[dradernh]

Originally Posted by 2slo

How do you code out the eLSD?

BPM Sport coded mine: http://www.bpmsport.com/services/cod...s-service.html.

It was done at the shop that installed most of my upgrades. I paid $500 to have eLSD and EDC coded-out.

[4Hockey4]

I'm having hard time deciding on M performance vs others, I can get done for $2,400 out the door at BMW, vs. other ones considerably more.

[msej449]

I've not coded out the eLSD because I see it as the final line of defense against total loss of control (this on public roads - track is a different situation).

In a way, it is how the car should have left the factory: with a physical LSD keeping me safe up to a certain point, when the eLSD would intervene if I'd made a complete hash of a manoeuvre and was going to crash out. That is, the car had gone beyond any action of mine being able to retrieve the situation and the eLSD would then save me (within the realms of physics).

I know that for track situations, many people simply don't want the eLSD to intervene, ever, because of itself that could destabilise a manoeuvre over which they had control. But for drivers like me who don't track, I couldn't see the logic of turning it off.

I have a suspicion that engineers at BMW sometimes design the car on an assumption that various parts are there which in the end turn out to be optional. The European High Beam Assist (HBA) is an example. I think the standard beam is set too low by default for someone without HBA - once you have the full Euro HBA you realise that the two ar complementary (HBA maintains a high beam on the driver's nearside but drops it on the oncoming side whan a car approaches; it drops high beam in urban lit areas; and it 'boxes' the car in front in a dark oblong with both beams at high, using the tail lights.) If you don't have HBA then the standard beam is too low and full beam is blinding.

Similarly, I think the designers always intended the car to carry a physical LSD. In which case the eLSD only intervenes when you've really started to lose it and for most public road drivers, they're effectively outside the envelope of being able to control the car. The eLSD srt of complements the physical LSD. But in the end, the bean-counters decided to drop the physical LSD and so you're left with an eLSD which in wet and cold winter tarmac, is intervening a lot more than it was intended to, as it constantly compensates for the absence of the physical LSD.

[Aspen235]

[QUOTE=2slo;26747727]

Originally Posted by harma24

It's now 7:15 (6:15 where you are I think). Please tell me they have finished by now.[/QUOT

The diff was in but there's some epoxy involved apparently with a 2 hour cure time. The exhaust was still on the ground. .

Do you know any more about what was epoxied? I am getting mine installed on Monday at an indy shop. I have not heard of the need to glue anything and can't think of why it is needed.

[Jaxom]

That's great you were able to get that price.

I'm located in Phoenix and after calling all three BMW dealerships in the area and trying to get them to fight each other.... the lowest price I was able to get was $3k for the full install.
Maybe I should drive down to Tuscon.. haha no probably not worth it for $250.

Note: They all initially asked me anywhere between 3.8k - 4.2k when I first called.... Still haven't done the install but that's the quote I currently have.

[aerobod]

Originally Posted by msej449

I've not coded out the eLSD because I see it as the final line of defense against total loss of control (this on public roads - track is a different situation).

In a way, it is how the car should have left the factory: with a physical LSD keeping me safe up to a certain point, when the eLSD would intervene if I'd made a complete hash of a manoeuvre and was going to crash out. That is, the car had gone beyond any action of mine being able to retrieve the situation and the eLSD would then save me (within the realms of physics).

I know that for track situations, many people simply don't want the eLSD to intervene, ever, because of itself that could destabilise a manoeuvre over which they had control. But for drivers like me who don't track, I couldn't see the logic of turning it off.

I have a suspicion that engineers at BMW sometimes design the car on an assumption that various parts are there which in the end turn out to be optional. The European High Beam Assist (HBA) is an example. I think the standard beam is set too low by default for someone without HBA - once you have the full Euro HBA you realise that the two ar complementary (HBA maintains a high beam on the driver's nearside but drops it on the oncoming side whan a car approaches; it drops high beam in urban lit areas; and it 'boxes' the car in front in a dark oblong with both beams at high, using the tail lights.) If you don't have HBA then the standard beam is too low and full beam is blinding.

Similarly, I think the designers always intended the car to carry a physical LSD. In which case the eLSD only intervenes when you've really started to lose it and for most public road drivers, they're effectively outside the envelope of being able to control the car. The eLSD srt of complements the physical LSD. But in the end, the bean-counters decided to drop the physical LSD and so you're left with an eLSD which in wet and cold winter tarmac, is intervening a lot more than it was intended to, as it constantly compensates for the absence of the physical LSD.

The eLSD is only enabled when DSC is fully switched off, though, and isn't overall responsible for vehicle stability, only traction. Basically the eLSD tries to prevent a rear wheel from spinning by applying the brake on that wheel, but without any regard for any sensor input other than the pulse sensor on the slipping wheel. The programming is just trying to apply brake to slow the wheel with the higher number of pulses to the speed of the wheel with the lower number of pulses.

When DSC is on the stability program takes input from all wheel sensors plus yaw, steering angle and acceleration and apply brakes to all wheels as necessary to try and damp any vehicle motion away from the commanded line. DTC programming is a little less aggressive in controlling wayward motion, allowing more driving wheel spin that is beneficial when on low traction surfaces.

[albertw]

Originally Posted by msej449

. . . it is how the car should have left the factory: with a physical LSD keeping me safe up to a certain point . . .

I have trouble understanding exactly how an LSD is supposed to keep you safer than an open differential.

Here's how I see it, but I would be happy to learn from others whose understanding is deeper. Let's ignore straight line acceleration and consider only acceleration while turning, where the risk is spinning out.

With an open diff, if you add more power than the tires can take, the inside wheel spins. This can cause a slide if you are cornering near the traction limit, as less traction is available from the inside tire to help turn the corner. However, the outside wheel does not spin so the rear just slides out gradually and controllably.

With an LSD everything is fine as you add more power, until you reach the point that both wheels spin. Then there is a very large loss in cornering traction and no non-spinning wheel to stabilize the slide. How is that safer than the case of the open diff?

[wt888]

Originally Posted by albertw

I have trouble understanding exactly how an LSD is supposed to keep you safer than an open differential.

Here's how I see it, but I would be happy to learn from others whose understanding is deeper. Let's ignore straight line acceleration and consider only acceleration while turning, where the risk is spinning out.

With an open diff, if you add more power than the tires can take, the inside wheel spins. This can cause a slide if you are cornering near the traction limit, as less traction is available from the inside tire to help turn the corner. However, the outside wheel does not spin so the rear just slides out gradually and controllably.

With an LSD everything is fine as you add more power, until you reach the point that both wheels spin. Then there is a very large loss in cornering traction and no non-spinning wheel to stabilize the slide. How is that safer than the case of the open diff?

Let's say the open diff breaks loose at 50 "units" of traction while accelerating. 50 being used to turn the car, 50 being used to accelerate. The LSD won't break loose until 75 units of traction with the same tires. That means you can add more power in the corner. This also changes the balance of the car - the rear now has more grip than the front so that the front doesn't have way more traction than the rear.

The breakaway is also much smoother. With the open diff, it was jerky, which led me to make a big correction. When you upset the balance of the car it's harder to control. Now that I have the LSD, I can feel the rear of the car move around but it's smooth, giving me lots of warning before I break away, making it much easier to control.

It's like tires - some have smooth breakaway which inspires confidence. Some have abrupt breakaway.

[albertw]

I don't follow the numerical argument. You can't use 50% of traction for turning and then have 75% available for acceleration, regardless of the type of drive system you have. Perhaps you could try to explain that a different way.

Maybe what you mean is that if you are using 50% of traction for turning you can't use the whole remaining 50% for acceleration with an open diff because the inside rear wheel has less weight on it than the outside so it spins before you get to 50% of total traction going to acceleration. (I see that as a good thing, not a problem, since I don't drive on the track.)


Maybe your issue with jerky breakaway came from driving in Sport. In my hands it does really weird things as you approach the cornering traction limit and then add power. Jumpy isn't exactly the word I would use, but close enough. On the other hand, in Sport + I find the breakaway to be smooth and the slide to be easily controllable (open diff, Pirelli runflats with factory square setup).

Another possible difference is that I have never tried to slide the car while using only 50% of traction for cornering. I do it when I'm at 80 - 90% traction for cornering, so the slides come easily and predictably.

[aerobod]

Perhaps throttle cut at traction loss that happens in Eco, Comfort and Sport but not in Sport+, DSC Off and less so in DTC are the reason for lack of smooth transition of grip?

[2slo]

[QUOTE=Aspen235;26756836]

Originally Posted by 2slo

Do you know any more about what was epoxied? I am getting mine installed on Monday at an indy shop. I have not heard of the need to glue anything and can't think of why it is needed.

I am not sure. It might have been the thread lock on something - 2 hour cure time sent me to thinking epoxy but I'm not sure he said that word.

[albertw]

Originally Posted by aerobod

Perhaps throttle cut at traction loss that happens in Eco, Comfort and Sport but not in Sport+, DSC Off and less so in DTC are the reason for lack of smooth transition of grip?

Well, I haven't tried to slide the car in Eco or Comfort. It Sport I didn't try it enough times to figure out what was happening, but it seemed that rather than letting the rear end step out when I added throttle it moved both the front and rear about two feet sideways. It felt like it was being done by brakes, but I really don't know. I didn't sense much of a throttle cut. I do know I wasn't quick enough on the steering wheel to stop it from moving sideways.

I forgot about DSC off when making my last comment. With my setup it doesn't work very well either for getting the car to oversteer a bit. If I'm near the traction limit for cornering, then add a bit of gas to step out the rear, I can feel the car begin to oversteer slightly when the eLSD brakes the inside rear so it hooks up again and the slide stops abruptly. That's probably the jerky behaviour that WT888 complained about. I suspect the eLSD is meant mainly for low traction conditions - ice, snow, mud.

For my driving style Sport + lets me induce and easily control a bit of oversteer without any perceptible computer modulation of the brakes or throttle.

[Poochie]

Originally Posted by msej449

I've not coded out the eLSD because I see it as the final line of defense against total loss of control (this on public roads - track is a different situation).

In a way, it is how the car should have left the factory: with a physical LSD keeping me safe up to a certain point, when the eLSD would intervene if I'd made a complete hash of a manoeuvre and was going to crash out.

That's exactly how I read it implementation also:


.