LSD in an AWD???

[stinger1168]

Has anyone tried to put an LSD in the rear differential of the AWD (not RWD) Stinger? Can it be done?

 

[mldavis2]

What's the purpose?

 

[Marc Collins]

What's the purpose?

Same as on the RWD!

Should have been an option from the get go. Standard on Genesis G70 AWD sister car.

Of course it will fit, but is there a software update required to prevent interference from the brake-based torque vectoring?? That's the big question...

 

[mldavis2]

Same as on the RWD!

The RWD needs it for traction. AWD doesn't. Only possible reason is to be able to drift a little easier. The AWD will drift quite nicely with TC turned off.

 

[Kazz]

Currently, traction control for the rear wheels in the AWD models without LSDs is brake-based. That means that if either rear wheel starts to spin brake is applied. I'd MUCH rather have the mechanical system take care of as much of that as possible as my goal is to accelerate, not brake. I don't care how "good" the system is at using the brakes, you end up with less traction, less acceleration, period.

 

[mldavis2]

0-60 times are equivalent for RWD and AWD according to reviews. The TC system will transfer power front before braking for a rear wheel slip.

 

[Marc Collins]

0-60 times are equivalent for RWD and AWD according to reviews. The TC system will transfer power front before braking for a rear wheel slip.

Sorry, [MENTION=328]Kazz[/MENTION] is right. It's about handling and torque vectoring, which can be controlled electronically with the LSD, too, by the way (see Nissan GT-R, Subaru WRX STi, etc.). Brake-based torque vectoring is the poor cousin to doing it properly with a LSD. Lots of lower-end cars have and more will get the brake-based version because it's just tweaking the programming of the stability control software that's already there. Not to mention wearing the brakes prematurely. Wait until you see how expensive the Brembo's are before dismissing that one...

And 0-60 is irrelevant--it's about cornering. However, you are right that the AWD car won't do a 1970's style one-wheel burnout peeler because the fronts kick in on dry pavement, but on slippery surfaces you are dragging one rear wheel (on and off repeatedly using the stability control strobing the brakes) to allow the opposite one to gain traction instead of locking them and letting nature do the job properly.

 

[Kazz]

0-60 times are equivalent for RWD and AWD according to reviews. The TC system will transfer power front before braking for a rear wheel slip.

There is a maximum amount of power split that will be sent to the front - 40%? I don't know specifics, but it's not even 50/50.

 

[mldavis2]

You are assuming that braking is an override to torque vectoring. Only if all 4 wheels are slipping would brakes come into play and then only after power reduction. Let's get one of the Kia engineers in on this one.

 

[Kazz]

I guess I don't understand what you're saying. The instant any of the four wheels starts to slip, braking is applied to it.

 

[VegasStinger]

Currently, traction control for the rear wheels in the AWD models without LSDs is brake-based. That means that if either rear wheel starts to spin brake is applied. I'd MUCH rather have the mechanical system take care of as much of that as possible as my goal is to accelerate, not brake. I don't care how "good" the system is at using the brakes, you end up with less traction, less acceleration, period.

I completely agree with this, sad thing is even BMW and Mercedes have gone to electronic LSD instead of mechanical LSD.

 

[stinger1168]

The main purposes of having an LSD in the rear diff of an AWD system is to aid in handling when applying power when coming out of a turn, to get power to the ground in an efficient manner in slippery conditions and in straight line acceleration with really high power applications. The Stinger has a decent setup. You have the center diff which applies power front and rear as needed. As the rear wheels lose traction, it sends some power to the front wheels. The front and rear diffs are "open" differentials. If one wheel on a particular axle has traction and the other is on a slippery surface, all the power gets sent to the wheel on the slippery surface. So if both front and left rear wheels are on ice and both right wheels have good traction, the wheels on ice spin like crazy and the wheels with traction....do nothing. Enter brake torque vectoring which is what the Stinger has and most affordable awd suv's have. If the wheel on a particular axle starts to spin like crazy, the brake on that spinning wheel is applied to such an extent that the open diff sends power to the wheel with traction. SOME of these systems are ok but they do prematurely wear on the brakes and heat them up. These systems are more reliable and durable as they have less moving parts and are easier on axles and universal joints. They are also cheaper to build. Other systems use limited slip differentials (LSD's). With an LSD, when a wheel starts slipping, the LSD shifts power to the wheel with traction. It doesn't use the brakes to do this, there are clutches and/or other mechanical parts that redistribute the power. With some of the more expensive vehicles, when you go on their websites to build your vehicle, there are options to add an LSD to the rear diff of some of their AWD systems. So not only does the power go from front to rear but ALSO side to side, usually with just the rear end. They could also do it with the front but it adds stress to the axles and universal joints. In some systems, they can apply all power, if necessary, to one rear wheel if that's the wheel with traction. This has obvious benefits in slippery or off road applications but also helps on a track. Especially if it's been raining. Let's say you're accelerating out of a left hand turn on a race track. The weight of the vehicle shifts to the right side of the vehicle. In particular, the right rear. With open front and rear diffs, the left side front and rear wheels may start to spin with the power being applied. The Stinger will apply the brakes on those spinning wheels to try to divert power to the right side of the vehicle to accelerate out of the turn. With an LSD, the brakes aren't applied and it will redistribute the power to the right side wheels where the weight has shifted to. The brakes aren't being applied so the engine isn't fighting the brakes as the brakes are slowing acceleration, the brakes don't wear as quickly AND the brakes will be cooler so they won't fade when you need them to slow before the next turn.

I think I got everything. Someone let me know if I made a mistake but this is my understanding of this. I hope this explains things.

 

[Marc Collins]

The main purposes of having an LSD in the rear diff of an AWD system is to aid in handling when applying power when coming out of a turn, to get power to the ground in an efficient manner in slippery conditions and in straight line acceleration with really high power applications. The Stinger has a decent setup. You have the center diff which applies power front and rear as needed. As the rear wheels lose traction, it sends some power to the front wheels. The front and rear diffs are "open" differentials. If one wheel on a particular axle has traction and the other is on a slippery surface, all the power gets sent to the wheel on the slippery surface. So if both front and left rear wheels are on ice and both right wheels have good traction, the wheels on ice spin like crazy and the wheels with traction....do nothing. Enter brake torque vectoring which is what the Stinger has and most affordable awd suv's have. If the wheel on a particular axle starts to spin like crazy, the brake on that spinning wheel is applied to such an extent that the open diff sends power to the wheel with traction. SOME of these systems are ok but they do prematurely wear on the brakes and heat them up. These systems are more reliable and durable as they have less moving parts and are easier on axles and universal joints. They are also cheaper to build. Other systems use limited slip differentials (LSD's). With an LSD, when a wheel starts slipping, the LSD shifts power to the wheel with traction. It doesn't use the brakes to do this, there are clutches and/or other mechanical parts that redistribute the power. With some of the more expensive vehicles, when you go on their websites to build your vehicle, there are options to add an LSD to the rear diff of some of their AWD systems. So not only does the power go from front to rear but ALSO side to side, usually with just the rear end. They could also do it with the front but it adds stress to the axles and universal joints. In some systems, they can apply all power, if necessary, to one rear wheel if that's the wheel with traction. This has obvious benefits in slippery or off road applications but also helps on a track. Especially if it's been raining. Let's say you're accelerating out of a left hand turn on a race track. The weight of the vehicle shifts to the right side of the vehicle. In particular, the right rear. With open front and rear diffs, the left side front and rear wheels may start to spin with the power being applied. The Stinger will apply the brakes on those spinning wheels to try to divert power to the right side of the vehicle to accelerate out of the turn. With an LSD, the brakes aren't applied and it will redistribute the power to the right side wheels where the weight has shifted to. The brakes aren't being applied so the engine isn't fighting the brakes as the brakes are slowing acceleration, the brakes don't wear as quickly AND the brakes will be cooler so they won't fade when you need them to slow before the next turn.

I think I got everything. Someone let me know if I made a mistake but this is my understanding of this. I hope this explains things.

Explained perfectly. G70 has it standard equipment because it's supposed to be/is being marketed as "sporty." So should the Stinger have it at least as an option.

 

[Marc Collins]

You are assuming that braking is an override to torque vectoring. Only if all 4 wheels are slipping would brakes come into play and then only after power reduction. Let's get one of the Kia engineers in on this one.

You don't seem to understand how these things work. The braking is the torque vectoring because there is no LSD.

 

[stinger1168]

Explained perfectly. G70 has it standard equipment because it's supposed to be/is being marketed as "sporty." So should the Stinger have it at least as an option.

WOW! I didn't realize the G70 had a rear LSD with the AWD system... That would be a great option for the Stinger and I don't think it would increase the price that much for just the LSD unless it was included with other options as a package.

And thanks! I've been doing a bit of research over the years as to WHY some awd systems are better than others. I've found that some (especially the older ones) are just awful and not worth getting at all, most are meh...ok and a few are really great. There are some pretty good videos on youtube but even there you gotta look out. Someone will show how great one system is and how bad another is in comparison but they don't tell you that the good system has the upgraded awd system with a rear LSD (electronic or mechanical). I've recently discovered that there's Quattro and then there's Quattro with a rear LSD. X-Drive and X-Drive with a rear LSD etc etc... Does the average Joe need the LSD. Probably not but if you do even some light off roading, the rear LSD is really nice to have. I've been looking at the Audi S5 Sportback Quattro and guess what? It has an OPTIONAL rear LSD! It would be a great option to have with the Stinger. It's on their RWD cars, it wouldn't take much to put it on the AWD cars and change the software a little. I'd pay a little more for it myself.

 

[mldavis2]

You don't seem to understand how these things work. The braking is the torque vectoring because there is no LSD.

You are correct only on the Stinger. I had assumed that because GKN differential was used that the term "torque vectoring" was the active vectoring system used by that system. Apparently Kia cheaped out and went with an alternative brake system to aid in the system rather than using clutches. The terminology is misleading because "torque vectoring" is generally not associated with a hybrid braking assist. I understand quite well how these systems work, I simply did not realize that Kia went the brake route. The "real" GKW clutch differentials used in true AWD torque vectoring systems are heavier and require different computer functioning that uses brake assist.

 

[Marc Collins]

You are correct only on the Stinger. I had assumed that because GKN differential was used that the term "torque vectoring" was the active vectoring system used by that system. Apparently Kia cheaped out and went with an alternative brake system to aid in the system rather than using clutches. The terminology is misleading because "torque vectoring" is generally not associated with a hybrid braking assist. I understand quite well how these systems work, I simply did not realize that Kia went the brake route. The "real" GKW clutch differentials used in true AWD torque vectoring systems are heavier and require different computer functioning that uses brake assist.

Subaru already has this same system. I haven't bothered to look, but if everyone else doesn't have it yet, they will soon. As mentioned above, great for the average Joe. Not a suitable replacement for someone looking for a real LSD. It should be an option on any higher-trim Stinger.

 

[jackcrep]

Audi S5 Sportback Quattro and guess what? It has an OPTIONAL rear LSD! It would be a great option to have with the Stinger.

Germans from GRIP car program did a back to back test of Audi S5 with LSD and Kia Stinger. On a track Audi was quicker by 3.1 sec with a time of 1:13.8 vs 1:16.9. 16bhp less and 100kg of weight less for Audi - they claim it won on a track because of LSD. Anyway Audi cost almost 30 000? more with more or less the same equipment, apart from LSD of course (1350?). So yeah, LSD gives a big advantage when you pull away from a corner. Do you need it? Depends on you, so having such an option would be nice. Especially that European rivals have it.

 

[jackcrep]

forgot to paste a link
https://youtu.be/vcsYqR9_Smk

 

[Marc Collins]

Germans from GRIP car program did a back to back test of Audi S5 with LSD and Kia Stinger. On a track Audi was quicker by 3.1 sec with a time of 1:13.8 vs 1:16.9. 16bhp less and 100kg of weight less for Audi - they claim it won on a track because of LSD. Anyway Audi cost almost 30 000? more with more or less the same equipment, apart from LSD of course (1350?). So yeah, LSD gives a big advantage when you pull away from a corner. Do you need it? Depends on you, so having such an option would be nice. Especially that European rivals have it.

Especially nice to have it at least as an OPTION when sister car G70 comes with it standard (in Canada anyway).