1. Janos Magasrevy
  2. Guides, Setups, Telemetry
  3. Wednesday, 25 November 2015

The following guide describes how the differential works for most F1 mods available in rFactor 2.


Differential Pump

F1 differentials are of a limited slip-type. This means the level of coupling between the differential input shaft and the rear wheel driveshafts is variable. The differential's level of coupling (or pump as it's shown in rFactor 2) determines how the torque is applied to both drive wheels in relation to one another. At 100%, both drive shafts are effectively locked together, and torque is always applied from the differential to both wheels equally. At 0%, if one wheel should lose traction unequal to the opposite wheel (as if half the car goes onto the grass shoulder), then the differential shifts or "slips" torque away from the wheel with the least amount of traction.



Understand, as this is a mechanical process the differential cannot operate giving great shifts of torque from one wheel or the other. In other words, regardless of the differential-lock setting, both drive wheels will always be getting a great amount of torque in an F1 car. Using a 0% differential pump setting, the shift of torque from the offending wheel is still a minor percentage.



rFactor 2 allows us to fine tune the differential under acceleration and also off the throttle; these adjustments are called power and coast.


[b]Differential Power[/b]


The differential transfers more torque towards the wheel it thinks is the external one during acceleration. Keep in mind that the effect of the differential power only comes into action during corner exit and most importantly, during acceleration. Ideally, it would be tuned so that during acceleration, the exterior wheel pushes more forcing the car to continue on the track without incurring in a spin. If during corner exits while under acceleration the car goes to the outside of the track, you should lower the differential power setting. On the other hand, if the car starts going towards the inside of the curve under acceleration, then you should increase the differential power setting.


[b]Differential Coast[/b]


The differential transfers more torque towards the wheel it thinks is the internal one off the throttle. The differential coast only comes into effect when off the throttle and mostly during corner entry. Ideally, it would be tuned so that when you lift the throttle the car's initial response is to enter the corner in a stable way, not too much to the inside and not too much to the outside. If under turn entry the car goes too much to the inside, then you should increase the differential coast setting. On the other hand, if the car goes too much to the outside, you should decrease the differential coast setting.


Preload

The preload affects how smooth the transition from power to coast occurs. We can think of it like the "differential reflexes". Higher preload values require more torque before the differential shifts from power to coast. On the other hand, if the preload is configure low, then less torque is required before the differential shifts from power to coast. This is usually the last modification done to the differential, you would use it to make the final adjustments. It is recommended to start from a very low setting and work your way up until you feel both the differential power and coast are acting at the ideal time.


Summary




[b]Differential Component[/b]



[b]Adjustment[/b]



[b]Result[/b]





[b]Pump[/b]



High values (>50%)


Both rear wheels would have nearly the same amount of torque as it approaches 100%. Useful at circuits with long straights and few slow corners.




Low values (50%)


Forces the car to go towards the outside of the corner during corner exit under acceleration.




Low values (50%)


Forces the car to go towards the outside of the corner under braking or coasting off-throttle.




Low values (
Janos Magasrevy
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How does this information actually translate to any game MOD, such as rFactor2?

Example: No amount of input from the individual foot on the throttle at 100% PUMP will result in one rear wheel accelerating faster than the other rear wheel.
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I don't quite understand your question Joe.

From what I've read, 100% pump gives the same amount of torque to both wheels, so there will not be a wheel spinning faster than the other.

Maybe our resident mechanic, Cory Mackey, can give us some input on this.
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I don't know about the MOD used here this coming season, but I had trouble with the inside rear wheel getting hot and wearing out fast under acceleration using last years MOD in the FiHS League. If the game differential works the way the information above reports, then I should have been able to completely remove the inside tire heating up by locking up the two rear tires as if both rear tires were on the same solid shaft driven the same speed by the engine; and to do that I would increase PUMP up to 100%.

Like this:

Problem: Exiting turns under acceleration causes excessive heat and wear to the lighter loaded (inside) rear tire.

Solution: Increase PUMP in the differential so as to force the outside and inside rear tires to turn at the same speed even when one tire is lightly loaded and therefore encountering less traction compared to the heavily loaded outside tire.

Does that actually work that way in the game, or is that a real world cause and effect that does not simulate well in the game?
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That is correct Joe. Now, this is just the theory, some mods don't adhere to it very well I've noticed.
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I don't know if this is the place to discuss current differential setup work for the new Mod, but I think it is important to find out what actually happens when changing these settings.

I put all settings down to the minimum, with the exception of wings which I put half way from minimum to maximum setting for both front and back, and then I went 10 laps with 100 Pump, back to 10 laps with 0 Pump, back to 10 Laps with 100 Pump.

I am faster with 0 Pump.

100 Pump forces me to turn the steering wheel a lot to get the car to turn-in, more so than 0 Pump.

Both 0 and 100 Pump are about the same (as far as I can tell) when exiting the turn with very slow and steady increase of the throttle to avoid snap oversteer. I did not want to add more rear wing and reduce front wing to stop the snap oversteer. I want to know the effect of changing Pump.

Rear tires wear more rapidly with 0 Pump and rear tires wear less rapidly with 100 Pump, and front tire wore about the same amount.

I am not confident in test results being useful since one thing only is changed, but the more laps I go around the track with the new Mod the less will the new Mod be new.

Next test round will be changing Power on the Differential with Pump remaining at 0. Then if I get an idea as to what Power does, I can try combining Pump and Power.
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Have you tried adding 50% pump to your tests as well? try adding a mid-range value to them, both extremes only doesn't give a clear picture.
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With all differential settings at minimum I found that the car finally rotates on turn-in, which is power off oversteer, or coast oversteer, depending upon how you look at it. If the car is in mid turn and the throttle is already feathered open, where the engine is driving the car (not coasting), then said power tends to lighten the front end, taking away traction from the front end, and adding traction to the rear end. Call it whatever you want: I like the ability to steer with the throttle when lifting the throttle, as lifting the throttle causes the rear end to step out, and the front end to point into the turn.

21 Laps on the first set of Medium tires, starting with a full load of fuel, and the left front was worn down to 22% on the Track Map Plugin HUD. At 22% (in the previous mod) that tire would be absent any grip at all, and with this Mod the tire is still offering grip; at a reduced amount. 22 Front wing, and 55 rear wing.

148.4 Liters left in the tank after 21 Laps (Malaysia) so...

220 - 148.4 = 71.6 Liters consumed in 21 Laps = 3.409 Liters per Lap Fuel Consumption Rate (corresponding with the Track Map Plugin HUD for Fuel Consumption)

56 Laps needed for the Malaysian GP so 56 times 3.4 = 190.4 Liters needed at that Fuel Consumption Rate for that limited test.

With Medium tires it looks like a 2 stop race so far.
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I missed your reply Janos.

Any of those Differential settings in my testing took away from my ability to coast oversteer, so those settings will remain at minimum for me until I find reason to increase one of them. The same goes for Brake Mapping: minimum gives me my coast oversteer, and any increase from minimum begins to remove that ability to turn the car by lifting the throttle.
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