1-Way vs 1.5-Way Rear Differentials
Jan 21, 2019, 12:34 PM
#121
bumping this - i've got the OSG in the car, but as soon as I did the weather turned to **** and I haven't been out yet. I disconnected the rear trailing arm when I simultaneously swapped the rear sway bars, and I need an alignment before I do any real driving. I've been thinking about this topic and had one question
obviously 1.5 ways lock on accel and partially lock on decel - I've been hypothesizing that this is the reason for my corner entry understeer - but, depending on driving style, if you're not decelerating much by the time you enter a corner/if you're even briefly coasting, doesn't that mean the diff is not locking at all, forwards or reverse? basically, coast = not accelerating or decelerating with any significant amount of force, then no lock?
obviously 1.5 ways lock on accel and partially lock on decel - I've been hypothesizing that this is the reason for my corner entry understeer - but, depending on driving style, if you're not decelerating much by the time you enter a corner/if you're even briefly coasting, doesn't that mean the diff is not locking at all, forwards or reverse? basically, coast = not accelerating or decelerating with any significant amount of force, then no lock?
Based on my understanding, engine braking will lock the diff (50% for the 1.5). However, I do not believe the diff is locked under normal driving acceleration or deceleration. This probably depends on each design, the ramp angles and pre-load springs, etc. but significant torque (accel or decel) generally needs to be applied in order to lock the diff.
I also have a new LSD waiting to be tested out, pending install. (MFactory Helical Front)
Jan 21, 2019, 12:40 PM
#122
but, as with acceleration, the amount of lockup force depends on how much force is going through the diff - i have to assume that relatively speaking, during minor coasting/braking, this is going to be a small amount of force acting on the diff - it's not on or off, so the percentage lock up so to speak is minor then?
Jan 21, 2019, 01:09 PM
#123
but, as with acceleration, the amount of lockup force depends on how much force is going through the diff - i have to assume that relatively speaking, during minor coasting/braking, this is going to be a small amount of force acting on the diff - it's not on or off, so the percentage lock up so to speak is minor then?
That's where the slip comes in, you can be engaged (locked) and slipping.
Perfect thought experiment would be driving a round-about, 3 circles.
1st you're on maintenance throttle, no lockup.
2nd you increase throttle/brake just enough to lock the diff, but the wheels are still spinning different speeds and with more grip than the LSD has to hold them locked together, so the LSD slips.
3rd, you increase the force on the LSD (accel or decel) to the point that you've overpowered or locked up one wheel, it spins/locks, which changes the RPM of the wheel relative to the other side. As this relative change occurs, the LSD differentiates which side the force is applied, limiting the slip between the two, resulting in a full lock (or in the 1.5 decel case, 50% lock).
In other words, you shouldn't notice the engagement unless medium-hard on throttle or near limit braking. All regular driving is just slip slip slip.
Jan 21, 2019, 01:15 PM
#125
Jan 21, 2019, 01:33 PM
#127
Also the inside rear being unloaded needed to be taken into consideration. How much effect can it have when its not on the ground
. But of course long before its off the ground, its barely able to do any work.
Jan 21, 2019, 03:25 PM
#128
EvoM Guru
iTrader: (1)
but, as with acceleration, the amount of lockup force depends on how much force is going through the diff - i have to assume that relatively speaking, during minor coasting/braking, this is going to be a small amount of force acting on the diff - it's not on or off, so the percentage lock up so to speak is minor then?
Jan 21, 2019, 03:29 PM
#129
Coasting is not the same as decelerating. Engine braking is the biggest factor in making the diff lock on decel. no throttle, no brakes, and in gear does not mean coast, that is decel for the diff, and that is when it will be most locked up. What makes the diff lock is the force inputted by the dirveshaft.
Jan 21, 2019, 04:08 PM
#130
EvoM Guru
iTrader: (1)
interesting, i did not realize this. Then how would, for example the OSG, "know" when to open up the lockup? If you assume a typical corner entry goes from hard brakes to soft brakes to a brief coast and then quickly back to squeezing on the throttle, i assumed that the hard braking/slow down forces the rear lockup to be the most aggressive - the wheels are slowed which forces the engine to be slowed, which forces the diff to be locked. you're saying that under hard braking and no braking/coasting, there is virtually no difference in a 1.5 way's lock up characteristic?
Jan 21, 2019, 04:45 PM
#132
EvoM Guru
iTrader: (1)
If you read and understand what I'm saying, it literally doesn't do that. Diff lock up is determined by the net torque input from the driveshaft, period. That's it.
Jan 21, 2019, 04:57 PM
#133
Our units are a negative preload design which allows for minimal lock when power is not delivered (turn in) and progressive maximum lock 100% on corner exit. Our unit is capable of controlling when 100% lock happens dependant on estimated power delivery and grip available (tires).
but you are saying there is no/little difference between when power is not delivered & when you are on the brakes correct?
Last edited by kyoo; Jan 21, 2019 at 05:02 PM.
Jan 21, 2019, 05:29 PM
#134
EvoM Guru
iTrader: (1)
That statement is dependent on ramp angles, ie whether it is a 1 way, 1.1 way, 1.5 way, or 2 way diff.