LSD differential parameter lsdRevLockCoef is working ?

I tried to use a LSD differential with a lsdRevLockCoef parameter without success. The goal was to create a 1 way or 1.5 way LSD differential.

This parameter does not seem to have an effect.

I have used an offroad car to test it, in low range, and watching the response of the rear LSD differential in forward then in reverse motion. I did disable the front shaft to better see the rear wheel motions.

When lsdRevLockCoef parameter is set to a very different value than lsdLockCoef, we should see an effect when comparing the differential in a forward move then in a reverse move.

What i can see is that the LSD differential behaves exactly the same in forward and reverse car motion. This is not the comportement we should have.

For example if i set 0.4 for lsdLockCoef, and 0 for lsdRevLockCoef, then i should get a one way LSD, locking only in forward motion acceleration. But what i can see is that it locks with the same cross torque in reverse motion. It is like if the lsdRevLockCoef would always take the default value of lsdLockCoef.

Then i suspect that there could be one of those three bugs :

- there is a typo inside the lsdRevLockCoef parameter name.
- there is a problem in the code for the LSD mode differential.
- the lsdRevLockCoef parameter is not implemented.

Could someone test it and confirm ?

 

Works as intended on vanilla K series.

 

Thanks a lot. Very interesting.

Then different cars could have a different internal computing engine for differentials ? That could explain that in my case it is not working ?

I'm using the slotType "pickup_differential_SFA" and "pickup_differential_R" on a Lancruiser 80 Series car.
--- Post updated ---
I did your test to see more easily the forward and reverse comportment.

I was able to get the lsdRevLockCoef working one time. But not more. It seems that it is not working anymore after changing the differential settings in tuning.

I'm going to try an application restart and a couple other things.
--- Post updated ---
Testing with the central diff, using a customizable LSD, i can see two interesting things :

- If lsdLockCoef is higher than a value that seems to be 0.35 (TBR = 2:1), then lsdLockRevCoef is not woking anymore. We got a 2 way LSD with equal Power and Coast TBR values, regardless the value of lsdLockRevCoef.

- lsdLockCoef and lsdRevLockCoef are reversed. This mean that lsdLockCoef is used for moves in reverse, and lsdRevLockCoef for moves in forward.

I did check, it is not reversed in my code between the variables and the differential definition.

I'm testing like this, locking the rear shaft, locking front and rear diffs, and using a customizable LSD diff for the center diff.




Back to testing for rear and front diffs.
--- Post updated ---
For the rear diff (i did not test but i suppose that it will be the same for the front diff) :

- Both Lock coefficients are not reversed like for the center diff.

- If lsdRevLockCoef is higher than lsdLockCoef, then lsdLockCoef is used for both coeff.

Same as for the center LSD diff, if lsdLockCoef is higher than about 0.35, then lsdRevLockCoef is not taken into consideration.

This mean for example that it is not possible to have a one way LSD with a 3:1 TBR. (3:1 = 0.5 torque addition). torque addition = (TBR - 1) / (TBR + 1)

Please could you test again with a 0.5 value for lsdLockCoef, and 0 for lsdRevLockCoef, and see if you still have a correct behavior ?

 

To summarize, according to what i'm seeing :

There is probably a couple problems in the LSD differential code :

- If the Reverse Cross Torque (lsdLockRevCoef) is set higher than Forward Cross Torque (lsdLockCoef), then the value of Reverse Cross Torque will become the value of Forward Cross Torque. This mean that it is not possible to have a One Way or 1.5 Way differential with locking in Forward motion deceleration or (Reverse Motion acceleration). This cannot be corrected by user code, but is not so important because in most situations we'll want more TBR for Forward acceleration moves.

- If Forward Cross Torque is higher than something near 0.35 (TBR is more than 2:1), then Reverse Cross Torque coefficient will become the same as Forward Cross Torque coefficient regardless its set value. This mean that it is not possible to have a 1 Way or 1.5 Way differential with more than 2:1 TBR (Torque Bias Ratio). This cannot be corrected in user code.

- for center diffs used on a transfercase, Forward Cross Torque (lsdLockCoef) and Reverse Cross Torque (lsdLockRevCoef) coefficients are reversed. This can be eventually corrected in user code.

Those three combined problems have made my initial diagnostic wrong when i said that lsdRevLockCoef had no effect at all.
It has an effect, but sometimes reversed for a center diff, and sometimes not working depending about the values of lsdLockCoef.

The second problem cannot be solved by user code and is a serious one : If Forward Cross Torque is higher than something near 0.35 (TBR is more than 2:1), then Reverse Cross Torque coefficient will become the same as Forward Cross Torque coefficient regardless its set value. Then we got a forced Two Way differential instead of the One Way or 1.5 Way we would want.