember from my first online races though that the abarth 500 had a similar behavior going into pouhon/double gauche at spa. It won't spin but it would drift, lose speed and then massively understeer. Playing with the throttle to keep it stable helped a lot. Never needed it again though.
Then I drove a lot with the mclaren 650s gt3 at the nords with a very special setup. Was pretty fast but it had not such behavior too with it.
The gte pack in rf2 doesn't have it either.

Felt like a big noob spinning the lambo that often...
Thanks for your input guys :)
 

PhilS13

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Sep 14, 2010
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@PhilS13 , thats interesting because i too find the evora easy to drive, but having spent many years with stiff rear, front wheel drive cars, that would spin so fast when lifting with the slightest
hint of steering angle. I have got into a habit ( probably pointless ) of always applying
some modulated throttle when braking and turning ( unless i require 100% braking ).
I am sure there is a lot to criticise with this process. Because it is mostly subconscious,
it may have made driving some cars easier. ( who knows ). or of course i could
have spent my life pointlessly modulating a throttle. All that pollution.:rolleyes:
I don't apply throttle under braking. I remember this being discussed and me checking if I was doing this, even subconsciously, I could have...but turns out I don't. So it's not a necessary thing. It is very helpful though to be aware you can settle the rear down mid corner with a bit of throttle.
 
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