General Tuning Guide (Updated 1.09)

Discussion in 'GT6 Tuning' started by DolHaus, Jan 16, 2014.

  1. DolHaus

    DolHaus

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    Thats perfect, thank you :tup:

    Your descriptions are just what I'm looking for in terms of feedback which will make the rest of the process much easier.

    One of the most important things to remember is that you should only adjust one setting at a time, this way you can pinpoint exactly what settings are responsible for the resulting changes. If we were to change the spring rates, tweak the dampers, arb's, alignment and LSD all in one go and then hit the track we would probably find some improvement in places and losses elsewhere but we'd have no idea why and therefore no way of efficiently continuing development.

    To me this sounds like issues typical of the default full custom LSD settings, I've not found many cars that work well with the default numbers so I have no idea why they chose them.

    This charming video from the1930's should explain the basic principals of a differential and why we need one in a car. As far as GT6 tuning goes this is all the basic theory you need to know, as far as I can work out the behaviour doesn't resemble any kind of real world technology but they are very easy to manipulate.



    The fully customisable LSD is broken up into 3 settings with values between 5-60 and each of these relates to a specific phase of driving:


    Initial - Coasting/neutral

    Acceleration
    - On throttle

    Deceleration - On brakes


    We can describe a differential as being open or locked, an open differential allows the connected drive wheels to rotate at completely different speeds and a locked differential forces both wheels to spin at the same speed. In the tuning menu this is represented as 5 being as close to open as possible and 60 being as close to locked as possible.
    I will quote my original LSD post to save me writing it all out again but we will be using these principals to make our first changes.
    So the main problem with the default custom LSD settings is that the Accel is way too high which causes the outside wheel to slip while accelerating out of a corner, this is of course a problem for you as the driver because you can't get on the throttle fully until the car is pointing more or less in a straight line which costs us speed and time. By lowering this value we are basically allowing ourselves to get on the throttle harder and earlier when coming out of the corner which pays off big time on the track.


    So our current LSD settings are:

    Initial Torque: R= 10
    Acceleration Sensitivity: R= 40
    Braking Sensitivity: R= 20

    My first modification would be to half the accel so set it as below and take the car for a drive.

    Initial Torque: R= 10
    Acceleration Sensitivity: R= 20
    Braking Sensitivity: R= 20

    I want you to concentrate on how the car feels accelerating out of the corners and to keep an eye on the tyre temperature monitors. Most likely the car will still be oversteering a bit coming out of corners, you will notice that when it happens the outside wheel will light up first. The outside wheel lighting up tells us that we need to further lower our Accel to improve performance so half the accel once again

    Initial Torque: R= 10
    Acceleration Sensitivity: R= 10
    Braking Sensitivity: R= 20

    Test drive the car again with the new settings and continue to concentrate on the accelerion coming out of corners. If the car has stopped oversteering and is now giving smooth drive out of the corners then we're getting closer to our objective and lap time should be improving. Keep an eye on the tyre temperatures coming out of slow tight corners to make sure that the inside wheel isn't lighting up as this is a sign that the accel is too open and you are wasting drive and losing speed. If it is spinning the inside wheel then raise the Accel by one until it stops, it can be useful at this stage to keep increasing the accel until the outside wheel starts to light up to find the effective range of that setting for future reference.



    We can now move onto this part -


    This relates to the Initial setting in the LSD, by reducing the Initial value the car is more free to rotate and change direction. The down side of reducing the Initial is that the car can become unstable so we again need to find the balance point. Try reducing the Initial a bit and then give it a quick test concentrating on how the car behaves when coasting and how it responds when transitioning between braking/accelerating/neutral. If rotation and response seem to improve then keep reducing the number, if the car starts to get fidgety or misbehaving then increase the number until you start feeling understeer, by doing this you have again found your effective range.

    You didn't mention anything about the brakes but the process is the same if you want to play with this setting as well, by reducing the number you will be able to rotate the car more under braking but this can make the car unstable if set too low.

    As a general course of action I never set the Accel or Decel lower than the Initial value because this can cause some very strange behaviour from the LSD particularly in faster, more powerful cars. This said I've driven some cars tuned by others that didn't follow this rule and were fine so I'll let you draw your own conclusions, never rule anything out without trying first.

    Let me know what settings you end up with and give me an update on how the car drives and where you think it is performing well/struggling :tup:
     
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  2. speedy turtle

    speedy turtle

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    Thank you DolHaus. Now I have plenty of concepts to test.

    Very interesting video, It's simple but very well explained.

    On other threads and guides I've read it is useful to use 2 or 3 harder tyre compound to identify the lighting up of the tyre. Do you think it'd be useful on the Miata, or maybe we can trust on the visual data?

    I didn't mention anything about the braking process because it seemed to be ok, anyway I'll test it in the same manner to verify possible improves.


    ST70
     
  3. DolHaus

    DolHaus

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    Changing tyres is a bad idea because a tune is built purely around the tyres, every modification we make is to make those particular tyres work more effectively. It'd be like learning to run in sports shoes and then wearing mountain boots for the race :lol:


    We will get onto identifying problems with the suspension soon enough but first we need to make the car consistent and drivable, we must take care of the big, obvious problems before trying to refine the rest of it.
     
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  4. speedy turtle

    speedy turtle

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    Yes, a little uncomfortable running with boots :lol:

    I've been testing the LSD configuration from the standard Initial/Accel./Decel. = 10/40/20, lowering first the Accel. then the Initial, making a test after any individual change, through the following steps:

    20/20/20 - 15/15/20 (cause you recomend never use a Accel. or Decel. lower tan Initial) - (10/15/20) - (7/12/20) - (7/10/20) - (7/7/20) - (5/7/20)

    Using 20/20/20 or 15/15/20 I've notice a light reduction on the "going to orange" outside front tyre. I'd say the tyre was not blue nor orange. It stayed halfway...

    From this configuration and lowering up to 5/7/20, I didn't feel any improvement, I don't know if we are on the limits of LSD at this point of tune and need to continue with suspenssion, or it was a por driver that do not know how to obtain more sensations :guilty:

    The overall feelings are a little bit more confortable, although the lap time only improve 2 cents... Maybe I'd have to drive more time to obtain a very clean lap, but I think I've understood the LSD Accel. operation.


    ST70
     
    Last edited: Aug 28, 2016
  5. DolHaus

    DolHaus

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    The LSD is only acting on the driven wheels so it will have very little effect on the front tyres in this case (rear wheel drive), it will have a slight effect on how willing the car is to turn in and how well it can hold its line but it won't truly effect how much grip the front end has. To affect the grip and balance of the car we need to optimise the suspension rather than the drive line, our basic aim with LSD tuning is to allow us to put the power down effectively and remove rotational restrictions.

    My personal aim with LSD tuning is as follows:

    Initial - as low as possible without making the car feel twitchy or unstable
    Accel - between the point where the inside wheel and outside wheel light up
    Decel - as low as possible without the car becoming unstable or moving around during hard braking


    5/7/20 sounds more or less where I'd likely end up with this type of car. Personally I would probably lower the decel a little bit as I suspect it will be restrictive during racing as you often need to be able to rotate the car while on the brakes, it will also help when you get the corner a little wrong and out brake yourself as you will maintain more control rather than being stuck going in a straight line until you come off the brakes.

    We will return to the LSD tuning at many stages throughout the process as we make other changes and encounter new problems, its never a good idea to just set something and then leave it as it could be responsible for a multitude of problems that you could waste hours trying to solve by using other means. As long as you remember what you changed then you can always put it back if it doesn't work so don't be afraid to try.
     
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  6. speedy turtle

    speedy turtle

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    I tested the LSD numbers like you say, and yes I feel good with it, indeed, I lowered all of them (5/5/5) and there is no substantial differences, the rear is under control. Only the same front outside orange tyre, but we've already talked about it.

    One question about LSD accel.: If I didn’t misunderstand the concept or the use of it, we have that the higher the value, the better the acceleration. Since we start the tuning process, I’ve felt the car very lazy to react when push the throttle… Don’t we must increase the LSD accel. a few ticks? Or maybe is it caused by a poor powered engine?

    Thank you,

    ST70
     
  7. DolHaus

    DolHaus

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    If the Accel number is higher then you will get more positive drive out of the corners but the downside is that you have to wait longer to get back on the throttle coming out of the corner. Like most other tuning elements it is all about compromise, you want to be putting the power down as efficiently as possible (higher numbers) but you want to be able to get on the power at the earliest stage possible (lower numbers). In my experience the benefits are stacked more towards the open LSD, the additional drive you get from a tighter diff set up just doesn't balance in terms of lap time.

    The MX5 is notoriously weak in the engine department so you might benefit from chucking a few power parts on there to help illustrate the concepts better as I suspect you're not putting down enough power to highlight the problems effectively. Maybe bring it up to around 200-250 bhp (aim for 400pp)?
     
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  8. speedy turtle

    speedy turtle

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    Ok, thank you...

    Your last line was going to be my next question. I don't know if we've finished with LSD on this point of tuning... I was going to ask you if we're going to go to suspension or must add some power parts first?


    Another question out of context. Those “aromatic spices” like says Mater, at least on the spanish version of “Cars”; when can we set them up? racing brakes, clutch & flywheel, driveshaft,… anyway, those things that don’t add PP but they are there… I don’t mention the gearbox because I think it is very important and we won’t take a long time to set it up...
     
  9. speedy turtle

    speedy turtle

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    Talking about gearbox. How can we know the correct gearbox configuration? I mean, I know how to adapt it to a faster track or slower track using the last gear, it’s easy… the problem starts when I like to learn how to set the gears.

    I've read Mr. Praiano advice and Mr. Hamilton guide, they more or less say the same: last gear about 100%, 2nd gear about 20%, intermediate gears trying to divide de gap, and 1st gear in a similar gap...

    When you select each gear you have an effective range to choice, and you have to set the gears so that all the gaps between them would be similar or maybe a little narrower as you move to the largest gears… that’s easy again, but:

    Imagine a 5 gear gearbox that admits the following deal, i.e. 10%, 15%, 20%, 25%, 30% of the slide, or 40%, 45%, 50%, 55%, 60%, or 80%, 85%, 90% 95%, 100%. What is the right way? I don’t know if I’m explainig myself… In any case, after one of these distributions we’re going to use the final gear to adapt the speed to the track, and to extend or compress the gap between gears…
     
  10. DolHaus

    DolHaus

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    Ahh whoops, forgot about those :lol: Clutch, flywheel and driveshaft should always be fitted if allowed as they are worth maybe a 10th of a second each per lap, I personally prefer the twin plate clutch instead of the triple but 90% of the time it makes no difference as long as its upgraded. In the description it says that the triple plate can cause some RPM loss when going up hill, I have noticed this on some low powered cars so I always go for the twin as a result. Check them both and go with which ever you think feels best, during FITT testing there has never been a noticeable difference between either.
    Racing brakes aren't always an upgrade, sometimes they just cause the ABS to kick in earlier which reduces overall braking force so again it is a case of testing one against the other and picking which ever you think gives better performance. Never assume that something is a true upgrade just because its an option, always test it and make sure before committing to it :tup:
    The other questionable mod would be the rigidity upgrade from the main menu, in my experience this one adds a huge amount of understeer which can be a good thing in some situations but most of the time its really bad for performance and cannot be undone.
    As a general rule you want to begin tuning with the car fully built, not a great deal of point in slowly building it up as you'll just end up changing the same settings over and over. In this case we're just trying to keep it as simple as possible and not bothering with stuff that is otherwise just trial and error.

    Throw a few power mods on the car just for the sake of education. I'm trying to intentionally run into the more common problems that you will encounter so we can go through the process of correcting them together, low powered cars tend to have less problems with the LSD as the main job of this component is to do with power management. Once you've got the parts fitted then take the car out for a spin and check for issues, low speed hairpin exits will show up Accel problems and heavy braking zones will be where you'll find Decel related issues.

    We are never truly finished with a setting as unfortunately there is no such thing as a perfect setting, instead we just need the best compromise for our situation. The best we can do is knowing which parts are associated with certain behaviours and using this knowledge to find a solution logically.

    Transmissions are far from my speciality unfortunately, @Otaliema is your man for that one and his very in depth guide can be found here

    I would usually set 1st to 40% and 5th to 100% and then balance the rest more or less visually. I would aim to make 1st and 2nd fairly long (more to the left on the slider) in order to give more manageable power delivery at lower speeds and then shorten (more to the right) the higher gears to make sure the engine doesn't struggle
     
    Last edited: Aug 31, 2016
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  11. speedy turtle

    speedy turtle

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    Hello DolHaus:

    Thank you for the link to Otaliema's thread... Ufff, it 's very deep, I need some time to digest it :lol:


    Logically, when we talk about tuning, we'd first think into reach the PP limit adding some power parts, reducing weight, and using power limiter to fine PP adjust...

    I'm sorry, maybe I misunderstood the meaning of tuning process. When we start from scratch, I didn't think I had to assume that we start from a given powered car, I thought we started from "zero.zero", no power parts, no weight reduction, configurable but standard suspension, fully customizable but standard gearbox and transmission... and then, step by step go adding all the necessary components to tune a competitive car.

    Ok, I learned it.


    Step 2:

    I added Engine: phase 3, and Exhaust: sport, then:

    Perform.: 417 PP
    Power: 206 HP
    Torque: 23'95 Kgfm
    Weight/Power: 5'0 Kg/HP

    I tested the car with LSD 5/5/5, and found the same problems on front axis. But the rear wheels didn't show any problem with oversteer.

    Would you like me to add more power parts to reach 450PP, or can we continue?

    ST70
     
  12. coryclifford

    coryclifford

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    The "front axis" is your driving. Try slowing down sooner, more gently and not turning the wheel too much.
     
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  13. DolHaus

    DolHaus

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    With the LSD at 5/5/5 you won't get any oversteer unless the car is inherently unstable, the noticeable effect would be the inside wheel spinning under hard acceleration while turning and a tendancy for the rear end to become unstable if you attempt to change direction during severe braking.

    By zeroing the tune we are just taking it back to stock suspension and removing default settings that have a known negative effect, unfortunately I assumed the MX5 would have sufficient power to give the rear wheels trouble so that's why I didn't ask you to modify them. In any other tuning situation you want to start with all your power and weight upgrades fitted because they will have an effect on the way that things function, a 600bhp car will need a different LSD set up to a 150bhp car and a 1500kg car will need a different suspension set up to a 900kg version. A car running a fixed power and weight will need a different tune to perform at its limit if you change tyre type because again the key parameters have changed.
     
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  14. speedy turtle

    speedy turtle

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    I read the section in your guide where talk about the gap between Initial and Accel./Decel. and the smooth or violent that car reactions can be if the gap is smaller or bigger respectively.

    I noticed differences when change from 7/15/9 to 5/15/5. In the second one the car is easier to loose when push the throttle, but it can be controled yet. I tested more gap but the car started to slide and lost time per lap, though being careful with the steering wheel. You can correct the path, but the track width has its limitations.

    I would like to continue learning. Reading lots of guides and articles is a way, trial and error is an essential part, but it's important to know what you are doing to know if you are in the right way. I've learned this last week much more than the last whole year. Could you continue teaching me, please?

    Thank you very much
     
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  15. DolHaus

    DolHaus

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    Certainly, more than happy to continue :tup:

    If you are happy with LSD settings then we can move on to the suspension, our first task will be to first establish the balance between response and grip by manipulating the spring rates and ride height. The overall stiffness or softness of the springs is what will define how much grip can be generated by the tyres and how fast or slow the car will react to driver inputs (steering/accelerating/braking).

    The first thing we need to keep in mind is that everything we do with the suspension is directly related to the tyres. The tyres are arguably the most important part of the car and everything we do is to make them work at maximum efficiency. We have to accept that our tyres have limits and that we need to work within these limits to get the most out of them. I can go deeper into tyre theory if you'd like but will skip it for the time being.

    Soft springs will generate more grip as they help keep the tyres in contact with the road more effectively, the soft suspension is very compliant and reacts quickly to uneven surfaces so they chance of the tyre leaving the road is reduced. They are also very good a distributing and absorbing force so the chance of overloading the tyre is also reduced at low to medium speeds. The downside is that because the suspension is so soft and compliant it can become unstable because the weight transfer is hard to control and the car responds relatively slowly to driver input, this makes sudden changes of direction (ie. a fast chicane) difficult and increase the chance of losing control. The basic reason for the slow reaction is that energy transfers faster through a solid object than a flexible one, the faster the energy transfer the more direct the control.

    Stiff springs will generate less grip at low-medium speeds but the response to driver input is much faster and more direct, they will help to maintain stability by minimising and controlling body roll as long as the driving surface is flat and even. If however the surface is uneven or bumpy then the suspension is unable to comply with the changes and the tyre will skip and hop across the surface causing grip loss. Because the suspension is stiffer it requires more load to work effectively and really comes into its element at high speeds where the resistive nature of the springs helps prevent overloading the tyres.

    One of the quirks of GT's tuning/physics model is that it is almost impossible to roll a car as a result of it leaning over in a corner, this combined with not having to take real world issues like motion sickness into account means that we can exploit this to our advantage. One of the most common exploits is using ride height to increase grip at one end of the car of the other, the basic idea behind this is by increasing the ride height we increase the effective range of the suspension and gain grip. In the real world racing cars are always as low to the ground as they can be to reduce aerodynamic drag and to lower the cars centre of gravity which means the car is much less prone to rolling over during hard cornering, in Gran Turismo we don't have to worry about this so much. The aerodynamics aren't that complex either so we don't have to worry about spoiling them by running a relatively high ride height. However we will still find disadvantages to running the car at the top of its ride height so some common sense is still required, just don't be tempted into the usual mistake people make by lowering the car straight away.


    Our first practical step is to visually balance the suspension using the little blue bars located near the spring rate adjusters. Leave the front spring rate alone and adjust the rear spring rate so the little blue bar looks to be in the same position as the front, once that is done take the car out for a few evaluation laps and see how it feels. The next stage will be opening a new tuning tab (B) and copying your existing settings (A) over to it, once this is done increase the front spring rate on tab B by about 1/6th of the bar length and do the same to the rear. Test this and evaluate its performance against the standard model, if you feel it improved then keep increasing the overall stiffness by increments until you find where it performs best, alternatively if it feels worse after the first stiffening then try softening it instead. We are looking for the point where both the grip and the response feel adequate, we aren't really adjusting the behaviour of the car at this stage so don't expect it to suddenly go from understeering to oversteer or anything dramatic like that. Leave the ride height alone for the time being, we will adjust this later.

    Once you've found the sweet spot let me know what numbers you've ended up with :tup:
     
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  16. Blue_Impact

    Blue_Impact

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    Hello everyone I just stumbled onto this this thread and read the first page, I'd really like to get in on the tuning convo as well. I've been driving since gt4 but never fully grasped all the complex tuning of the game.

    it's okay to post questions and stuff about tuning here? I mostly run narrow touge tracks and could definitely use some advice on how to tune for it!

    thanks for posting all the info
     
  17. DolHaus

    DolHaus

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    Ask away :tup:
     
  18. speedy turtle

    speedy turtle

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    I’m happy with LSD configuration, by now, but if you think there is more to know… I’m all ears, I’m the pupil and you’re the master. I suppose we’ll need to go back to LSD before finish this tune.

    In any case, when we fihish with the Miata, I hope I’ll be able to count on your advice to configuring another and more powerful machine… not step by step, but at least to know if I go on the right way.

    I did the following modifications with the Miata’s spring rate. I’m going to relate my overall impressions, I don’t know if they’ll do any good, but here they are:

    I started with the standard configuration, 3,52/3,51; since the front and rear rate values are very similar, and I increased 1,25 kg. every time I went to track:

    SR: 3,52/3,51
    The impressions of the last post.

    SR: 4,75/4,75
    I didn’t feel much difference. 3 tenths faster.

    SR: 6,00/6,00
    I started to feel light more understeer. 1 tenth slower.

    I’m racing on Deep Forest standard track (the main straight ends on a turn to left). It is divided on three partial sections. It has four tunnels, two on the final of the first partial section, two on the final of the second.

    I continue going to orange the outside front tyre, but we’ve already talk about it:

    • Main straight final left hander turn. Very light orange.
    • First left then right hander turn just before first tunnel. Light orange.
    • Left-left hander turn before hill climb before third tunnel. Light orange.
    • Left hander turn before main straight. Orange.

    The rear tyres are another story. I can’t “burn them into orange”, but I hear them in that corners.

    SR: 7,25/7,25
    I started to feel light more understeer. 3 tenth faster than the SR 6,00/6,00 time.

    SR: 8,50/8,50
    My best time. 4 tenth faster than the SR 7,25/7,25 time.

    SR: 9,75/9,75
    In the same tenth than the SR 7,25/7,25 time.

    SR: 11,00/11,00
    Worse time.

    SR: 12,25/12,24
    Worse time than 11,00/11,00.

    In any case, of SR 6,00/6,00 onwards I felt something strange to a rookie. I don’t know if I’ll be able to explain:

    The car allows me to push the throttle before when I’m exiting the curve cause it seems to face better the exit: rear sliding, but then it increases the exiting radius: front sliding... Yeahhh!!! I’ve discovered a new concept: “oversteering-understeer”. :lol: :eek: :lol: :eek:

    I don’t know if I explained myself.

    Maybe oversteer is on the apex coasting and understeer appears just when I push the throttle on exit, but I feel both after I push the throttle.

    I suppose now is the moment to return to LSD, isn’t it?

    ST70
     
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  19. DolHaus

    DolHaus

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    The transition you have described is exactly what I was expecting although when doing this you should stop increasing the spring rate once performance starts getting worse, you've found the point where the tyres are unable to cope and now you know the upper extremes for this style/compound of tyre :tup:

    Our best results were between 6.0 and 7.25, the slight increase in understeer you experienced suggests that the front end is a little bit too stiff so try softening it slightly. The trick to homing in on the ideal solution is to keep halving your adjustments, I'll write a quick description of the process below:

    (imaginary car, feels too soft after initial test drive)
    4.0/4.0 - standard (+1.0)
    5.0/5.0 - improved (+1.0)
    6.0/6.0 - improved (+1.0)
    7.0/7.0 - worse (-0.5)
    6.5/6.5 - improved over 7.0 but slower than 6.0 (-0.25)
    6.25/6.25 - improved (+0.1)
    6.35/6.35 - worse
    6.25/6.25 - (-0.1)
    6.15/6.15 - improved (+0.05)
    6.20/6.20 - Improved

    You don't have to be this thorough every time, you'll get a feel for it after a while and it makes the whole process more fluid. The basic thing you need to keep in mind is that if your springs are too stiff you'll lose grip. The clue can come at either end of he car so expect understeer or oversteer at some stage, if you get understeer that means your front wheels have exceeded their grip limit, if you get oversteer then you have exceeded the grip limit at the rear. In either case you have learned a useful reference point and it tells us how to set that end of the car, it also means we can now start looking at the front and rear separately.

    In the case of out MX5 we've found the limit of the front end grip but the rear can still be further manipulated to begin to modify the cars characteristics. Leave the front alone and try increasing the rear spring rate separately and see if you find any gains. My expectation would be that the front end grip will improve on corner exit and then turn to oversteer as you keep stiffening, as before you want to stop when performance gets worse and start fining down your search. :tup:

    (if you do start getting throttle induced oversteer on corner exit then try reducing the LSD Accel a little bit just to check)
     
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  20. speedy turtle

    speedy turtle

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    Yes, I’d have stopped when the things started to go worse, but like it was the first time I did it, I preferred to go all the way to learn more about different reactions due to spring rate.


    Do you refer to leave the front where I found the best performance, around 7,00, or you refer to leave it at standard 3,50 and increase only the rear?

    Thank you.
     
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  21. DolHaus

    DolHaus

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    Check between 6.0 and 7.0 at both ends to see if you can find any more performance. Once you find where it performs best then leave the front end at that setting and work independently on the rear :tup:
     
  22. speedy turtle

    speedy turtle

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    I proved several configurations and finally I felt comfortable with SR F/R 5.75/7.25, maybe too much comfortable, but I think I’ll be able to modify that conduct later. It doesn’t mean I can’t drive a tighter car, but I was faster with a smoother configuration.

    I don’t know if playing with dampers could I fit with better numbers but, by now, these are the ones that I fit better with.

    ST70
     
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  23. DolHaus

    DolHaus

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    Sounds good to me, you never want to go to the extremes because it doesn't leave you with any wiggle room for the other settings :tup:

    Right, next plan is ARBs, these control body roll and how independent the two wheels on each axle can operate. If you were driving on a rally course and needed the wheels to suck up big bumps without affecting the others then you want to go as soft as possible (real rally cars don't actually run ARB's unless on tarmac), this allows the tyres to stay in contact with the road better but body roll is an issue. A car running on tarmac doesn't need the wheels to react to large bumps individually so we use the ARBs to control excess body roll and help distribute load between the tyres better.
    We will do the same basic testing procedure as we did for the spring rates, adjust both front and rear simultaneously and look for improvements or losses, try stiffening them first and see what happens. If you can't find any improvement then it may be that your springs are already controlling the body roll adequately, keep this in mind and perhaps try reducing the spring rates a little and trying with stiffer ARB's instead, this won't always result in improvement but its worth checking.
    If you do find improvement by just tweaking the ARBs then follow the same procedure where you start adjusting front and rear independently and observing the effects. The affects should be similar to spring rate adjustments in that you will adjust the front/rear balance, a stiffer rear is more prone to oversteer and a stiffer front is likely to create understeer
     
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  24. speedy turtle

    speedy turtle

    Messages:
    108
    Thank you DolHaus. I'll test it.


    Excuse me, normally I don’t like to mix different subjects, but like there is a new seasonal that implies 600PP Italian cars and I’d like to use a 4WD car, it generates new doubts to me.

    When you tune a 4WD car, must you adjust independently the rear LSD settings from the front settings, like we do with the suspension, or are they closely related?


    ST70
     
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  25. DolHaus

    DolHaus

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    Location:
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    Good question, the operation of the LSD is the same no matter which end of the car its at so we use the same basic process to tune it. With a 4wd system you have to keep in mind the basics of tyre theory - the tyre has limits and to get the most out of it you need to stay within them. These limits are defined by the amount of energy that the tyre can resist before traction is lost, this energy come in the form of linear and lateral forces. Linear forces are roughly defined as those encountered when accelerating or decelerating in a straight line, lateral forces are those encountered when trying to change direction. These forces and the tyres ability to resist them are not separate entities, if you put more linear force through a tyre then you reduce the amount of grip available for changing direction (lateral).

    In a RWD car the split is fairly simple, the front wheels aren't receiving much linear force (unless braking) so they are more capable of changing direction, the rear wheels have very little lateral force acting upon them so they have more grip available for accelerating. In a 4wd car the front wheels are also responsible for delivering drive so there is less grip available for changing direction and they will always understeer when compared to a RWD. However if the RWD car is packing a lot of power then the rear tyres may not be able to cope with all of it which leads to grip loss, a 4wd packing the same power will do a better job of putting the power down because the force is spread across 4 tyres rather than 2.

    With this in mind it becomes easier to see how we should tune our differentials, we want to spread the linear forces in order to allow us to put the power down onto the road but we want to keep the amount going to the front wheels to a bare minimum in order to maximise cornering potential.
    It will be a case of balancing the Torque distributing centre differential against the front and rear LSDs, to do this we first need to put a sensible base tune on our LSDs. I would start with something like 10/15/10 on both ends and see how that feels, if the car is not showing any obvious signs of fault* then its time to move onto the centre differential.

    *
    Understeer/general instability - Initial too high/low
    Outside/inside wheel lighting up under hard acceleration - Accel to high/low
    Unable to rotate/unstable during hard braking - Decel too high/low

    With this basically set you should start to adjust the TDCD and see where the car feels and performs best. The basic idea is that the more power you send to the rear the more grip you'll gain at the front so the faster you'll be on corner entry and apex, the downside is that you'll be less capable of accelerating out of the corner upon exit so its a case of finding the best compromise.

    The separate LSD settings on a 4wd are generally less critical than a 2wd car but that doesn't mean there aren't advantages to be found. Generally I tune my front LSD to be slightly more open (lower numbers) than the rear as this will help to keep the car feeling lively but there have been instances where having the front Accel higher than the rear has allowed the front end to pull the car out of slow corners so its worth trying. As a general rule I will never set the front Initial or Decel higher than the rear as this will just make it harder for the front wheels to dictate the direction of travel if they aren't able to follow as tight a radius as the rear.
     
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  26. speedy turtle

    speedy turtle

    Messages:
    108
    Hello Dolhaus:

    I'm here again. I've been a little busy this week but finally I could test the ARBs last night for a while.

    I found opposite sensations and I don't know what to do. I mean:

    I did the best time with ARBs 7/7, but
    I feel the car smoother with ARBs 3/4.

    The differences on time are little but when we talk about speed, any tenth counts.

    What do you think?


    Thank you.
     
  27. DolHaus

    DolHaus

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    What do you mean opposite sensations? Please try to explain what you are experiencing, a basic run down of what you think the car is doing well and where you think it's losing time would be great :tup:

    The car will be more precise at 7/7 but the margin for error will be reduced as you will reach the grip limit for the tyres more quickly during cornering. At 3/4 the car will feel more compliant and more forgiving but you won't be carry as much corner speed. Have you tried 6/7 or even 5/7?

    It is very unlikely that you will find large gains in performance at any point after taking care of the basic showroom problems (suspension/LSD/transmission), a few tenths here and there is the best we can hope for but it all adds up. The MX5 isn't a bad car straight from the showroom so we're never going to see huge or obvious improvements but we use the same approach whether we are just polishing an already good car or taming a twitchy monster, adjust one thing at a time and note the results.
     
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  28. speedy turtle

    speedy turtle

    Messages:
    108
    Yes you're right, sorry to be so imprecise.

    I mean that I feel more confortable with ARBs 3/4, the car’s not so nervous, but it’s true, I’m not on the edge and my time wasn’t so good. With ARBs 7/7, it goes on the edge and it’s easier to make mistakes, I have to be more concentrated… obviously if I’m trying to drive fast…

    In any case this last weekend I was testing the car again and I’ve improved with higher ARBs, the problem is that I’m not be able to feel differences between 6/6, 6/7 and 7/7. If we only consider the lap time, the best would be 6/7. The differences are two tenths as much.

    Since I started with the “standard” car I’ve improved a lot, but it’s not the car… it’s me. Before this intensive training, I only gave grope, but now at least I know why I do what I do, and yes, I’m following to the letter your instructions about “one thing at a time”.
     
    Last edited: Sep 26, 2016
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  29. DolHaus

    DolHaus

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    3,865
    Location:
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    It won't always be a big change, if you can't make your mind up about which is better for you then copy the settings to another tab and have one set up where it felt best and one where it was fastest. This will allow you to continue developing the car but gives you a reference point you can jump back to if needs be.

    We will now move onto the dampers, we will work on the car with 3/4 ARBs as it is more likely to show development. The dampers have a huge effect on weight transfer behaviour and can be used to make some fairly serious changes, they don't really work like real life dampers in GT6 but this is to our advantage.
    I will need a fairly detailed description of how you feel the car is behaving during key stages of weight transfer as these relate to particular pairs of dampers.

    The important weight transfers are -

    Braking on corner entry
    Releasing brakes and turn in
    Mid corner (neutral throttle/brake)
    Applying throttle while steering
    Corner exit
     
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  30. speedy turtle

    speedy turtle

    Messages:
    108
    Ok, I'll test it on ARB's 3/4 and I'll try to be detailed with my impressions.

    One question about something that breaks my schemes. If dampers have a great effect on weight transfer, why we started configuring ARBs before dampers?


    Thank you.