LSD = More traction control?

[7Andrei7]

A few weeks ago I swapped my open diff for an LSD. It's the one that came standard in the "frigid"zone on all EU GT Lines. Mine, same model, came with the open diff as I live in the "temperate" zone of the EU.
Since then, I can definitely feel an improvement in corner exit and the car clearly rotates way faster, especially at low speeds. I can now easily do a donut, something which was impossible with my 2.0 engine and 255 tires.

However, I also see a way more jumpy TC action. I drive 90%+ in comfort mode and with the open diff I could floor it, no worry, and there was almost no TC stepping in. Even below 4 Celsius like the past 2 weeks.
Now, if I'm making a change of direction or it's a little bumpy while I am flooring it (4k+ rpm and 100+ kph) the TC steps in and cuts the power. With the car in Sport mode I could not get the TC to step in. Only in comfort mode.

There could be another explanation: I just bought a new pair of rear winter tires (same as what I had before but they are a new set). Maybe they are more sensitive or the rubber moves around more because they are new. It would be weird but it's worth noting.

Or is there another explanation for this? Could it be because now it's both wheels that slip at the same time and TC decides to cut power? Anyone understands the mechanical logic?

 

[Volfy]

I just noticed this thread today...

This one first puzzled me a good bit. Then the more I think about it, the more it starts to make sense.

Okay... The way Traction Control works is by using the ABS wheel sensors to detect excessive spin in one or more driven wheels. The ECU then typically does one or both these two things:

1. cuts power (actually more specifically TORQUE) to try to calm the spinning wheel(s) down and hopefully regain traction again.

2. apply brake to the driven wheel that is spinning, to limit its "slip".

Back when you were on open diff, your car was much more likely to spin one driven wheel - not both. Therefore, your car's TC mitigation strategy is much more likely to deploy #2 above, instead of the more draconian step of cutting torque all together. What you might notice is the ABS pump actuating very briefly. Depending on how you drive and how loud your car is or tires are, you might not even hear it much.

Now that you've switched to LSD, it is doing its job to limit slip on any one side, so... the consequence could be that TC might detect BOTH driven wheel spinning, thus cutting torque becomes the more appropriate mitigation strategy.

This is pure conjecture on my part, of course, not having first hand experience with your car.

As I've mentioned previously, our '19 2.0T has had the LSD retrofit for more than a year now, driven almost daily (in comfort mode), and has gone through several track events and AutoXs (in sport mode with TC/SC disabled). I've yet to feel any negative behavior that could remotely be blamed on the diff.

In your case... I would wonder if the gear oil you used might be letting the clutch pack lock up too aggressively. Lots of owners have it happen to their LSD Stinger/G70s, though they typically complain about the diff chattering on slow turns. Who know... your setup might manifest in a different way. I would squirt in a little bit of CRC® Trans-X® Posi Trac® Limited Slip Gear Oil Additive, 7 Fl Oz to see if that calms your LSD down, and in turn, your TC.

 

[7Andrei7]

Thank you for your inputs!
Already replied to you privately but will leave this here in case anyone else will encounter this problem.

The issue seems to be fixed. Yesterday I took out both wheel speed sensors and cleaned them. There was a bit of dirt on both of them. I stuck them back in and went on a newly opened section of ring road, which has almost no traffic, and did some tests.

I did a few hard pulls from 100 to 170kph and it was as if the car was relearning how to deploy TC. On the first 2 pulls it cut power aggressively and flashed.
Then it started to flash but there was no obvious cut in power. The revs were still going up while the TC was flashing. This also happened 2 times.
And finally, for the last 3 pulls there was no reaction at all.
The surface was damp and about 6 degrees celsius. I always kept the gas pedal fully depressed, beyond the kick down button.

I hope this is it and I don't need to do anything more. My dealer confirmed that the HECU module (which apparently controls ESP, ABS and TC) is identical on all 2.0 Stingers and there are 4 types of ABS sensors: Standard suspension 2WD / Adaptive Suspension 2WD / 4WD / Right hand drive. There is no differentiation based on the type of diff.

 

[Volfy]

Glad to hear the problem isn't persisting. It does sound like it's just the wintery conditions causing heartburn for the TC/SC systems in your car. I'm so glad I don't have to deal with that any more. That said, I do missing pulling donuts in empty university parking lots, after a fresh snow storm, before getting shooshed away by campus security.

We were snow/ice drifting, before drifting was even a thing.

 

[Snicklefritz]

I always kept the gas pedal fully depressed, beyond the kick down button.

You and Fred Flintstone, hey? I thought the kickdown switch was it, no, "To the kickdown switch, and beyond!"

 

[Volfy]

LOL... realistically, if I want to conduct any sort of tomfoolery, I wouldn't be in Comfort mode anyway. OTOH, at the track, it's always Sport mode, with Traction Control and Stability Control switched OFF. Supposedly, according to some YT reviewers, Kia doesn't really turn TC and SC completely off, even when the driver explicitly disables the TC/SC. From what I can gather, if any of it is left active, it's very minimal and not at all intrusive. The car will let you go wild, if you insist. I had no problem swapping ends a couple of times, albeit unintentionally.

On public roads, for me, Comfort Mode is for exactly that... comfort.

 

[7Andrei7]

You and Fred Flintstone, hey? I thought the kickdown switch was it, no, "To the kickdown switch, and beyond!"

You can depress it to the kick down switch or you can go beyond that switch and hit the "floor". The point was to emphasise that there was no pedal travel left.

 

[Volfy]

We just did the LSD swap on the '23 2.5T over the holidays, along with installing coilovers. Similar to the LSD swap on the '19 2.0T, I did not notice any odd TC or SC intrusion in normal driving. Weather is relatively warm here (65F yesterday) and roads are clear, so no compromised traction anywhere. I'm not comfortable gunning it on public streets, but we have an AutoX coming up this weekend, so we'll see how it does with some proper hooning.


This is the second LSD swap I've done and while I'm all-too-happy to have done them, I sure as heck would much rather not have to drop the diff again, if I could possibly help it. It's a full 2-day job. So... just to make sure, I changed out the oil seals on both side. Curiously, LEFT and RIGHT sides are different Part Numbers, and they are even color-coded differently, but I can't tell the difference between them. Oh well. It's done.

 

[7Andrei7]

If you can, maybe do this test at the AutoX:
In a straight line, while in comfort mode, floor it from about 55mph to 100mph. See if the TC is flashing or cutting power.

Mine still does it. I was hoping cleaning the ABS sensors would fix it but it did not. Under those conditions and at that speed the LS diff should behave exactly the same as an open diff. It still doesn't make sense to me.

Thank you!

 

[Volfy]

I won't be able to do that at the AutoX. Just about all of them are set up to keep speed low... and newbs safe. Most cars just stay in 2nd gear. For track sprints, that's easy to do... usually some 2-3 times per lap on the straights, but I don't ever run Comfort mode in that setting. That said, I should be able to find a section of fwy where I can sprint up to 100mph without irking the ire of the Law. I'm currently letting the coilovers settle a bit before I get an alignment done. After that, I'd do your test and let you know.

 

[7Andrei7]

Thank you!
I will make a trip to the dealer to have some tests done and a full reset of all computers.

 

[Volfy]

I did several test pulls like you described and there was no indication of TC/SC intrusion. Just a little turbo lag, followed by swift/smooth acceleration. I even did a couple more from lower starting speed, just for giggles. I'm not a straight-line speed demon, so this is actually the first time I've goosed the 2.5T since I bought the car. Amazing how quickly the speedo needle climbs.

Conditions were 55F, dry concrete pavement. 235/45R18 all-seasons (not exactly super grippy tires). Map 0.

Also, I'm pretty sure I've done similar pulls like that with the 2.0T after LSD swap. Also uneventful as well.

 

[7Andrei7]

Interesting! Were you in comfort mode?

 

[Volfy]

Yes, per your request. Plus that's what I drive in 99.99% of the time on daily drive. Occasionally, I might flick into sport mode to set up for a fun corner worth taking spiritedly, then right back to Comfort mode.

 

[7Andrei7]

Thank you so much! I use mine exactly the same

I'm happy you don't get the same TC intrusion. At least now I know it's definitely an abnormal behaviour of my car. Either some sensor or software or maybe tires. I'll get tot the bottom of it.

 

[rtv900]

or maybe tires. I'll get tot the bottom of it.

I don't experience this in my Kia, but I can tell you for certain in my Z06 I get MAJOR TC issues with my winter tires on that car. It's night and day compared to the summers. It's a manual and obviously way more low end torque and rear drive only, but I have to roll on the gas way smoother with the winters on or TC kicks right in.
It's because the system frankly is too sensitive, so the flex in the thick tread of the winter tires makes the ECU think that they are slipping for that brief second if I get on it too quick. All it takes is that split second trigger and the system cuts throttle for probably 1-2 seconds. It's annoying as hell.

I also run snows on my Kia currently and do not have that issue. I think the AWD, lower power and automatic trans simply soften the power delivery. And the system may also be less sensitive

 

[Volfy]

I just did my second fill with about 4 Oz. Of Trans-X. I heard the humming noise for a little while after initial test drive, then I don't hear anything any more after that. Tried a couple of pretty tight U-turns and no noise at all. Pretty sure the initial noise is just the new fluid working to get between the clutch plates.

 

[7Andrei7]

I went to the dealer today and did a complete check of the systems. There were no faults and they said that they can't check if there are any differences in software between the different Stingers (with or without the limited slip diffs). They also claimed they can't code anything on the car or install a different software (based on a different VIN number) even though the HECU module is the same.
They were quite unhelpful tbh. The whole thing took 10 min and they charged 75€. At least they did a full reset of the computers.

Sadly, the car behaves the same. There are really random moments when the TC steps in and cuts power. This is in a straight line and at high speed (over 110kph). Car kept in comfort mode. For example I could do 3 pulls with no problem and then the 4th time the TC stepped in.

I can't believe that the car is able to spin both rear wheels at 120kph with only 245hp and 353nm of torque.
So I'm pretty baffled. Maybe this is how all Stingers with an LSD act in Europe. And the open diff Stingers trigger the TC later because it first uses the torque vectoring to brake the first spinning wheel and thus limiting the total acceleration.

I have to wait for summer to see if it will behave any differently. If it still cuts power then I think there is a difference in software tuning and I will need to find a way to write the different software on my car.
It's all pretty annoying.

 

[rtv900]

I can't believe that the car is able to spin both rear wheels at 120kph with only 245hp and 353nm of torque.

there's zero chance this car can break those tires loose at that speed
I could go WOT in my Z06 at 4000 rpm's putting 650 foot pounds to the road and it won't spin the 335's on the rear

 

[7Andrei7]

there's zero chance this car can break those tires loose at that speed
I could go WOT in my Z06 at 4000 rpm's putting 650 foot pounds to the road and it won't spin the 335's on the rear

But would your TC cut power in that scenario, on winter tyres? I know it's a totally different car, I'm just curious.