Forza Horizon 4 vehicle tuning is one of the main gameplay methods in the game. How to modify and tune the vehicle? Let me share with you a summary of the vehicle tuning principles of Forza Horizon 4
A summary of the vehicle tuning principles of Forza Horizon 4
Chapter 1 Engine
1 .Naturally aspirated and supercharged
Naturally aspirated is a form of forcing air into the combustion chamber through atmospheric pressure. As the cylinder piston moves downward, it draws in air so that fuel can be burned in the cylinder. Common turbocharging is a technology that uses exhaust gas generated by the operation of an internal combustion engine to drive an air compressor. From a structural point of view, the difference between turbocharging and self-priming is that there is an additional air compressor to increase the air intake volume by compressing air, so that the turbocharged engine can suck in more air with the same cylinder volume. cylinder and supports the combustion of more fuel, thereby increasing power. The principle is similar to supercharging, but the difference is that it directly drives the air compressor through the engine crankshaft.
For naturally aspirated engines, as the speed increases, the power and torque will increase in a relatively stable trend. Supercharging is similar in that an air compressor supplies compressed air to the engine as long as the crankshaft is moving. However, due to turbocharging, the exhaust gas cannot provide enough energy to drive the air compressor at low speeds, so the turbocharged engine performs poorly at low speeds and needs to maintain a certain speed to provide strong torque and power. Especially in off-road and rally races where acceleration and deceleration are frequent, special attention needs to be paid to shifting gears to ensure engine speed. Compared with turbocharging, supercharging will become a burden on the engine at high speeds because the mechanical structure is difficult to adapt to extremely high speeds.
2. Parts modification
The more important ones are the camshaft and turbine. The camshaft can increase the limit speed, so that the engine can provide more power at high speeds and shift gears more smoothly. The turbine purely increases horsepower and is modified when the horsepower is insufficient.
Unless the engine horsepower is too poor, modifications are basically made up of parts
Chapter 2 Clutch and Gearbox
1. Clutch
< p>The clutch affects the shifting speed. For rally and cross-country races with frequent gear changes and constant acceleration and deceleration, speeding up the gear changes will improve acceleration and deceleration performance.2. Gearbox
By adjusting the gear ratio of the transmission gear, the gearbox can output the power output from the engine crankshaft to the drive wheels in different combinations of torque and speed. Generally only the final drive ratio needs to be adjusted to achieve the desired balance between the vehicle's acceleration performance and top speed. If the gear ratios of each gear are uneven, they need to be adjusted separately. The final effect should be that when accelerating, the engine speed drops by basically the same amount for each gear up, in order to achieve the best torque output and the smoothest acceleration. For rally racing, if the top speed is not large, the gears can be reduced to minimize the time loss caused by upshifting and downshifting.
Modification of the transmission system is also done ~
Chapter 3 Car Body
1. Roll cage
Increase the strength of the car body , which is helpful for cross-country and rally races that take off at any time, and can improve the stability of the vehicle when it lands. However, it increases the weight of the vehicle and does not need to be installed on road vehicles.
2. Car body weight reduction
Reducing weight can greatly improve handling. After the car body is lightened, the inertia is reduced, and the acceleration and braking speeds will be accelerated. For curves, the centripetal force F=mv^2/r, that is, the square of the speed v is equal to Fr/m, that is, the larger the radius of the curve, the greater the limit speed; the greater the centripetal force, the greater the limit speed; the smaller the mass, The greater the limit speed. In the case of a level road surface, the source of centripetal force is friction. It is well known that the friction force f is proportional to the friction coefficient k and the positive pressure P. When the friction coefficient remains unchanged, the greater the pressure, the greater the friction force. That is, f=kP. There are two main sources of downforce for a vehicle, namely the gravity mg exerted on the vehicle and the downforce A brought by aerodynamic forces. At this time f=k(mg+A). Substituting into the formula, v^2=kgr+kA/m. When the air downforce A at high speed is not considered, mass has no effect on the corner speed limit. But in real situations, the lighter the mass, the better the cornering performance.
Some people always say that the weight of the car does not affect the steering performance. Let’s refute the rumor here
3. Aerodynamic kit
The main aerodynamic kit is the front lip and rear wing. They provide additional downforce to increase friction at high speeds, thereby improving cornering performance and stability. Taking the wing as an example, its lift is generally proportional to the square of the speed. Similarly, at low speeds, the aerodynamic kit will basically not work. It will only start to work when the speed increases and the air flow rate increases. Therefore, for low-speed corners, as well as off-road and rally races, aerodynamic kits will increase the weight of the vehicle and affect performance. For highway curves, it can be greatly improved. The increased pressure under the front lip will increase the friction of the front wheel and increase the lateral driving force of steering. The rear wing increases the downforce of the rear wheel, which can increase the transmission efficiency between the tire and the ground, and prevent the vehicle from oversteering and drifting when turning at high speed. (Oversteer, when the rear wheel slips, is called tail-drifting; understeer, when the front wheel slips, it is called head-steering) However, excessively increasing downforce will increase the rotational friction and resistance of the tires when the vehicle is driving, which will reduce the vehicle's ultimate speed. and increased fuel consumption and tire wear.
Chapter 4 Tires and Suspension
1. Tires
The higher the tire pressure, the greater the rigidity, and the tighter the connection between the wheel hub and the ground. If the tire pressure is high, steering and acceleration will respond quickly. However, the maximum friction force will be reduced and the tire will easily slip. Reducing the tire pressure will increase the contact area between the tire and the ground, make the tire softer, reduce responsiveness but increase friction. Rally racing cars generally have lower tire pressures than road racing cars. Similarly, increasing the diameter of the wheel hub and thinning the tire sidewall have the same effect as increasing tire pressure.
2. Tire positioning
The wheelbase is the width of the distance between the front/rear tires. The wheelbase is the distance between the front and rear axles. A wider wheelbase can improve stability during roll, such as sharp turns. However, when the wheelbase width is increased, the wheelbase is reduced in the same proportion. When the vehicle is pitching, that is, leaning forward and backward, the center of gravity moves forward and backward. The stability will become worse. The wheelbase generally cannot be changed. Vehicles with a long wheelbase have better linear stability, while vehicles with a short wheelbase are more flexible and stable in corners.
Kingpin caster angle is the angle of the steering axis. Just like the front wheel of a bicycle, the axis of rotation is at an angle to the ground when turning. When the kingpin caster angle is 0, the steering axis is perpendicular to the ground. If the tire is simplified into a circular plane, the intersection line between the tire plane and the ground plane, that is, the straight line in the direction of rolling friction, is completely consistent with the rotation of the steering axis. How many degrees the steering shaft rotates will change the tire rolling direction. And at this time, the pressure in the vertical direction of the vehicle does not affect the steering of the tires. Assuming the extreme case, the inclination angle is 90 degrees, that is, when the steering axis is parallel to the ground, it can be imagined that no matter how the steering axis rotates at this time, the intersection between the tire plane and the ground plane will be horizontal and forward, no steering will occur, and the height of the steering axis will change. Low. So the greater the inclination angle, the lower the steering sensitivity.
When the car is traveling in a straight line, if the steering wheel is accidentally deflected slightly by an external force (for example, deflected to the right as shown by the arrow in the picture), the driving direction of the car will deviate to the right. At this time, due to the centrifugal force of the car itself, at the contact point b between the wheel and the road, the road surface acts on the wheel with this lateral reaction force Fy. The reaction force Fy forms a moment FyL acting on the wheel around the kingpin axis, and its direction is exactly opposite to the wheel deflection direction. Under the action of this torque, the wheels will return to their original middle position, thereby ensuring that the car runs stably in a straight line, so this torque is called a stabilizing torque. Helps stabilize the vehicle on bumpy roads.
Toe angle refers to the angle formed by the tire and the central axis of the vehicle when we look at the vehicle from directly above.
If Toe out is set, the steering will be sensitive when entering a corner; if Toe out is set to a too large angle, there will be a tendency to oversteer; if it is set to Toe in, the steering will be slow ;Set too large Toe in, and the vehicle will deflect to understeer.
The Ackermann angle is designed to prevent the vehicle from slipping when turning. When designing the steering mechanism, the turning angle of the inside wheel (relative to the bending center) is slightly larger than that of the outside wheel. Make the angle of the two wheels larger and smaller to form an included angle, thus forming the Ackermann angle. This design allows the steering wheel to keep the rolling direction consistent with the actual displacement direction when the vehicle is cornering quickly, maintaining a more stable grip. Therefore, the toe angle of the splayed tires is stable for steering but unstable for straight driving. For the vehicle's rear wheels, most tracks are set to inside eight. Because when the vehicle turns, the weight of the vehicle body will press on the outside tires of the vehicle. If the outer eight setting is used at this time, the wheels will point to the outside of the vehicle, which will pull the rear of the vehicle outward, which will bias the drift and tail characteristics. instability.
Tire inclination is the angle formed between the wheel and the vertical line on the ground when looking from the front of the car.
When the car is cornering, the body will tilt to the outside. At this time, our wheels will also tilt to the outside. Assuming that the camber angles of all four wheels of our vehicle are 0, then in a curve, if our outer tire is hard on the outside, only the outer side will be in contact with the ground due to the inclination, thereby reducing the contact area with the ground and reducing the grip. Then when we set the camber angle to a negative number, the outer wheel of the vehicle will be in contact with the ground in the maximum area in the curve, thereby obtaining better corner grip.
When adjusting the inclination angle, you can rely on the tire temperature to judge. When the tire temperature on the inside and outside of the outside tire is basically the same during continuous steering, it means that the contact between the tire and the ground is the most complete at this time, the contact area is largest, and the grip performance is the best.
3. Spring and damping
Wheel track adjustment is equivalent to improving the overall geometric balance of the car, and overall improving the handling of the car in terms of grip and load. Adjusting the wheel posture is equivalent to improving the control on the grip track. Suspension tuning will improve load transfer on all four tires for handling.
Load transfer is the transfer of center of gravity and weight. Just like physical inertia, when the car brakes, the car will tilt forward due to its own weight. Most of the load is applied to the front wheels. This is load transfer. . When accelerating, the load is concentrated on the rear wheels; when turning, it is the front and rear outer wheels (the front outer wheels bear a greater load than the rear outer wheels). Because of the uneven road surface and the effect of the suspension, there is load transfer, which causes the grip of the four wheels to constantly change. F1 uses a low center of gravity, lightweight body and a mid-mounted engine that distributes weight more appropriately in order to minimize load transfer.
The function of the suspension is to make the load transfer less violent and not overly sensitive.
So the softer the suspension properties, the more balanced the load transfer. When driving, the car's load transfer can be accurately controlled to obtain maximum four-wheel grip. But on the other hand, suspension that is too soft will cause the car to roll too much and lose control sensitivity and tracking. The harder the suspension attributes, the more precise and sensitive the control and tracking will be, but the load transfer will also become more intense, reducing the fault tolerance, ultimate grip and adaptability to the road.
Spring is the basis of suspension. It will generate a rebound force with compression. The longer the compression length, the greater the rebound force. Therefore, the car will press the spring to a certain level, and the elastic force of the spring will gradually increase until it is equal to the pressure given by the car, maintaining a certain height and supporting the body. The flatter the spring is, the more elastic force it will give.
Damping is a component that constrains and controls the spring. It is different from the spring. It is installed next to the spring and will only continue to provide resistance to the spring's compression or rebound, making the spring more gentle when compressed and rebounding. The bounce is not so violent that the car will not jump around. The cooperation of springs and dampers allows the weight of the front and rear tires to be well shared when the car's load is transferred. For example, when the car accelerates, the rear wheels compress and the load is slowly transferred to the rear wheels, but the front wheels do not tilt directly. Instead, as the rear wheel spring slowly compresses and stretches, it helps the car transfer load rearward without losing grip of the front wheel quickly. Specifically when decelerating into a corner, assuming that the rebound damping of the rear wheel is high, the load is transferred to the front wheel during braking, and the rear wheel pressure is reduced and the spring is stretched. However, due to the presence of rebound damping, the spring cannot be stretched quickly, and the tire It will leave the ground, and the rear wheel will lose grip and cause the tail to drift; similarly, if the compression damping of the front suspension is reduced at this time, the front suspension will quickly compress, the front of the car will sink faster, and the rear of the car will rise faster. It will also reduce the rear wheel grip and cause tail drift.
The function of the anti-roll bar is to tighten the suspension on both sides. It will inhibit the movement of the suspension on both sides in different directions. For example, when turning, the inner suspension is stretched and the outer suspension is compressed. The anti-roll bar will tighten the body to prevent the body from rolling too much.
The anti-roll bar can be adjusted to be soft or hard. The stiffer the anti-roll bar, the stronger the connection between the suspension and the body, but it may cause the inside wheel to lift off the ground during sharp turns, and the total grip on the inside and outside will become smaller. A softer anti-roll bar will cause the body to roll while the tires maintain grip. The ultimate situation is that there is no load transfer at all on the inside and outside tires when turning, and they still maintain the same pressure on the ground. Therefore, the front and rear suspension anti-roll bars can adjust the grip of the front and rear inner and outer tires respectively to achieve the effect of adjusting the total grip of the front and rear sides, thereby adjusting oversteer and understeer.
In summary, the car needs to sacrifice some load transfer to maintain flexibility when there are tight corners. On the one hand, it is the adjustment of tire positioning, on the other hand, it is the anti-roll bar and suspension rebound. Each of these parameters has its own division of labor:
Toe angle affects the trajectory during steering and continuously affects the attitude of the front and rear wheels; rebound affects the initial load transfer, and anti-roll bars affect the inside and outside of the bend. Balance of grip. In addition, stiffer springs and compression damping can also make the load transfer process from straight lines to corners more flexible;
The details of grip are composed of tires and inclination angles. The wider the tire, the better the cornering and the lower the tracking performance. The tire pressure will make the skidding process silky (soft) or simply (hard); the inclination angle controls the best grip area, so you need to observe the wheel. And the fit state of the track; Ackerman angle and caster angle will affect the performance of wheel steering. The Ackermann angle affects the direction of the inner wheel, and the kingpin caster angle affects the support of the steering wheel.
The wheelbase will affect the entire vehicle's posture, including load transfer, wheel direction and vehicle body movement.
In short, adjustment must comprehensively observe the movement of all components, and make the body posture more coordinated through the cooperation of various parts, so that the car can match the track and the driver, and ultimately achieve perfection through clear-cut movement changes. dynamic balance.
Chapter 4 Transmission System
1. Limited-slip differential
When turning, there is a speed difference between the inner and outer tires. Due to the weight transfer, the downforce of the inside tire is small and the downforce on the outside is large, that is, the grip on the outside is greater than that on the inside, and the resistance to tire rotation is also greater on the outside than on the inside. When the drive shaft is outputting power, if the power is too large, the inner wheel will slip first and lose its grip. While slipping, its resistance will be further reduced, and the drive shaft will output all the power to the slipping tire, causing the wheel that really grips the road to The outside tire loses power. Overall, the reduced driving force of the outside tires of the car will lead to insufficient steering force and understeer. So a limited slip differential needs to be added. Structurally speaking, several friction plates are added to the differential so that the left and right axles can be connected to a certain extent. The higher the locking rate of the limited-slip differential, the closer the inner and outer tires are connected. When it reaches 100%, it is equivalent to no differential, and the inner and outer tires rotate at the same speed. At this time, oversteer and slippage are serious. Limited-slip differentials are divided into acceleration differentials and reduction differentials. The former controls the degree of locking of the inner and outer tires when the accelerator is stepped on to accelerate, and the latter controls the degree of locking of the inner and outer tires when the accelerator is released and the engine is braking. The principle of the deceleration differential is similar. During deceleration, the brake oil pressure, that is, the braking resistance, received by the inner and outer tires is the same, while the outer tires receive greater ground friction.
Assuming that the locking rate is 100%, the pressure between the outside tire and the ground is large and no sliding occurs, and its stroke is greater than the actual stroke of the inside tire. If the inside tire is completely locked with the outside tire, the rotational stroke of the inside tire is greater than the actual stroke and sliding occurs. , losing grip. When the vehicle as a whole decelerates into a corner, the main turning moment comes from the braking friction of the inside tire (you can imagine that if the left tire brakes only, the vehicle will turn to the left), so the higher the lock-up rate, the more likely it is to understeer.
2. Driving wheels
Firstly, according to the position of the driving wheels, they are divided into front-wheel drive (FWD) (Front-Wheel Drive), rear-wheel drive (RWD) (Rear-Wheel Drive) and four-wheel drive (4WD). Four-Wheel Drive) or AWD (All-Wheel Drive).
The characteristic of FWD is that the engine installed in the front transmits power directly to the front wheels, improving traction efficiency, and 60% to 70% of the weight is concentrated on the front of the car, providing better stability , but the front wheels have to withstand 75% of the braking force, and the body's center of gravity shifts backward during rapid acceleration, which will cause acceleration delays and understeer in terms of control. Because the center of the drive shaft is too close to the center of gravity of the vehicle, it is difficult to provide sufficient steering torque.
RWD is characterized by sensitive steering, but it is difficult to maintain a stable attitude when the rear wheel slips due to oversteer because the front wheel does not provide power. And it is very easy for the rear wheels to slip when starting a high-horsepower rear-wheel drive vehicle. The starting performance is poor and an additional traction control system is needed to prevent excessive traction. However, due to its simple structure, high transmission efficiency and higher top speed.
AWD has the best handling, and because the traction force is distributed more evenly, all traction force can be completely transmitted to the ground. And since the front wheels also have driving force when turning, the steering stability is better. AWD models are equipped with a center differential that can independently adjust the power distribution to the front and rear wheels. The more power distributed to the rear wheels, the more RWD will be biased, which will increase oversteer.
Intuitively look at the tire downforce, taking the Volkswagen IDR as an example
This is the tire pressure in the parking state, the size of the green circle represents the amount of downforce
Next are the tire conditions at 50km/h, 110km/h and 230km/h. It can be clearly seen that the green circle begins to become slightly larger at 110km/h, and the downforce becomes larger, while the downforce is not significant at lower speeds. Increase, only at high speeds will there be strong downforce
Additionally, tire pressure and sidewall thickness can be understood in terms of shoes, just like football shoes and basketball shoes. The soles of football shoes are very hard. But it feels very comfortable to run, especially on the relatively hard plastic track of the playground, which feels very grippy. The basketball shoes are air-cushioned and have a very comfortable bounce, but they feel bouncy when running, which is not so fierce< /p>
Brake
When ABS is turned on, there is basically no need to make major changes. The introduction text next to the tuning interface makes it very clear, because the braking action before entering a corner is very simple and only involves the front and rear wheels. load distribution, and the resulting change in grip. Keyboard players can lower the oil pressure, while players with linear control handles can increase it appropriately. If ABS is turned off, it needs to be judged according to personal feel.
The so-called understeer and oversteer, I personally think we need to distinguish whether it is a posture problem or a loss of control problem. If it is an attitude problem, then the car is still in a controllable state, because the steering system will automatically adjust the direction of the front wheels as the speed changes. In other words, even if the steering is stopped when understeer occurs, the front wheels will not lose grip. , the car rushes straight forward, and when it is not out of control, it oversteers and does not directly drift out of control. Instead, the steering is too sensitive and rushes toward the center of the bend. If the speed is increased to increase the turning radius, it may lose sideways. Grip, this is when the tail flicks out of control.
To sum up, what can be adjusted in tuning is more about the body posture, so that the maximum speed of the car can just match the maximum steering ability when cornering. The most control is achieved by adjusting the tire inclination and suspension height. The simplest is the lateral g force, which actually affects the maximum speed of the bending center. Adjusting it is more enhanced by modifications such as tire tread and body weight reduction. Tuning is just the icing on the cake.
An important factor in whether you lose control or not is the various auxiliary settings. Unless your skills are very good and you have a deep understanding of the characteristics of the car, it is recommended that you turn on ABS for rear-wheel drive cars. Traction control, having these really makes a difference
For example, Fortune Island has an ATV race.
The basic weight of ATVs after modification varies from 700 to 900kg, and some even weigh more than 600. With this weight, it is easy to lose control when lightly touching obstacles in cross-country races. It was rainy at night on that map, and the ground was extremely slippery. At this time, unless you are lucky and don't hit the stone wall, it will be really difficult to run. Turning on the stability control system will make everything different. It is easy to save the beach bike after drifting.