Hey GroovierWolf3,
The essence to tuning the differential is actually more simple than you think, but that’s once you start to understand everything that’s going on at once, and as you said already, it’s complicated. But before we get to that, let’s first make sure you understand the component more in depth (as it’s essential to understanding how to tune it).
For starters, there are no springs in a clutchpack differential. And for all intents and purposes I would say that none of the race differentials in FM4 are Torsen differentials (I say this because the in-game telemetry allows us gamers to actually see the differential locking up); Torsen differentials are designed specifically for the purpose of NEVER locking up (Quaife established themselves with a very strong presence when they developed and released their Torsion based ATB differential).
I’ve posted it before, but here’s one of the links again of a guy explaining the three different types of differentials; 1 Way - 2 Way - 1.5 Way LSD - Explained - YouTube. The only reason I’ve posted this link is for the purpose of understanding what the pressure rings are and how they work; that is, that the pinion shaft is allowed to move either forward or backward to some degree. To what degree, however, is determined by whether the differential is a 1-way, 1.5-way, or 2-way.
That’s why I’ve tracked this photo down; http://www.billzilla.org/lsdoptions.jpg. Here you can effectively see the differences between the three types and the pressure rings they bear. The difference in the angle of the pressure rings is what allows the pinion shaft to travel more or less, thus applying more or less pressure to the clutchpacks. All of this is a byproduct of engineering via applying the laws of physics.
In the 1-way differential you can see that pressure is applied when you’re on the throttle, but not during deceleration; this is why you cannot adjust the deceleration setting on a 1-way differential.
In the 1.5-way differential pressure is again applied under acceleration, but unlike the 1-way there’s now a lesser, proportional amount applied under deceleration; this is why (if I’m not mistaken) your deceleration setting automatically adjusts itself to your acceleration setting–it’s maintaining that mathematical proportion.
In a 2-way differential, however, you have the same amount of pressure applied under both loads–acceleration and deceleration. This means that you have full control over both settings.
In regards to how to tune it, I’m going to apologize for length right now–explaining a differential is MUCH easier to do (and much faster) over a headset than in a forum.
First, which one to use? A 1-way is going to be good for drag, and possibly drift. It will cause the differential to lock under throttle–a good thing for drag and drift–but will not entirely lock under deceleration; for drag this is moot–you don’t need to decelerate–but for drifting, a differential that slips out of being locked under deceleration may be a bad thing for certain drifters (it depends on the style of drifting; some use this to temporarily regain control before inducing oversteer again, much like others use the clutch and handbrake to do the same).
A 1.5-way is typically good for circuit racing and can be used for drag (again, deceleration is entirely moot as long as it locks under acceleration), but often times is useless for drifting. Because of the design of a 1.5-way differential, it’ll usually provide more grip under deceleration because the differential hardly locks up; this is critical because the inside and outside tires must travel different distances, which means the outside tire must spin faster (like in that first Youtube video I posted for you). If the inside and outside tires MUST travel different distances, the differential must NOT be locked for optimal grip. If it is locked during cornering, your inside or outside tire will spin more or less than it is supposed to depending on which tire is locked to the other. If the inner tire is locked to the outer tire it will spin faster than it needs to for the turn, thus causing oversteer; if the outside tire is locked to the inside tire the outside will not spin as fast as it needs to for the turn, thus causing understeer and/or wheel skid/hop.
A 2-way is usually ideal for drifting, as you can effectively get the tires to lock under both acceleration and deceleration, but can also be effective for circuit tuning for those who know how to create balance between both loads. With a 2-way differential, you have total control over when your differential unlocks (corner entry) and locks (corner exit). If you think of tank treads, like I mentioned before, creating a certain ratio between between the inner and outer treads, or tires in your car’s case, will create a specific turning angle. If the angle produced by your control over your car doesn’t match the turning angle induced by the differential’s settings, your car will feel unstable until both angles become one again (or close enough to one). A 2-way differential is sort of unique in that it gives you control over both your corner entry angles and corner exit angles (to a certain degree–it will have its limitations in that it won’t turn the car for you), which is something neither a 1-way or 1.5-way can do. The downside to this, however, is that it can require intense amounts of time spent trying to find a perfect (or even suitable) balance between both acceleration and deceleration when using a 2-way on certain cars.
When you choose your differential, you’ll first have to decide what kind of control you want–just corner exit (in which case you’ll use a 1-way or 1.5-way) or both exit and entry (in which case you’ll want a 2-way). Also remember that a higher setting means more clutchpacks, and therefor more resistance to wheelspin and rotational speed differences between the inside and outside tires; this means that the higher your setting, the more the driving tires affected will want to drive in a straight line, and the lower the setting, the less it will want to drive in a straight line and the more inclined the car will be to turn.
When adjusting for corner exit (this is your acceleration setting; it only applies when you’re using the throttle), you want the differential to lock as you get the car to straighten out. This is harder than it sounds however, because the nature of a turn determines how quickly or slowly the diff needs to lock on corner exit (your throttle input as you apply it can affect how quick or slow it locks too). The broader a turn is (as in obtuse angles, i.e. large sweeping corners, etc.), the more time will be spent straightening the car out; therefore, the differential will have to lock more slowly. The tighter a turn is (as in acute angles, i.e. hairpins, etc.), the faster the differential will need to lock. Your settings will have to be a balance between what is required for the most obtuse turn angle and most acute angle of turn for the track you’re tuning for. In other words, the tightest turn in the track determines how “closed” your differential can be while the broadest turn in the track determines how “open” your differential can be. You don’t want your differential more closed or open than necessary.
When it is more open than necessary, the tires altogether will attempt to make turns sharper or faster than necessary. While this can be beneficial to slight degrees, too much will contribute to enough loss of grip to negatively impact your lap times. Beyond using the telemetry system to watch replays in slow motion, you can monitor for insufficient resistance (or too low of a setting) by watching for excessive wheelspin on the outer tires which may or may not cause the car to want to continue turning rather than straightening out (which sometimes can require a corner-exit steering over-correction). The effect of this, however, will vary between car class, drivetrain type, and wheelbase.
When it is more closed than necessary, the tires altogether will attempt to maintain more of a straight line rather than turning, resulting in turning responses that are either sluggish or turns that result in sharp and sudden losses of traction on the inside tire; it’ll depend on which tire is not spinning at the proper rotational speed. With excessive resistance (or too high of a setting) one of two things will happen; either the inside tire will spin too fast, or the outside tire won’t spin fast enough. When the inside tire spins too fast, the inside tire will lose grip usually in a very sudden manner causing the outer tire to usually lose grip very suddenly too (this is VERY common for RWD cars). When the outside tire doesn’t spin enough, on the other hand, it will slowly lose it’s grip and usually causes the inside tire to lose grip too, though the loss of grip is much more gradual (this can be very common for FWD cars).
It’s worth noting that I’ve had to, in many, many, many, many, many cases, run a car for a five lap race by myself just to save the replay and watch it back in slow motion so that I could actually see which tire was losing grip first and why. Don’t be too surprised or frustrated if you find yourself having to do the same.
When adjusting for corner entry (this is your deceleration setting; this only applies when decelerating while in gear), you want the differential to open up, or unlock, as you turn in towards the apex, presumably at the same rate at which you’re turning the car. This can be even trickier than setting your deceleration setting because your differential will change states as you downshift; each shift of the gears will render the car in neutral for a temporary amount of time which allows the pinion shaft to slightly move. This effect can be troublesome at times during trail braking if the settings aren’t optimal because the movement of the pinion shaft may allow for a change in the transfer of torque rendering the clutches in the clutch pack unresponsive.
When you have too low of a setting the differential will be allowed to unlock itself too soon, allowing the torque to differentiate itself on the inside and outside tires too early which can have a negative impact if you’re weight has started to transition at this point. Once the weight transitions to the outside, the inside tire has less weight on it to maintain grip, so if it’s delivered too much torque too soon, it can become unstable or maybe even lose it’s grip as you near the apex of your turn.
When you have a setting too high, however, the differential won’t open soon enough and will cause the car to deviate from your steering input at a rather steady rate. This will either be perceived as a gross amount of understeer, or can cause the car to snap loose. This is because the car will continue to want to drive in a straight line (this is your understeer, and occurs when grip is maintained), or will attempt to drive in a straight line until transitional weight allows the lighter tire to begin slipping (this is the “snap loose” effect, caused by the weight transitioning just enough that the tire can slip suddenly and push the other tire beyond its grip).
This is as far as I can go for now, but I’m willing to elaborate more if you would like me to or need me to. I hope that all of this helps, and again I apologize for the length.
Cheers!
