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Advanced Tuning Guide


The current generation of video game consoles is the 7th generation, which began with the release of Microsoft's Xbox 360 on November 22, 2005. This was followed by the release of Sony's PlayStation 3 on November 11, 2006, and Nintendo's Wii on November 19, 2006. Unlike the PC, when a console gets released its hardware is locked in, and historically starting with the release game studios begin with a general approach to taking advantage of the capabilities of a console but only later begin to leverage its full capabilities. With the current generation now six years old you might think that there are no new tricks up developers sleeves, but the release of Forza 4 for the Xbox 360 by Turn 10 clearly proves that is far from true.


While the Autovista part of Forza 4 may feel like more flash than substance, the incredible leap forward that the game world represents is anything but flash, and considering that the Forza games have always been more simulation than racing game, their willingness to squeeze every bit of capability out of the aging Xbox 360 has resulted in a new entry in the well-loved series that is every bit the worthy successor to the mantle established by the previous games.


While every effort has been made in preparing this material to make it as complete and helpful as possible, in view of the fact that it is being written for an audience of gamers who may not necessarily be proficient in the math and technical jargon that is particular to the automotive industry and auto racing, the language that is used in this guide has been carefully chosen to make it as easy to read as we could manage.


We address each element that is considered in the process of tuning, with an emphasis upon the hand's-on approach that is celebrated part of the Forza series. While the process of tuning can be highly technical, you may find that it is very helpful to test out different approaches as you work them out so that you can better understand the effects that the changes you are making to your car actually have on it. There is no substitute for experience in tuning, and the best way for you to gain that experience is by doing, by experimenting, and by teaching yourself. This guide will help you with all of that.


Before you begin any tuning adjustments you need to spend some time in the game learning the telemetry system and what the different readings mean. You need to be very familiar with it because it is the key to determining both the state of the element being tuned as well as the state of change as you begin charting the differences.

 


Advanced Tire Tuning


One area in the game that was given considerable focus and polish is the technical side of the auto, from physics to mechanics and, perhaps of more interest to players, a willingness on the part of Turn 10 to throw out entire parts of the existing game model in order to improve the experience of play by replacing those sections with new content that takes advantage of science and engineering knowledge that was not previously available to them. In particular this includes tires; the team that programed the tires in Forza 4 started from scratch, enlisting the aid of actual manufacturers, who provided unprecedented access to information on performance and physics characteristics that all of the companies that make tires today consider to be confidential information that they go to some lengths to protect.


The tires on a car are a critical element in the chain of technology that is of interest to tuners; put simply, you can actually obtain significant improvements across the board simply by choosing the best tyre for a given track! Professional tuners include the tires in every calculation that they make in the process of tuning, from the motor to suspension, and even body tuning, because that relatively tiny point of contact between the rubber and the road is really what the entire process is about.


With that consideration in mind, the first section for this advanced tuning guide deals with the tires, as that is logically the first and best place for you to start in the process of tuning your car to improve its handling and performance.


Tire Pressure


The air pressure in your tires represents the single most significant influence upon the elements of grip, responsiveness, and wear -- the simple act of adjusting the pressure for specific conditions has an easy to feel and recognize impact upon performance and grip that is obvious to most drivers. Part of this awareness is likely due to the public service programs from the 1970's to today reminding drivers that keeping their tyres properly inflated has a profound effect upon their gas mileage.


While this is an obvious way to influence performance it is also an aspect of tuning that is problematic because many racers try to implement it by eye and feel rather than scientifically. The practice of adjusting pressure in this fashion actually causes more harm than good in both the short and the long term, because of the common misunderstanding of how it applies to racing.


Tyre pressure is always adjusted with the tires in the cold state -- meaning that they have not been driven and thus have not built or retained heat. The reasoning behind adjusting the pressure in a cold state is that it allows the actual pressure to be more accurately measured; adding pressure to a hot tyre lacks the consistency and predictability because the pressure is not going to be the same in each tyre due to the way that heat affects the measurement. So unless all four tires are exactly the same temperature -- an unlikely event -- so that the actual pressure in each -- regardless of how it appears when it is gauged -- will invariably be different, which can apply a negative result.


The reason that this is an issue has to do with the reasoning behind pressure adjustment in the first place, which is not some arbitrary process but is well-grounded in science. Each track you race on has different characteristics and will exert different types of force upon your tires, and that is why you adjust pressure for the specific track. It is not a generic process.


For example under normal driving conditions -- on streets and highways not on tracks -- the ideal pressure to obtain peak friction is generally accepted to be 32 psi -- of course this is a generalization but it is one that has been established through judgment of performance in real world settings. The ideal pressure on a given track is a specific number that is arrived at through examination of temperature and performance characteristics and not a generalization at all.


Examining the temperature conditions is the primary component in determining what adjustments need to be made to pressure, so to recap you start from a cold state, make your estimated adjustments to pressure, and then take the car out on to the actual track you are adjusting for and run three or four laps so that you can then examine the heat characteristics to further refine your adjustments. After you run the laps, replay the run and bring up the telemetry so you can watch the changes.


Properly Adjusting Pressure


The best tool that we have in judging the results of adjustments to tire pressure is the telemetry readings that are available in the game, which provide a very accurate picture of the current state of each tire and, through extrapolation, what we need to do to obtain the best results. The primary objective is to configure them so that after they heat up they provide the best grip range possible.


After testing by running laps, you examine the current state of the tires immediately following the test laps to determine what steps to take next. On thing to bear in mind when testing is that the Peak Grip Temperature is between 180 and 210 degrees, so you should be reaching that area for every test and if you are not, add laps until you do.


If you find that the tire edges are hotter than the center after testing, this indicates that the pressure is too low. The general formula in correcting this is to add 1 psi for each 5 degrees of difference. Conversely when you find that the center of the tire is hotter than the edges, this indicates that pressure is too high, and the standard formula is to reduce pressure by 1 psi for every 5 degrees of difference.


During testing if you experience pronounced handling changes, evaluating tire temperatures often reveals the cause of this effect. When you find that there is significant difference between the temperature in the front and rear tires (which can cause over or under steering), the primary culprit may well be tire pressure, but it can also be the tire itself, which may be either too narrow or too wide, or even the suspension (if you have adjusted it recently) which may be too stiff or too loose.


Correcting the problem by adjusting the suspension is one option, but since you are in the process of determining your optimal tire pressure for the track, you want to begin there and not jump to a different area of tuning straight away as that often creates more problems and can cloud the actual cause of the problem, making your job ten times more difficult.


Altering Tire Width


If you are testing because you have changed the tire configuration on your car -- specifically if you have selected tires with new width characteristics, the likely cause for this new problem is either the pressure or the width of the tires -- but more likely the width -- so if you do not plan to adjust the suspension during your tuning you may want to start over with a different width that is perhaps less extreme a change. Bear in mind though that adjusting the suspension often solves these problems...


When the front tires are hotter than the rear tires, either the front tires are too narrow or rear tires are too wide. This situation will cause the car to under steer, so if the front pressure is not too high it is likely that there is too much front spring sway, not enough rear spring sway, so you may want to adjust the front spring and sway bar, stiffen up the rear spring and sway bar, or decrease the front pressure or increase the rear pressure.


When the rear tires are hotter than front tires your car will over steer, and this is generally caused by the front pressure being too low or the rear pressure being too high. It can also be caused by the rear tires being too narrow or the front tires being too wide. If correcting the pressure fails to provide relief or causes more problems than it solves, the obvious solution is to adjust the rear springs and sway bar to be softer, or to stiffen up the front springs and sway bar.

 


Properly Configuring Tire Camber


Camber angle is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear. It is used in the adjustment of steering and suspension, and is a particular focus for tuning. When the top of the wheel is farther out than the bottom, we call that positive camber, and when the bottom of the wheel is farther out than the top, we call that negative camber.


Camber angle adjustments alter the handling qualities for your suspension configuration in specific and predictable ways. For example you use negative camber to improve grip while cornering, so a track with a lot of cornering in its profile would be one in which you would want to adjust negative camber in your tuning plan. If the track includes more straight sections than cornering you would want to adjust for zero camber, because the greatest traction for maximum straight-line acceleration will be attained zero camber angle, so that the tread is flat on the road. If you are tuning for rally racing that includes a lot of off-road and dirt surfaces, you would use positive camber to help achieve a lower steering effort.


When evaluating the camber adjustments you have made, if the inner edge of the tire is hotter than outer edge, you have too much camber and you need to decrease the negative camber, but if the outer edge is hotter than inner edge, there is not enough negative camber, so you need to increase negative camber.

 


Brake Tuning


Properly configuring the brakes on your car is a key element in handling and performance -- but you know that. When you begin altering the brake setup this will primarily consist of adjusting the balance of braking power between the front and rear wheels, or what is called brake bias.


This is represented by the percentages applied to each, for example a brake bias of 70/30 means that the front brakes are given 70% of the total braking power, while the rear brakes are given 30%. This is a critical setting because it effects handling while cornering, as well as your driving style.


Adjusting the brake bias toward the front makes your car more stable while braking as you enter a turn; if you shift the brake bias toward the rear the car is looser while braking and entering a turn, which can make it less stable. If that makes it sound like giving the car more brake power in front is always best, bear in mind that too much brake power in front can actually hurt your performance and control, because it can result in the brakes locking up. Generally speaking the idea is that the front brakes are used to alter control of the car in turns, while the rear brakes are used strictly for stopping power. Of course none of that applies to setting the car up for drifting, which tends to use the opposite settings.


Your car should always have more front braking power than rear, since the mass and weight are transferred to the front of the car during braking, and with brake bias towards the rear, the car is increasingly less stable because the rear tires will lock when the weight shifts forward.


You may find that the Anti-lock Braking System (ABS) significantly interferes with your handling and performance in turns, so it is a good idea to turn that off before you begin tuning the brakes and tires. In addition to that, you will need to decide what setting you will use for brake pressure -- the choice you make being consistency. Try each of the three settings and decide which works best for your style and then stick with the one that works for you so that you improve with it, rather than having to learn a new handling style.

 


Differential


The Differential settings control how your car applies its power and torque to the road. In modern cars with automatic differential control this is accomplished by applying more power to the stable wheels, which usually means the outside wheels in a turn.


The setup for racing is the opposite, with power being sent to the inside wheels, which is a product of the frequent and extreme turns. The important setting here is the slip rate, which many drivers set higher because it improves speed and stability coming out of turns. There are two settings to be concerned with -- Acceleration and Deceleration.


The acceleration setting controls when the differential locks while under power, and setting it to a higher percentage has the effect of preventing individual wheels from slipping. This allows you to use more power when exiting a corner, but can make the car less stable. Reducing the percentage has the effect of adding stability in the middle of the turn, but you exchange power on the exit for that stability, so it is a balancing act. There is also a decided impact based on your driving style and skill as well, which means that there is no magic number that will work for everyone -- which is why you tune, right?


Themost effective way to find your personal sweet spot is to start with a higher slip rate, and then do test laps to see how easily you lose control of the rear end in the middle and end of turns, and then adjusting the number down until you find your balance between stability and speed. There really is no point to having massive stability of you cost yourself speed, especially considering that in Forza 4 you will be doing almost ALL of your passing in corners!


The deceleration setting controls when the differential locks when you are not under power, such as when you are entering a turn. Setting it high here will add stability but at the cost of agility. Staring with a lower slip as you do laps will allow you to find the sweet spot in which the trade-off between stability and control is found for you personally.

 


Engine and Parts Tuning


I am not certain that this was the intention when the developers at Turn 10 implemented the system, but the reality is that the Letter Number rating system that is used to determine the class of a car largely removed much of the need and effectiveness of tuning the engine and parts other than for power and stability (torque). You are going to find that your best results are to use the recommended settings and parts obtained through the auto-tune feature believe it or not.


You can still adjust these if you like, but do not be surprised when the part you want to use sends your car into a different class!


Conclusions


Your power profile in auto-tuning will bring you as close to the top end for horsepower as the game can manage without changing the class of the car, and 99% of the time the selections that it makes are the best for the class. Where you want to concentrate our attention is in the setup of the suspicion and tires, because stability and handling are largely what is going to win you the race.


Tuning in Forza 4 is less about making your car faster and more about making your car an extension of YOU. The more control you have, the better you will race, and you can only obtain that control by tailoring your car to your driving style and the track being raced.


This creates an onus on you, because in order to maintain that effectiveness you have to re-tune for each track, but once you know where your comfort levels are, that becomes less of an adventure and more of a science -- for you.


Remember, tuning in Forza 4 very little resembles the art of tuning a car in real life. In the game we are tuning to increase stability and our control, because these are critical to creating a car that we can control strategically in turns, because that is where all of the real action takes place in the game! No, that does not really reflect the sport in real life, but you work with what you have, right



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