THE INSIDER’S GUIDE
The differential in a car allows the outer driven wheel to rotate faster than the inner driven wheel when a car is in a turn; adjusting the rates of the differential can have massive implications to how your can handles. In Project CARS 2, tuning your diff’ has enormous affects on your setup, and in this week’s Insider’s Guide, Yorkie065 will give you the down-low on how to adjust the diff for the various cars in-game
Before looking at the differential, and how it can be tuned for both speed and handling, the following should be noted:
― Both the location of the differential on the car, and which wheels do the power delivery, determine which section of the differential adjustment page is available to you. This is determined in the following way:
― Front Wheel Drive = Front Section
― Rear Wheel Drive = Rear Section
―Four Wheel Drive = Both Front and Rear Sections.
― Some cars also have access to the Centre section, as they have a diff in the centre.
― Only in the Centre Section can you adjust the ‘Rear Power Balance’ option.
― Only the settings that are tied to an ‘Enabled’ differential will have an effect on the car. For example, if a Clutch LSD is ‘Enabled’, then only the Preload, Number of Clutches, Ramp Angle Power, and Ramp Angle Coast will be in effect―all other options will not be applied to the car. If you want to apply another diff type, you will need to ‘Enable’ it for it to take effect, and for the adjustment of any options under that diff type to impact the car’s handling and the way that differential works.
This enables or disables a spool (otherwise known as a locked differential).
Setting this to ‘True’ will enable the use of a Spool which will ‘lock’ the differential and force the axles to spin at exactly the same speed. This helps to maximise traction when powering out of corners. The trade-off for this increased traction, however, is reduced turning ability, as one side of the car will need to scrub the tyre across the track to follow a different path.
Setting this to ‘False’ will disable the Spool, and keep the differential active, allowing the driven wheels to turn independently of each other.
Note: If the Spool is set to ‘True’, it will disable all other Differential options that are available on the car. Setting it to ‘False’ will allow the use and tuning of other Differential types.
This enables or disables a Geared Limited-Slip Differential. This is a torque-sensitive, mechanical differential which limits wheel-speed difference by biasing engine torque to the slower-spinning axle.
If one tyre loses traction and begins to slip, for instance, the Geared LSD will sense this, and send a larger proportion of torque to the non-slipping tyre where it can be used more effectively. This Geared LSD biases torque only when needed, and consequently has less of an effect on vehicle handling than a Clutch LSD or ratcheting locker.
BIAS RATIO, POWER
This controls torque distribution of the Geared LSD when on-throttle.
Adjusting the Power Bias Ratio changes the amount of on-throttle torque that can be delivered to the tyre that has better traction. For example, setting the Bias Ratio Power to a value of 3.0 will mean that the differential is capable of delivering up to 3.0 units of torque to the tyre with better traction for every 1.0 units going to the slipping tyre.
Using a higher value will increase the locking effect when wheel-slip is detected, and a lower value decreases locking. Find a value which is high enough to prevent power loss from wheelspin on corner exit, but not with excessive locking so as to cause power-on understeer, or snap oversteer when both tyres suddenly lose grip.
BIAS RATIO, COAST
This controls torque distribution of the Geared LSD when off-throttle.
Adjusting the Coast Bias Ratio changes how engine-braking torque is distributed between the tyres when off-throttle, as well as when slip is detected. This works in the same way as the Power Bias Ratio, where setting a ratio of 3.0 means the differential will send three times as much torque to the tyre spinning more slowly, but remains active when the throttle is closed, and the engine is outputting braking (negative) torque.
Higher values for Coast Bias Ratio will create a larger locking effect when off-throttle, increasing stability during turn-in, and corner entry. Too much locking in the coast phase, however, can lead to turn-in understeer. Lower values decrease the amount of coast-locking and can consequently allow for better turn-in, but can also potentially cause lift-off oversteer due to the lack of the stabilizing force.
This enables or disables a Salisbury-type Clutch Limited-Slip Differential.
This type of differential uses the same components as an open differential but adds a set of friction clutches to bind the two axle halves together. These clutches are activated by preload springs and cam-ramps which convert engine torque into a locking ‘moment’ across the differential.
This controls the amount of built-in lock applied to the differential clutches before any Power or Coast effects are added. As such, it will affect the balance of the car when cornering in a neutral throttle situation and will also affect the smoothness of the transition going from off-throttle to on-throttle.
Low settings here will improve manoeuvrability, whilst a higher setting will reduce it. As long as the torque differential doesn’t overcome the preload, the differential remains locked.
Balance the Preload in order to make it high enough to give stability during neutral-throttle cornering, but low enough not to create excessive understeer.
RAMP ANGLE, POWER
This adjusts differential locking of the Clutch LSD when on-throttle.
Lower ramp angles create more force on the clutch friction plates which then increase the locking effect. This can improve acceleration out of corners by preventing the inside tyre from spinning and sending power to the tyre with most grip instead. Too much locking effect can result in power-understeer in light-throttle situations by binding the axle too quickly.
Higher ramp angles reduce side force on the clutches with 90° giving no locking effect on power and which effectively disable this feature of the differential.
Use a power ramp angle to give enough locking effect so that excess wheelspin is prevented on corner exit. Bear in mind the engine power when setting this value: an engine with low power may want lower, more aggressive ramp angles, as there is less torque to turn into a locking effect from the start.
RAMP ANGLE, COAST
This adjusts differential locking of the Clutch LSD when off-throttle.
Lower ramp angles create more force on the clutch friction plates, thereby increasing the locking effect. This can help stabilize the car on corner entry by using engine braking to bind the axles together more tightly. Too much coast locking can lead to understeer during turn-in.
Higher ramp angles reduce side force on the clutches with 90° giving no locking effect on coast, and which effectively disable this feature of the differential.
NUMBER OF CLUTCHES
Changing the number of clutches adjusts overall strength of the Clutch LSD without altering the relative Power and Coast ramp angles. Adding clutches simply multiplies the locking effect from the differential ramps: a setup with 4 clutches, for instance, provides double the lock of a setup with 2 clutches.
Preload torque is not affected by the number of clutches.
This enables or disables a Viscous Limited-Slip Differential.
This type of differential uses the hydrodynamic friction of plates spinning in a highly viscous fluid to generate a locking effect between the axles. When the two sets of plates are rotating in unison, no viscous force is created. When the plates start rotating at different speeds, shear from the fluid creates a torque to resist this which is proportional to the amount of differential.
Viscous differentials are smooth as the locking is purely proportional to the amount of axle speed difference and not dependent on torque output from the engine. They cannot, however, prevent wheelspin before it has happened, as some slip is required to create the locking action, and the viscous friction of that action will consume some engine power.
This adjusts the amount of locking from the Viscous LSD. Units for this are locking torque per 50RPM of wheel-speed difference.
Higher viscous locking will add stability during turn-in, as well as traction on-power during corner exits. Too much, however, can cause too much resistance to chassis yaw which will create understeer, much like with a Spool. It can also cause excessive drag on the driveline by generating too much viscous friction when not all of it is needed to balance the car.
This allows the enabling or disabling of the Ratcheting Differential.
Setting this to ‘True’ will enable the Ratcheting Differential, which is a simple differential type that fully locks up on-power while remaining fully open when coasting. This maximizes traction on power, like a Spool, while keeping the car nimble during cornering, like an open differential. Drawbacks include the potential for notchy handling, as the transition from fully-locked to fully-open is abrupt and controlled only by your right foot.
REAR POWER BALANCE
The Rear Power Balance allows control of how much of the driven power is sent to the rear wheels in an all-wheel drive (4WD) car.
Increasing the Rear Power Balance will bias more of the engine power towards the rear wheels, making them do more work in delivering the power to the road surface while also increasing power oversteer. Decreasing the Rear Power Balance will put less power to the rear wheels and more on the front wheels, thereby increasing understeer on-throttle.
Consider the track type and weather conditions when setting the Rear Power Balance. A dry track with fast corners may benefit from more Rear Power Balance to aid with corner exit, as the fronts are already under hard loads from cornering. A wet track, or one with slower turns, may better suit more power being sent to the front in order to get better launches off corner exits.
Now sit back, relax, and let Yorkie065 take you through the inside workings of differentials in this week’s Insider’s Guide to Project CARS 2.