I spoke to UP about this, they are a big fan of the rear lsd as a way to prevent the ediff to kick on. They don’t actually mess with the electronics, they just give the car more mechanical grip to prevent the tc to come on
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LSD (limited slip differential) anyone?
- Thread starter TwoK4drSi
- Start date
Clivew
Member
ACD uses 1 pump for both ACD and AYC.
AYC uses way more than 2 gears. It has organic clutch plates in 2 packs for left and right distribution, 3 concentric helical gear clusters with 2 additional centre helical gears, and it can distribute torque to left and right wheels. The later SAYC also uses a torque multiplier to increase the torque transfer capacity. This info isn't from Google BTW, I've been rebuilding these diffs along with many, many others for 15 years.
You have more knowledge about diffs than I ever will have of any subject in life.
I rebuilt only 1 - mine. Evo X AYC drives right wheel only, but either speeds it up or slows it down which effectively works as distribution both sides. Anyway, it's completely off topic - Model 3 has simple open diff and you actually can feel that. So if UPP didn't notice any interference, you go usually on a track, not afraid to buy a new drive unit from your pocket and have a shop that dealt a lot with differentials - should be recommended option.
I think we're in danger of getting too bogged down in the technicalities of one diff vs. another. The ATB is a relatively low cost drop-in replacement which won't have any adverse affect on daily driving but should provide more mechanical grip when the car is driven hard. I had one on my last ICE car and although I'm not trying to compare that situation with this, I was happy with how it worked and the benefits I got from it, so I'm willing to give it a try in my P3D as an experiment.
Already decided I'm doing the rear initially and run it for a while before deciding if I want to do the front as well.
Clivew
Member
Sorry for off topic everyone, but this is just not correct, and if you think that then you obviously had your eyes shut when you built your diff. The diff drives both sides equally via either a bog standard open diff (exactly as per Tesla Model 3) on the earlier Evo 4-7 or via a torque multiplier on the later E8-10. Both sides driven directly by a driveshaft attached to both sides of the diff, same as Tesla, 50/50 torque distribution. It then uses clutch packs and gears (12 of them) to bias torque either left or right side, relative to the right hand wheel.
Clivew
Member
Already decided I'm doing the rear initially and run it for a while before deciding if I want to do the front as well.
Hopefully we can meet up at a trackday and have a back to back comparison once done.
Have you taken yours around Bedford yet?Hopefully we can meet up at a trackday and have a back to back comparison once done.
Clivew
Member
No, not yet. I’ve just fitted all the MPP arms last week, and am now on hols in the UK visiting parents for first time in 8 months.
So, next stage is sorting the brakes, so looking at making my own bells/brackets and using an AP caliper, or buying an off the shelf solution like MPP stoptech, depending on my time and workload. I push cars very hard on track, so need brakes solution first, otherwise I will damage the standard set-up.
ElectricGhost
Member
I disagree with #2. It’s actually less safe unless you know how to drive with one. Especially on the street because you rarely use it enough to get used to it. I put one on my bmw 335 that was tuned. It gave me sooo oversteer. I almost put it into a wall on the inside of a turn as that was more oversteer than I had ever experienced and it was completely unexpected. If it was safer you would see it a lot more on OEMs.
lol, it's simply an excuse to tell the wife so you can buy it. Chances are she wouldn't know the intricacies of how LSD works and if she actually does know, you won't even have to make up an excuse.
On a serious note, putting LSD on a Tesla would be quite different than LSD on a tuned 335. The Tesla's traction control is much better at managing traction.
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I had an ATB on a 335 also. Even in sport+ mode you'd have to be driving pretty recklessly to put it into a wall. There's no point modifying any car with something like a LSD if your skill level isn't up to it.
Agree on all counts. Surprised this hasn't come up, but I'll bring it up. The biggest advantage of a plate diff is under braking. A torque biasing diff will not keep the wheels turning the same speed under braking. As I moved through the groups and got faster, my first experience with non-open diffs was under acceleration, no longer spinning the inside wheel. Not a super fast car, a stock 944 Turbo S. But I never realized how much it was helping under braking. Then I bought a 968 with a torque biasing diff. Rebuild it, it was a better, faster car (my business partner set a couple of track records with it, and won the PCA 944 SP3 championship a few years ago with it). But dear lord, going into 10A at Road Atlanta at about 140, braking hard, I've never been so scared in my life. Rear end was all over the place. A friend who was behind me thought I was going to lose it. Sure I was able to adjust the dampers a little to help slow the weight transfer, but that was right where I learned about the advantage of a plate diff. It seems with bigger and faster cars, most seem to go to torque biasing, but I"ll take a good plate diff any day of the week.
UP markets this for track use and states that most average daily drivers would not see any benefits. However they also state that it has a benefit in inclement weather such as snow and ice - and I assume that's not referring to racing in snow and ice. I wonder how this lsd would perform in winter driving conditions?
Clivew
Member
A helical diff will give you no benefit on snow and ice compared to the stock open diff. A helical diff can only transfer across the axle a multiplication of the torque that the wheel with least grip can use for traction. So zero traction means a multiplication of zero torque is transferred to the wheel with more grip, same as an open diff.
Also former Evo owner here- this not completely true. I live in snow country have probably drove an evo more than 40k miles on just snow. It is brilliant here, like no other vehicle I've ever driven. There is traction on snow and ice, especially with modern snow tires, and the helical and clutch pack lsd will happily deliver unbelievable acceleration both in a straight line and sideways. I don't own a Tesla, but this topic is why I'm lurking. I'm interested in m3 snow dynamics and this thread gives me hope.
Clivew
Member
Yeah, perhaps I oversimplified my answer. For some reason I was assuming summer tyre usage on snow, which is how most people (wrongly) in the UK do it.
With proper snow tyres, which produce decent grip on snow and ice, a helical diff will be able to transfer torque across the axle.
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