Limited Slip Differential working with traction control?

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Limited Slip Differential working with traction control?

Post by martin10chk » Wed Sep 19, 2018 8:55 pm

I have tried to read all I can on this topic but would like some insight from those who have actual experience.

I do not intend to go to a track. I intend to keep electronic safety features engaged on the road (so Sport, rather than Sport + I guess).

Will I derive any benefit from an LSD? I suppose my intuition is that in a race to act between electronics (the traction control) and mechanics (the LSD) the electronics will win. In which case the LSD will never do anything! Is that incorrect. Thanks

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Re: Limited Slip Differential working with traction control?

Post by marco_polo » Wed Sep 19, 2018 9:07 pm

An LSD is far more responsive than the electronics.

The LSD is proactive, starts locking up when torque is applied from the driveshaft. The electronics are reactive, slamming the rear brakes on (not very helpful when trying to press on) only after the rear ABS sensors have finally decided one wheel is spinning faster than it should be.

Once you've fitted an LSD, it's rare to see the TC light flashing.
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Re: Limited Slip Differential working with traction control?

Post by martin10chk » Wed Sep 19, 2018 9:09 pm

marco_polo wrote:
Wed Sep 19, 2018 9:07 pm
An LSD is far more responsive than the electronics.

The LSD is proactive, locking up when torque is applied from the driveshaft. The electronics are reactive, slamming the rear brakes on after the rear ABS sensors have finally decided one wheel is spinning faster than it should be.

Once you've fitted an LSD, it's rare to see the TC light flashing.
Excellent - that's what I want!!

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Re: Limited Slip Differential working with traction control?

Post by Jahjaman » Thu Sep 20, 2018 8:57 am

marco_polo wrote:
Wed Sep 19, 2018 9:07 pm
An LSD is far more responsive than the electronics.

The LSD is proactive, starts locking up when torque is applied from the driveshaft. The electronics are reactive, slamming the rear brakes on (not very helpful when trying to press on) only after the rear ABS sensors have finally decided one wheel is spinning faster than it should be.

Once you've fitted an LSD, it's rare to see the TC light flashing.
Not quite, MP. I see the TC light all the time, and I know TC is working even when the light doesn't flash.

The TC is reactive, in that the first instances it will let you wheelspin. But once it detects wheelspin, it will turn proactive and start to cut power before wheelspin occurs. The skinny rear tyres are never enough to suppress 500Nm. It will wheelspin in the dry, and TC will eventually cut the fun so it stops wheelspinning until you restart the car.
This is much more obvious in the wet.

Also note, it is well known that TC acts to cut power even without the TC light flashing. So it would be working without you even realising.

This is also the reason why the "throttle body reset" works for some people, and for many it doesn't work. It's because there's nothing wrong with the TB setting, it's simply the TC working without you realising it.
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Re: Limited Slip Differential working with traction control?

Post by marco_polo » Thu Sep 20, 2018 9:08 am

You must be running a Quaife then, I've got a Drexler.
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Re: Limited Slip Differential working with traction control?

Post by THETYRANT » Thu Sep 20, 2018 9:09 am

I dont know about the F series cars but when i fitted a Quaife LSD to my last E87 130i it wasnt as fast to react as the electronics when all nannys were left on and you drove aggressively, hence TC light was on similar amount in my experience, but of course when you switch the nannys off you were able to make better progress than previous as the LSD would lock after wheel slip keeping you moving forward, and sideways sometimes!.

To me if not going on track and your not turning the nannys off you wont see a huge benefit from fitting a LSD so save your pennys, at least a helical type LSD like the quaife which takes a little time to vector the torque once it detects wheel slip, im not sure how the offical BMW LSD on F series cars reacts but from what MP says above maybe its faster to react than the Quaife units.
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Re: Limited Slip Differential working with traction control?

Post by Jahjaman » Thu Sep 20, 2018 9:45 am

marco_polo wrote:
Thu Sep 20, 2018 9:08 am
You must be running a Quaife then, I've got a Drexler.
Yes :)

Perhaps Drexler locks up much earlier than Quaife and therefore does not trip TC?

Is this the same for the MP LSD?

Edit: actually, MP - it doesn't matter whether it locks up or not - when it wheelspins, both wheels spin at the same time - so the Quaife has already done its job of transferring torque between wheels well before slip occurs.

It's just that there is insufficient grip from the tyres. And so TC will light always be active.
Last edited by Jahjaman on Thu Sep 20, 2018 10:05 am, edited 2 times in total.
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Re: Limited Slip Differential working with traction control?

Post by NISFAN » Thu Sep 20, 2018 10:04 am

Just adding my 2 cents to this thread, my Quaife acts immediately and seems to match MP’s description of how a LSD works in these cars.
I see much less intrusion from TC, yes I can still get the light flashing, but often it is stability control kicking in due to yaw angle, not wheel spin as such. Flashing light in response to wheelspin is quite amusing, as it usually occurs a second after the onset of wheelspin which has now ended before it even gets the chance to react. An indication that e-lsd is not fast enough to act like a proper lsd.


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Re: Limited Slip Differential working with traction control?

Post by GeeDee » Thu Sep 20, 2018 10:13 am

I have the Quaife and drive with nannys off 90% of the time (the rest of the time is when the limiter is on) and so don't see the TC light at all owing to the light being the same as the DSC Off light although I still feel as if the electronics are exerting some control but apparently not when wheelspin occurs under acceleration as that seems to be quite hard for me to detect until I get a kick sideways or it becomes obvious the revs are increasing too fast - obviously, I'm talking fractions of a second here rather than wheelspin all the way down the road wondering why I'm not accelerating. :lol:
Edit: ....and deep breath. Reading this again and I realise some punctuation would have been good - Sorry :oops:
Last edited by GeeDee on Thu Sep 20, 2018 11:30 am, edited 1 time in total.
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Re: Limited Slip Differential working with traction control?

Post by Jahjaman » Thu Sep 20, 2018 10:36 am

Clearly, as can be seen from others running Quaife too, my rear tyres are simply not gripping very well.
I'm running 38psi cold. So I'll drop it to 34 and try that :)
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Re: Limited Slip Differential working with traction control?

Post by marco_polo » Thu Sep 20, 2018 10:59 am

Yup, sounds like you have a traction/tyres issue, rather than a diff or TC problem. Last time I was at Santa Pod, I was using below 30psi to aid a decent hole-shot, if you're drag racing / in 1st gear.
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Re: Limited Slip Differential working with traction control?

Post by mouse140i » Thu Sep 20, 2018 12:05 pm

I have Drezler LSD and when being silly I get traction starting to get involved.

Example of over/power steer out of T junction. If I over cook the throttle or miss the oversteer a little then TC will help out.

I am 99% time driving with a quick press of the top TC button so I'm in Traction mode on the dash.

I've even had the secondary traction control/ESP/whatever light appear on the dash when being really silly.

I've also managed to spin the car when in Traction and the nannies haven't been able to help out.

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Re: Limited Slip Differential working with traction control?

Post by docwra » Thu Sep 20, 2018 2:04 pm

Ive got an M3 diff on an E82 and Im not really sure what youre all on about - the traction control does exactly the same as when it was an e-diff, cuts in at a given amount of slip. There is effectively more grip so youre going faster when it does, but it will still kick in with enough abuse.

As THETYRANT says, IMO having an LSD but leaving the e-diff coded on is a waste of time.

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Re: Limited Slip Differential working with traction control?

Post by GeeDee » Thu Sep 20, 2018 2:34 pm

docwra wrote:
Thu Sep 20, 2018 2:04 pm
As THETYRANT says, IMO having an LSD but leaving the e-diff coded on is a waste of time.
Not a complete waste of time.

I read somewhere a while back that you could code out the e-diff, rightly or wrongly, but I can't help thinking in the event of an accident you're at risk from your insurance company finding out.
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Re: Limited Slip Differential working with traction control?

Post by docwra » Thu Sep 20, 2018 3:49 pm

GeeDee wrote:
Thu Sep 20, 2018 2:34 pm
docwra wrote:
Thu Sep 20, 2018 2:04 pm
As THETYRANT says, IMO having an LSD but leaving the e-diff coded on is a waste of time.
Not a complete waste of time.

I read somewhere a while back that you could code out the e-diff, rightly or wrongly, but I can't help thinking in the event of an accident you're at risk from your insurance company finding out.
OK, Ill rephrase that. I had an M3 LSD fitted with e-diff still on and it was a waste of time. I then coded it out and its much better.

If the insurance co are going to delve into your settings then you probably need to make sure your tyre pressures are stock too :lol:

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