Packers !!!!

[Kek700]

can some knowledgeable person please explain.

I would like to use them but I cannot see how to utilize their use and cannot find anything on the Internet about it.

They have a travel range and somehow combine with suspension springs stiffness and travel
adjustment so is it easily possible to make a meaningful adjustment.

Also Is it possible to give a pictorial representation of them to help understand their use or
are they just a theoretical part of the physics calculation.

 

[mclarenf1papa]

“Packers” in AC are just bumpstops (rubber stops put in the suspension to increase springrate after a certain deflection).

 

[Kek700]

thankyou you for clearing that up for me, I started to create some sort
of complex mechanism in my head.

 

[Tbear]

@mclarenf1papa has it exactly correct.
Just be careful not to confuse "bump stop" with the bump and rebound functions of shock absorbers (dampers).

 

[Kek700]

Now there is another subject that I also find mysterious.

 

[Tbear]

Now there is another subject that I also find mysterious.

Ezy Pzy! The piston in a shock absorber goes in ... and out, or up and down when mounted in a car. Hit a BUMP and the piston compresses in one direction, hit a dip in the road and the piston compresses in the other direction. Bump and Rebound. The damper does this to control the up and down motion of the springs in the car.

Now I could frame that description talking about spring oscillations but it would only confuse the issue.

 

[mclarenf1papa]

Ezy Pzy! The piston in a shock absorber goes in ... and out, or up and down when mounted in a car. Hit a BUMP and the piston compresses in one direction, hit a dip in the road and the piston compresses in the other direction. Bump and Rebound. The damper does this to control the up and down motion of the springs in the car.

Now I could frame that description talking about spring oscillations but it would only confuse the issue.

Or a much simpler way of thinking about it, the damper produces a resistant force in the opposite direction of the damper/spring's velocity/travel. In other words, it makes the suspension harder to compress/extend.

When the suspension is being compressed, the damper resists that compression with its bump rate (which is dependent on the speed of the compression); when it's being extended, the damper resists the extension with its rebound rate (dependent on speed of extension).

 

[Kek700]

I really appreciate your explanations,

Rubber bump stops i have come across, packers is a new one on me, thought is was a spring
which could be compressed at the end of the main springs stroke. “ obviously got that wrong “.

Bound and rebound both slow and fast.......

Its “implementing” them in a measurable way to extract more performance from the car.
I can and do boringly battle my way around the circuit in an attempt to find the fastest setup,
which in the end almost always comes down to bump,rebound,fast bump and rebound.
But it is always a “complete” guessing game,with a very “little” bit of educated guessing thrown in.
I dont do a few laps and then make an ....“ah! Statement” ..... I need two clicks of bound on
the front to control entry rotation or some such thingy.
I would also like to understand it from an assetto corsa sim situation, rather that plugging away
not knowing if the adjustment even works as it should in assetto corsa or am i refining my driving
and better controlling high speed entry with my driving and not the damper setting i have
laboriously plugged away setting. ( perhaps i want too much )

it is probably a personal failing, and i just do not have the feel.

This all started with trying to get Eau rouge at Spa turn in flat out, which i just cannot do in
my Nissan Gtr gt3
It understeers just at the entry turn in to Eau rouge, meaning i have to momentary lift and turn.
I had hoped the packers would take up the dip at Eau rouge with some added fast bump
and rebound control. Then this would then allow me to take Eau rouge flat out,hopefully
without effecting the rest of the circuit.
( which i have spent many laps guessing anyway )

Apart from the packer question thats all i meant about bound and rebound.

 

[RasmusP]

I had hoped the packers would take up the dip at Eau rouge with some added fast bump
and rebound control.

Problem here is that a stiffer front will respond quicker to your inputs but at the same time will have less mechanical grip.
So you would probably need to go as soft as you can without losing control over the wonky car but have an eye on the aero app.
If the aero stalls, you would need to get the packers/bump stops to restrict the front of going too low.
If you don't have a packer rate, it's really just a bump stop!

Also the dampers are very linear. Like a constant resistance. It does the job but it doesn't have the real life dynamic and therefore also not the major influence real life dampers would have.

In ACC however the aero settings are really basic and you don't have to change the whole gt3 car every time.
What you do though, as Aris described in his blog posts, is to play with the rake and the ride heights in general!
Dampers are a lot more dynamic now so have more influence.
Also the packers are real packers now.
It's no longer about the whole setup. It's mainly about height+rake and then stabilizing (or destabilizing) the aero balance with dampers and packers.

One advice I would give you for AC:
Open the "car engineer" app and you will see the spring rates and the damper ratios.
Set the springs like you want to. They give the car the general stiffness or softness.
Then try to put all ratios to 1.0! It's not the fastest and might not feel the best but in theory your suspension is perfectly damped. Being as soft as possible while maintaining the perfect amount of de-bouncing.

You will see that this isn't always possible! The rsr f3 mod for example has such a low ride height that you need incredibly stiff springs! If you go with "1.0" you have an uncontrollable way too stiff plank!
So you massively underdamp that car and you can really feel around tracks like Zandvoort that it's not great.
So I once tried to even out the dampers and springs. Had to raise ride height too of course.
Car was way better to drive! Sadly it was a whole second slower...

To sum it up: try to set dampers to 1.0 and go from there. Also check what's the default so you know in what direction you should go from there

 

[Pawel Ziolkowski]

But it is always a “complete” guessing game,with a very “little” bit of educated guessing thrown in.
I dont do a few laps and then make an ....“ah! Statement” ..... I need two clicks of bound on
the front to control entry rotation or some such thingy.

Unless you have telemetry and practical data from previous races it can be a guess game IRL too. That's why consistency is so important, you want to do a change and be consistent enough to tell if it was good, bad or had no impact at all.

Let's take an example: you are at SPA, turn 11 (left-hander before pouhon) in your GT2/3 car, you cut the kerb, car washes wide on exit.
Now if you study the sequence frame by frame it turns out that when car was coming down from the kerb, both front wheels first compressed hard and then bounced up together. As the car went up front splitter lost a lot of downforce and car stopped rotating washing wide.
Solution? Crank fast rebound damping on front wheels up, so the bounce up is reduced saving the downforce.
Now as a side note, in theory you could increase front fast bump too, to reduce the amount of energy stored in compression, but making front suspension too stiff on landing will make tyres store the energy instead so the car will still bounce and have less grip.

Now are you able to run that T11 kerb to the same depth and speed up to 20-30cm and 3-5km/h every lap to notice the improvement? The more you are off, the more murky the water becomes in the setup pool.

It understeers just at the entry turn in to Eau rouge, meaning i have to momentary lift and turn.
I had hoped the packers would take up the dip at Eau rouge with some added fast bump
and rebound control. Then this would then allow me to take Eau rouge flat out,hopefully
without effecting the rest of the circuit.

Eau rouge is as much about correct line as it is about setup. Remember that donington setup you gave me? It does not use packers at all, but if you adjust your line so that car is far to the left and then turn right very early you can go flat out with it.

Now setting packers can help. Use drop the car as much as possible and use front left packer to reduce scrapping, and more importantly you can use rear left packer to move grip balance forward in compression so the car can turn more initially and being ok with turning less in the following climb where front looses downforce.

 

[RasmusP]

Now setting packers can help. Use drop the car as much as possible and use front left packer to reduce scrapping, and more importantly you can use rear left packer to move grip balance forward in compression so the car can turn more initially and being ok with turning less in the following climb where front looses downforce.

That was a really fresh thought for me to chew on! Didn't think about it at all. I know you can do similar for going on the throttle with damper settings but I didn't think about "real" compression where you could use even the packers.
Thanks for that!

 

[Kek700]

Again, thank you for your help,
i have tried critically dampening the car as you have described,
getting the value to near 1 and over. And yes it does help with the amount of time i am off throttle
at Eau rouge, but i still have to lift momentarily.
Even though I run my Nissan very stiff at the front and very low come to think of it.
I need a bit of give in the dampers to reduce its understeering nature for the rest of the circuit or at least slow it’s response down to give the front end time to naturally respond. Otherwise it just seems to plough on; yes i know it is not ideal but this is where i am at with the car at this moment in time, alas, with my limited abilities.
Running it soft seems to make a nice car to drive, but i loose time per lap, even though i can gain
on some corners. I know this sounds like a contradiction ( sorry ) but on some “odd”circuits i set
the car up too run soft for improved lap times.
It may be an aero problem, but i do run a stiff front, and I don’t think that it is a problem. I have tried
timing my turn in just prior to the corner and actually once managed flat out, “ if that was a legal corner “ not sure.?
But trying to judge a turn in at 250km/h to within 1 metre every lap is well beyond my abilities.

 

[Kek700]

Sorry about the post being out of sequence, always trying to do more than one thing at once.

 

[Kek700]

You are absolutely correct about T11, most of the time it pays me not to ride the curb, then sometimes
when i do ride it i gain time then next lap i loose a lot of time. So the corner get ignored in the scheme
of the whole circuit.
I have not tried your “packer” suggestions yet, i was trying to understand their function a bit more
before testing.

 

[Kek700]

Rasmus, were lucky to have Pawel helping out, he really knows his stuff.
With his much appreciated help i have knocked 0.5 second from my Donington GP lap.
A circuit i do not particularly like.

 

[RasmusP]

I'd say it might be time to go a completely different route and make the front really soft, adjust ride height to be just the minimum you need to save the setup and then raise the front dampers until it's "drivable" again.
If you scrape or the aero stalls (sadly you basically have to record a video to be able to watch the values): Lower the travel range until it's okay.

Complete opposite of your current approach but maybe it can be better?
Don't really have the time atm to run the car to test myself

 

[Tbear]

If you scrape ...

I've not experienced a car scraping the track in AC.

Can you see/hear/feel the car scraping?

Can you suggest a car/track combo where I might?

 

[Pawel Ziolkowski]

I've not experienced a car scraping the track in AC.
Can you see/hear/feel the car scraping?
Can you suggest a car/track combo where I might?

Take Nissan GTR gt3 to any non flat track and lower it down to minimum (55mm both front and rear) It's a scrape city from there. (for example mugello is not flat enough)

You can reduce wind, tyre, engine and transmission sound in the app, but i think scrapping is disabled for replays, so look for it live when driving.

 

[Kek700]

I'd say it might be time to go a completely different route and make the front really soft, adjust ride height to be just the minimum you need to save the setup and then raise the front dampers until it's "drivable" again.
If you scrape or the aero stalls (sadly you basically have to record a video to be able to watch the values): Lower the travel range until it's okay.

Complete opposite of your current approach but maybe it can be better?
Don't really have the time atm to run the car to test myself

I understand exactly what you mean.

This started as a niggle about Eau rouge because i noticed people running it flat out
6 weeks later I’m in the same place as i started with Eau rouge.

Yes i know i could run a Mclaren 650 gt3 but that would be too easy would it not.!!

Although i have gleaned a lot of information on route.

 

[Pawel Ziolkowski]

@Kek700 One thing of note in regards to going really soft and Eau rouge. It may not work, because during the climb part of it car is getting lighter, so soft suspension will rise it really high completely killing downforce, thus drowning any damper adjustment in terminal understeer of front splitter stall.

edit:

Rasmus, were lucky to have Pawel helping out, he really knows his stuff.

Not really, while answering the questions on this forum im learning a lot too haha. People like mclarenf1papa are much, much more knowledgeable on racing. Im just playing a video game and sometimes i get it wrong too .