How to tune

Discussion in 'GT2 Settings & Tunings' started by gt2kid, Mar 30, 2002.

  1. gt2kid

    gt2kid

    Messages:
    65
    This thread is intended as sort of an instructional guide to tuning cars in gt2.
    I will not be able to post the whole subject right away due to it's complexity. I will attepmt to cover everything that I have figured out about it in short manageable posts.

    If you have any questions or comments, please do not post them in this thread. I would like to keep it intact for printability when it's finshed. Instead, start a new thread with your question/ comment.

    Thanks and I hope you find this useful.
     
  2. gt2kid

    gt2kid

    Messages:
    65
    Everything done in this game (driving, tuning, car selection, etc.) revolves around one simple concept: Maximizing the efficient use of your tires. In order to use the tires effectively in this case, the workload (aceleration in any direction) must be evenly distributed across as much rubber as possible. The tires doing the work should have as much pressure as possible holding them to the road to maximize their traction. This concept is very diferent from real life, but I didn't write the code.
    Although this goal is a simple one, you will find yourself testing constantly. This is because GT2 does not give us all the information we need to calculate the settings.
    To tune effectively, you will need a baseline setup, good recordkeeping, an effective testing strategy, and a thorough understanding of what each adjustment does. Testing and tuning within thee guidelines will give you a "generic" setup, not optimized to any particular track. Several settings need to be adjusted to suit any particular track.

    First order of business is to come up with a baseline setup.
     
  3. gt2kid

    gt2kid

    Messages:
    65
    To baseline any car, you will need access to as many variables as possible. Obviously you can't tune a car without anything to adjust.
    Some adjustable components are better left on the shelf instead of on your car. I have found the yaw control to be a colossal waste of money.
    You should ideally also have another copy of the car with the game's settings untouched. Ths car will serve as a reference so you can gauge your progress. I like to have one set of rims on my "yardstick" car and a different set of rims on my race car. This way I can tell them apart in the garage.

    My baseline setup looks like this:

    -Springs: Front 2.0/Rear 2.0
    -Shock bound: Front 1/Rear 1
    -Shock Rebound: Front 2/Rear 2
    -Camber: Front 0.5/ Rear 0.0 (This assumes a rear wheel drive car. For FF or 4wd cars, the rear setting is 0.5)
    -Toe: Front 0/ Rear 0
    -Antiroll Bars: Front 4/ Rear 4 (This assumes an average weight car. I use 3/3 for very light cars and 5/5 for very heavy cars.
    -Ride Height Front Min/Rear Min

    Transmission:
    Auto set to 10
    1st: set minimum (numerically lowest or tallest)
    Final: set minimum (usually 2.5)

    Brakes: Front 21/ Rear 18

    Aerodynamics: Front Highest setting/ Rear=Front+10

    LSD: Initial 1/4 maximum
    Accel 1/2 maximum
    Decel 0

    TCS: Maximum

    This is enough to serve as a starting point. Tomorrow I'll walk you through the first adjustment, the gearing.
     
  4. gt2kid

    gt2kid

    Messages:
    65
    Your first step in improving your handling is to adjust the torque you're laying down to the track coming off the turns. I can't tell you how many times I've heard that high powered RWD cars are "uncontrollably loose". In reality, most of these cars understeer. The problem is wheelspin. Obviously, if you're smoking the rear tires, they cannot grip a turn. Once you get this problem under control, these cars become much faster.

    Take your car to any convenient track for a time trial.
    The first step is to look at your "dyno sheet". This is visible in the settings menu whenever an engine component is highlighted.
    Note the RPMs at which your torque peak and Hp peak occur. You will be adjusting your transmission to drop to the torque peak when you shift.
    Some cars have the Hp peak at a much lower or higher RPM than redline. Ideally you should be shifting gears at an RPM a little higher than the Hp peak. This is not always possible, but learning to manually shift can help with many cars.

    After noting the RPMs that frame your "powerband", take the car out on the track and bring it to a complete stop. Hold the brakes and gas simultaneously in first gear. Release the brakes. Note how the tach behaves. If it hits the rev limiter, your gearing must be taller. If it bogs, your gearing must be shorter. You're looking for the tach to float in the middle of the powerband until the tires "hook up", at which point it climbs to redline.
    To make the gears taller, go back in the settings menu. Go to the transmission settings menu and highlight but do not select[\i] one of the ratios. Press start. This will reset the gearing to the stock setting.
    Now select the auto setting. Adjust it to a higher number, say 15. Go back in the individual gears, setting 1st and final to the lowest number available. You would similarly go numerically higher ("shorter") if necssary via the same procedure.
    Repeat your test on time trial. This will take quite a few runs to dial in exactly right.
    There may be some problems encountered during this procedure. Your engine may be so powerful and/or tracion so poor that first gear may be useless. If this occurs, you may be forced to start out in second or even third gear in order to get the proper initial gearing. If this occurs, the car absolutely must be shifted manually.
    Another problem occurs at the opposite end of the spectrum; the car is so weak or has so much traction that gearing it short enough for a proper "haze" leaves you unable to reach your top speed on the track. If this occurs, it is more important to reach your top speed. Adjust accordingly.
    For now, evenly space the rest of the gears. We will fine tune them tomorrow.
     
  5. gt2kid

    gt2kid

    Messages:
    65
    There are alot of differing opinions on how to poperly adjust your gearing. My method involves setting the gearing to the car and adjusting it (if necessary) to the track.
    Contrary to popular belief, a close ratio transmission is not necessarily better than a wide ratio transmission. Similarly, having 7 gears is not necessarily better than having 4.
    The number and spacing of the gears is a compromise. Having more gears slightly increases your average power during a lap, but it forces you to shift more often during a lap. The act of shifting gears takes a finite amount of time. Depending on your collection of parts, it could take anywhere from .05 to .15 seconds. This may not sound like much, but after shifting your way around a road course, it adds up.
    Luckily, this is one of the problems we can solve mathematically. Unfortunately, the game rarely allows us to implement the "perfect" solution, since it gives us a narrow window for each gear adjustment.
    The car's acceleration in any individual gear at any RPM is a function of it's torque. The more torque you have, the faster you will go. Obviously, there is no reason to operate at an RPM below your torque peak (you wrote it down, remember?) during a lap. This sets the lower limit for your powerband.
    The upper limit is a little more vague. Your torque is declining as the RPMs climb. At some point, you'd be better off in another gear. You're looking for the point where this occurs. Since the compromise is a function of torque and RPM, we would need a measure of torquexRPM. This turns out to be Hp. It would appear that shifting at the Hp peak is the ideal solution (in many cars it is) but since you lose some time during the shift, it's quicker to let it wind beyond the Hp peak. I wouldn't go any farther than 10%. This means that your upper limit is either just shy of the rev limiter or just above the Hp peak.

    Now that we have both limits, we want to find the gears that will drop our RPMs from the upper limit to the lower limit during a shift. The first step is to divide the upper limit RPM by the lower limit RPM. This gives us the drop ratio. Now multiply this number by your first gear ratio. This gives you the ideal second gear ratio. Multiplying the drop ratio by the second gear yields the ideal third gear ratio, and so on.
    The problem is that the game will most likely not allow you to set these ratios exactly where you want them. In the case where you can't set the ideal ratio, set your gear as close as the game will allow, then calculate from that ratio to find the next gear.

    In the case of some cars, you may end up with final gearing that is so short, they end up hitting the rev limiter on the straightaways. Those are the feeble, torqueless cars that rely too much on gearing to generate torque. Should you end up with one of these lemons, you will have to work backwards from the expected top speed, multipying the drop ratio to find the next lower gear and so on. These cars must be re-adjusted for each track.

    Now that we've set the gearing for the car, it's time to adjust the handling. In order to do that, you must know what each setting does to the car. I'll start with the springs.
     
  6. gt2kid

    gt2kid

    Messages:
    65
    Each component in your suspension has a specific function to perform. Very often, people will compromise this main objective to gain a side effect. Often, this side effect could have been achieved by other means without destroying the handling of the car. Try to keep this in mind as we go through each adjustment.

    Another note: Springs follow their own odd logic in this game. Real life is very different.

    Springs:
    Hours of skidpad testing have shown that stiffer springs corner better than softer springs so long as the tires can maintain contact with the road.
    The main function of springs is to maintain this contact. Too stiff and the tires will lose contact with the road after bumps. Too loose, and the frame will bottom out, causing the tires to lose contact.
    This means that there is a range of acceptable spring rates for each car.
    The lower limit depends on the car's ride height and downforce, whereas the upper limit depends on the track's smoothness.
    A generic setup will show the softest rate that will suffice to keep the frame off the track. This may be stiffened considerably depending on a specific track's smoothness.

    A couple of side benefits of springs are their roll resistance and ability to alter roll couple distribution. These are side effects; the primary objective should never be compromised in search of these effects. (More on these concepts later).

    For a generic setup, the adjustment is straightforward:
    Take the car to any convenient track with a decent straightaway. If the car bottoms out at the end of the straightaway, stiffen the springs. Once the car stops bottoming out, try softening one end to see if the car bottoms out. You are looking for the softest springs at each end that will keep the car off the ground.

    Any time you adjust the springs, the shocks must also be adjusted. More on this next.
     
  7. gt2kid

    gt2kid

    Messages:
    65
    Shocks have to be among the most abused components in the suspension. They are almost universally misadjusted in the attempt to improve handling. This is a shame, since they're one of the easiest components to set correctly.

    The purpose of the dampers is to control bouncing. They must be adjusted correctly to ensure that they do their job, yet are not so stiff they keep the suspension from articulating.

    Shock settings are divided into 2 adjustments: bound and rebound.

    The shock compression setting is meant to control the wheel assembly's tendency to bounce on the spring (patter). In the game all wheels weigh the same. Thus, compression is strictly a function of spring rate.
    The shock compression setting should be equal to .5x the spring rate.

    Likewise, it's the extension setting's duty to control the car's tendency to bounce (wallow). This setting is affected by the car's weight and the spring setting.
    A good starting point is to set the extension to (weight/1000)* spring rate. This usually works out to approx. 3x the compression setting.

    To test and adjust your compression setting, take the car to a fairly bumpy track. Run a few laps and observe the replay. If you cycle through the external views, you can observe each wheel independently. You want to watch the tire and it's shadow. They should move together. Try to set the softest compression that will allow this.

    The procedure for setting extension is very similar, except this time you're looking at the car vs. it's shadow.

    Try to make one change at a time and observe just the effect of that change. Also keep in mind that when you adjust the springs, the shocks must be re-adjusted as well.

    Next, we'll cover camber and toe.
     
  8. gt2kid

    gt2kid

    Messages:
    65
    Camber is the angle at which the top of the tires lean inward at rest. 0° means perfectly vertical, and any angle greater than that is inward.
    The camber adjustment exists to equalize the load distribution across the tires. For example, during straight line acceleration and braking, your tires should have 0° camber so that they sit perfectly flat. Otherwise, you're throwing away traction.
    Things become a little more complicated during cornering. During a turn to the left, the car will lean right. When this happens, the tires also lean right. Adding the right amount of negative (inward) camber can cause the right side tire to sit vertically during cornering (It's doing almost all of the work), thus maximizing cornering grip.
    Your perfect caber setting is a compromise between best acceleration/deceleration and cornering. For any track, best acceleration and braking will be had by setting camber to 0/0.
    Best cornering will be had by setting camber to equal whatever angle the body rolls to during turns.
    The compromise comes into play when you optimise the camber to the track. Which axis of acceleration is more important? This varies from track to track.
    To find the best camber for cornering, you will need to access the skidpad (more on this later) and test. The front should be adjusted to create as much oversteer as possible, and the rear should be adjusted to create as much understeer as possible.
    No real benefit comes from exceeding this maximum value. It can take away traction to equalize a car, but that is the wrong path.

    TOE

    Toe is a very straightforward concept. It is the measure of how much the front tires point towards or away from each other when viewed from above. Toe in means the fronts of the tires are closer together than the rears. Toe in is expressed as a negative distance.
    Changes to the toe affect the stability of the car. Toe in causes the front tires to push towards each other, resisting changes in direction. Likewise, toe out causes the tires to pull away from each other and resist traveling in a straight line.
    Toe in adds stability and reduces agility. Toe out adds agility and reduces stability.
    This setting is strictly the driver's preference. If you notice that the car is too "twitchy" on the straightaways, reduce the toe. If the car changes directions too slowly, add some.

    Next, We'll cover Antiroll bars (a.k.a. sway bars).
     
  9. gt2kid

    gt2kid

    Messages:
    65
    Antiroll bars are somewhat like springs. The difference is that they have no effect on ride harshness. They resist body roll, yet do not resist vrtical movements.
    The primary function of antiroll bars is to provide roll resistance, thus freeing your springs from this task. If you were to try to use the springs for this function, they would become far too stiff to follow the irregularities of the track.
    A side benefit of these is that you can tune them to create roll couple distribution (more on this later).

    Contrary to popular belief, there is no such thing as "too stiff" antiroll bars in this game. Feel free to set both ends at 7 if you wish. You may want to trade off some roll resistance at one end to create understeer or oversteer.

    Next: Ride height
     
  10. gt2kid

    gt2kid

    Messages:
    65
    This is exactly what the name implies.

    Lower ride heights tranfer less weight during turns, thus increasing cornering G. In RWD cars, More weight transfer is desirable during acceleration in order to help plant the rear tires.
    The lower you set your ride height, the stiffer your springs must be. This is due to the reduced range of motion of your wheels. Otherwise the car will bottom out over bumps. If you stiffen your springs, your shocks must follow suit.
    You can see that there is a practical limit for every track on how low you can set ride height. For the generic setup, go no lower than 80. This will have to be adjusted for each track.

    I believe this covers all the options in the suspension menu. Next is the brakes.
     
  11. gt2kid

    gt2kid

    Messages:
    65
    The higher the number, the tighter they grab. Too tight and they will lock up the wheels, resulting in decreased braking and loss of control.
    The front brakes handle the majority of the work in all cars. This is due to forward weight transfer during deceleration. The more nose heavy (FF) the car is, the more of the braking will be performed by the front brakes.
    The simple test for setting front brakes is to visit the test track. Accelerate to more than 100MPH. Apply the brakes and press pause. Pause repeatedly until the speedo reads exactly 100. Note the time. Un pause the game while still holding the brakes. Pause again at 50. Note the time. The difference in time will show your braking effectiveness.
    You want to set the front brakes to perform this test in as little time as possible. If you notice smoke during this test, your brakes are too firm.
    Setting the rear brakes is a matter of personal preference. They sould never be set higher than the front, bt they may be close, depending.
    A stiffer rear brake setting will result in oversteer when trail braking (turning and braking simultaneously). This can be very useful, but some drivers find it unsettling.

    Next, Downforce
     
  12. gt2kid

    gt2kid

    Messages:
    65
    Downforce is easier to adjust in this game than in real life. Let me begin at the beginning.
    Tires generate more cornering force when more downforce is applied to them. Aerodynamic downforce is pretty much a freebie in this game. It makes your car turn better without adding weight to carry around the turn. It does, however, add drag. In real life, doubling the speed will add 8x the downforce and 8x the drag. In this game, both merely double. Unless you're running a max speed time trial, your best bet is to set front downforce to maximum. This will dramatically help your cornering and braking, and only marginally affect your top speed. Net effect: positive.
    The rear downforce is set to driver's preference. It will be somewhere in the neighborhood of front downforce. Since downforce varies with speed, any front-to-rear difference in downforce will also vary with speed. This makes the rear downforce a tuning tool; If your car is well balanced at lower speeds but loose at high speed, you will want to add some rear downforce.
    I prefer a certain amount of understeer at high speed to ease my workload and add stability. Therefore, I'll usually set it to front+10.
    Next: Limited Slip Diffs
     
  13. gt2kid

    gt2kid

    Messages:
    65
    Tires have many factors affecting how well they grip. Limited Slip Diffs (LSDs) affect the property of Static vs. Dynamic friction.
    One of the properties of rubber is that it is dependant on slip. It generates near-maximum grip when not slipping in relation to the ground. It's grip is improved when it slips slightly (no smoke). When it slips enough to generate smoke, it's traction is reduced. The more it smokes, the less it can grip.
    Differentials route the power to both drive wheels. When one wheel slips, more power is routed to the slipping wheel, thus reducing the ability to accelerate.
    LSDs counter this by coupling both wheels together. Problem is, the coupling of the wheels together hampers their ability to turn because they can't rotate at different speeds.
    Thus increasing the setting of an LSD will induce understeer in this game. The higher the setting, the more understeer.
    This is useful for balancing the car at different stages of a turn; entry, mid-turn, exit.
    You're decelerating on turn entry. Thus, adjusting the LSD decel can add or remove understeer during this phase. Mid turn is affected by the "coast" adjustment, and turn exit is affected by the "accel" adjustment, keeping in mind that 2 tires accelerate better than 1. (or 4 better than 2).
    This is a powerful tuning tool. To use it, adjust the car loose, then add understeer as necessary with these adjustments. This will have a dramatic effect on the car's handling.
    Next: Traction Control
     
  14. gt2kid

    gt2kid

    Messages:
    65
    Traction controls sense wheelspin and reduce throttle to eliminate it. If you have it, set it to maximum. This will allow you to run slightly deeper gearing without blazing the tires.
     
  15. gt2kid

    gt2kid

    Messages:
    65
    Now that you know what every adjustment does, it's time to move on to the hard part; how to apply this information.
    Tuning involves alot of troubleshooting. When the car is doing something other than what you'd like, somehing must be changed to correct it's behavior. The difficult part is deciding what to change.
    I can't give you a step-by-step guide on how to do this, but I can give you guidelines to work within. This should help you make reasoned decisions as opposed to guesses.
    #1 Know your enemy. You must know exactly what the problem is you're trying to fix. Start with the basics and fill in the details as you think about it. Is it understeering or oversteering? Smoky Yunick (tuner god) once said "The difference between oversteer and understeer is which end of the car hit the wall first."
    If it's understeering, when does it understeer? All the time? on turn entry? Only in the middle of bumpy high speed turns? Paying attention to when a problem shows up and when it doesn't can guide you to the best solution.
    #2 Avoid crutches. If your car is loose, the answer is not to make the front tires slide more! This will make the car neutral, but it won't have any cornering ability either. This approach is "crutching" and masks one problem by introducing another one. If you have a problem, don't hide it; fix it.
    #3 Killing two birds. If you have two separate problems that can be fixed with one adjustment, use it.
    #4 Parts abuse. I touched on this one earlier, and it's kinda related to #2. Each component has a specific job to perform. If it is adjusted to the point that it can't fulfill it's primary duty, it will introduce a whole slew of problems.
    More to follow....
     
  16. Korndawg

    Korndawg

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    380
    wow... how long did it take you to put all that up :sick:
     
  17. Parnelli Bone

    Parnelli Bone Premium

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    For sure! Anyone who thought i had a big cybermouth hasn't met the likes of GT2Kid!
     
  18. Korndawg

    Korndawg

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    380
    :lol: :lol: props to him though for spending all that time to help ppl out. i cant say id do it myself :scared:
     
  19. Parnelli Bone

    Parnelli Bone Premium

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    And he wasn't even done yet! His last sentence for this monologue was “more to follow”. Gotta admit he has some interesting notions. I plan on trying some of them out, tho in the end i'm sure i'll stick to my intuitive method of tuning.
     
  20. flamingwonky

    flamingwonky

    Messages:
    406
    Props to the kid! :crazy: Lots of work put into that!
    My tuning: minimize ride height, camber out the wheels ~4.5*, rims, done! ;)
     
  21. sucahyo

    sucahyo

    Messages:
    2,171
    when facing identical car on manufacturer's event using the lowest final gear (2.5) always get me faster acceleration than other car, even when using auto setup
    my simple setup is:
    - final gear 2.5
    - auto setup to maximum speed I want
    - vertical line up the gear