Pseudo limited slip differentials

[The Boston Dangler]

This is actually F1 tech, the new McLaren MP4 doesn't use an LSD.

If they can get the software calibrated, this will be better and cheaper than mechanical systems.

regarding f1 diffs, they're partially electronically controlled with 3 parameters (entry, mid-corner, and exit) set by the driver. when the governing body outlawed all forms of driver aides, the teams successfully lobbied to keep the higher-performing e-diffs by demonstrating how much less 1 adjustable e-diff cost compared to a truckload of purely mechanical diffs. the money they save gets blown up elsewhere 😛

 

[HarryLui]

How do you power slide with software LSD? Oh wait, you can't.

 

[Nyati13]

My Subaru Outback has an e-diff for the front wheels and it really does seem to work well. It has worked noticeably for me on a few occasions on wet roads, snow, and dirt/rocks.
I would still prefer a mechanical LSD on both axles, but the e-diff is absolutely better than nothing.

 

[halik]

I read an article about the next BMW 3 series having an open differential that used a combination of stability control plus rear brakes to make it work similar to a limited slip differential.

Why don't they actually use a limited slip differential? Is there that much of an efficiency or cost advantage with using an open differential?

Hah bullshit, my CLK had that kind of "limited slip" differential too. If the wheel starts slipping, it hits the brake.

 

[foghorn67]

Hah bullshit, my CLK had that kind of "limited slip" differential too. If the wheel starts slipping, it hits the brake.

Like all SC/TC systems, YMMV.
Some are seamless, others practically stick a flag out and wave hi.

 

[Railgun]

That's pretty much what they have now and it sucks. I had a 335i and while capable on track, I would very much have rather had an LSD. In the snow? Yeah, that solution is horrible.

 

[alkemyst]

My M3 has a mechanical LSD that also ties into the computer. Plus Dynamic Stability Control.

I have the Competition Package which throws one more 'preset' DSC setting in between total safety mode (you can't really spin the tires even) and totally off.

It's designed for tracks and does a good job of staying out of a driver's way until he is really getting out of control.

Once you get to that level, you can turn it all off.

 

[halik]

My M3 has a mechanical LSD that also ties into the computer. Plus Dynamic Stability Control.

I have the Competition Package which throws one more 'preset' DSC setting in between total safety mode (you can't really spin the tires even) and totally off.

It's designed for tracks and does a good job of staying out of a driver's way until he is really getting out of control.

Once you get to that level, you can turn it all off.

The LSD is actually purely mechanical, there's no computer feedback to its function. No mtrack mode for me, 01 🙁

 

[alkemyst]

Track mode or not, it ties into DSC.

 

[halik]

Track mode or not, it ties into DSC.

The Limited Slip Diff doesn't tie into it, take a look underneath the car - there's nothing electronic on it.
The DSC unit uses hall sensors in the hubs to keep track of the wheels, regardless of what kind of diff you have in the back.

Shear between the two axles preses fluid against the clutches:

 

[alkemyst]

The Limited Slip Diff doesn't tie into it, take a look underneath the car - there's nothing electronic on it.
The DSC unit uses hall sensors in the hubs to keep track of the wheels, regardless of what kind of diff you have in the back.

Shear between the two axles preses fluid against the clutches:

Those sensors at the hubs know what the rear end is doing.

Argue with BMW when they explain the whole M Active deal.

 

[halik]

Those sensors at the hubs know what the rear end is doing.

Argue with BMW when they explain the whole M Active deal.

Well the sensors pick the spin rates of each hub, that's got nothing to do with the diff though. Any car with abs/stability control has that, including E46s with open diffs.

The M track mode just lets a lot more slippage happen before DSC cuts throttles and possibly hits the brakes. There's a thread about it over at m3forum.

 

[Jumpem]

My Subaru Outback has an e-diff for the front wheels and it really does seem to work well. It has worked noticeably for me on a few occasions on wet roads, snow, and dirt/rocks.
I would still prefer a mechanical LSD on both axles, but the e-diff is absolutely better than nothing.

I have not got my Outback stuck yet to see how it works. I know on my Frontier, it would cause all four wheels to have power and spin.