[Mysticality]

Simply put why not? A clutch pack "should" be able to transfer 100% of an engine's torque if it is designed that way. If I were to push the AWD lock button and the front wheels were elevated what would happen? Would the clutch pack lock completely together to allow all engine power to flow from the motor, to the transmission, to the transfer case, through the driveshaft, and into the rear differential where it is split to the two rear wheels, or will the computer sense that "too much" torque is coming through the clutch pack, torque beyond the ability of the friction materials on the clutch plates to grip, and will begin pulsing the clutches to prevent them from pulling too hard on each other?

50% to front, 50% to rear.
The front is always engaged so 100% of power cannot be sent to rear, ever.
Not unless you break both front drive shafts.

 

[phillyguy]

50% to front, 50% to rear.
The front is always engaged so 100% of power cannot be sent to rear, ever.
Not unless you break both front drive shafts.

I do not have a diagram of the Sorento AWD system, but I do have one in front of me from the Hyundai Santa Fe (from hmaservice.com) which I am assuming is identical in design and operation to the Sorento.

It looks to me like power flows from the engine, to the transmission, and from there to what looks to be a unified front differential and transfer case (they label it as "transfer"). From there the power can flow into the rear prop shaft which goes to the awd coupling device and to the rear differential, finally reaching the rear wheels.

It looks to me that if there were no traction for the front tires, because they were on wet ice, or were elevated, or some extreme situation, that the engine torque would flow into that hybrid transfer case/front diff, the front diff would take zero torque since the front wheels have zero traction, and all remaining torque would be directed through the driveshaft through the coupling device and into the rear differential.

Am I misunderstanding the diagram I am looking at? I would post the image but I am not sure how to here. In what amounts to the artificial situation I am presenting here - front wheels elevated - would it be possible to direct all torque rearward? Or am I still misunderstanding something simple?

 

[Mysticality]

Truth be told, I'm not 100% sure, having never had both front wheels off the ground.
In my times offroad, I have had one wheel each, front and rear (alternate sides), off the ground and without traction control they just spun.
I know that the TC brakes the spinning wheels, causing torque to be applied to the wheels with grip.
That being said, I have been in situations where, when the engine is pushed from a standing start on a gravel road, when the turbo kicks in the wheels would have an immense push and lose all grip, then the rear would activate and the vehicle would literally take off. The looks you get when the passengers get whiplash still makes me smile.


EDIT: I do remember one situation where the front of the vech. was hung up over a ditch I couldn't quite cross. Put the AWD lock on, put it in reverse, floored it and it popped right out, easier than I expected.
Didn't have time to brake and nearly smashed the wing mirror on a tree, but better than being stuck!

 

[klrman]

Late post, but is the awd in the 2013 sorento the same as the 2011?

Also curious is traction control should be turned off when going up a steep
snowy, icy grade? I turn off traction control on my 2005 crv in those conditions up our 1/2 mile mountain driveway and it seems to work. If I leave it on, you can feel the engine being dragged down by the braking.

 

[phillyguy]

Late post, but is the awd in the 2013 sorento the same as the 2011?

Also curious is traction control should be turned off when going up a steep
snowy, icy grade? I turn off traction control on my 2005 crv in those conditions up our 1/2 mile mountain driveway and it seems to work. If I leave it on, you can feel the engine being dragged down by the braking.

Most stability control systems cut the throttle in addition to pulsing the brakes. Your bogging down is probably due to the lost throttle, not to the braking.

 

[klrman]

Most stability control systems cut the throttle in addition to pulsing the brakes. Your bogging down is probably due to the lost throttle, not to the braking.

Nice to know technically what is happening thanks. So it makes sense then that I should be switching off the stability control on my 2013 sorento as well in those conditions on a steep icy incline.

 

[phillyguy]

Nice to know technically what is happening thanks. So it makes sense then that I should be switching off the stability control on my 2013 sorento to then in those conditions on a steep icy incline.

Steep icy inclines can be really tricky. In *theory* a perfect stability control system should help you up, but in *practice* nearly all of them are WAY too stupid to figure out what to do and just end up cutting throttle and killing your momentum so you never get up the hill. I have never personally had good luck with stability control on icy inclines. The new AWD system in the Hyundai Santa Fe has a function tied in with the stability control that will brake an individual slipping wheel (they erroneously call it torque vectoring). *That* system may be quite helpful moving up an icy incline.

Bit of a non sequitur but I have always found a G80 rear diff in chevy trucks to be very helpful in getting up icy hills. Could just be where I have been, but having a lock across an axle has always seemed more beneficial to me than locking the two axles together on icy hills.

 

[klrman]

Steep icy inclines can be really tricky. In *theory* a perfect stability control system should help you up, but in *practice* nearly all of them are WAY too stupid to figure out what to do and just end up cutting throttle and killing your momentum so you never get up the hill. I have never personally had good luck with stability control on icy inclines. The new AWD system in the Hyundai Santa Fe has a function tied in with the stability control that will brake an individual slipping wheel (they erroneously call it torque vectoring). *That* system may be quite helpful moving up an icy incline.

Bit of a non sequitur but I have always found a G80 rear diff in chevy trucks to be very helpful in getting up icy hills. Could just be where I have been, but having a lock across an axle has always seemed more beneficial to me than locking the two axles together on icy hills.

Yeah, in "theory" they all sound amazing lol. Where I live, momentum is very important and killing the run never works. that's why I always turn my SC off in my crv on the steep run. I learned the hard way on the coldest winter day.

We also have a 94 full size chevy blazer that we use to clean snow in winter on our road. It always stays in 4H as we have logging chains on the rear and nothing stops them.

 

[KLS]

klrman, the biggest problem with snowy roads is the poor grip from the OEM tires. Don't expect much from these Kumho KL21s. I've upgraded my winter rubber to Hankook i*cept evo.

Try your climb with the traction control both on and off, and please give us the results. It is likely different from your '05 Honda. By the way, stability control and traction control are different. Traction control cuts power to a spinning wheel, either by a bit of brake and/or a bit less power (engine power cut). Stability control tries to straighten us out in a side skid by braking and/or cutting power to the tires on one side to try to pull us straight. Both are generally a good idea and neither is perfect.

I'm still trying to get a feel for the AWD system in our Sorentos. The magic box is the electrically actuated clutch assembly just forward of the rear differential. I find it hard to believe that the dry clutches are made to slip on demand, and I'm not at all sure about pulsing on and off. I haven't had enough time on steep slippery roads to be able to feel exactly what's happening. You do know that the 4wd button on the dash is speed-related?...it only activates below 15 mph, deactivates at 19, reactivates at 15, or at speeds something like that. Above those speeds we are dependent on the computer to know when to switch into 4WD. (I call AWD a system with a center differential or viscous coupling that allows a speed differential between the front and rear drive shafts. Our cars do not have that. I call cars where the front & rear driveshafts locked together 4WD. This is what our cars do (note that the book explains a possible shudder on dry roads when cornering slowly and 4WD is turned on, a locked 4WD characteristic), unless the clutch assembly modulates somehow, all a mystery. Car makers call AWD or 4WD whatever the company marketing department wants to call it.)

How does your KLR do on that icy hill? Have you got studs for it? It can be helpful for Kia answers if you put a bit more info into your profile...year & model car, and at least the country you're in.

 

[klrman]

klrman, the biggest problem with snowy roads is the poor grip from the OEM tires. Don't expect much from these Kumho KL21s. I've upgraded my winter rubber to Hankook i*cept evo.

Try your climb with the traction control both on and off, and please give us the results. It is likely different from your '05 Honda. By the way, stability control and traction control are different. Traction control cuts power to a spinning wheel, either by a bit of brake and/or a bit less power (engine power cut). Stability control tries to straighten us out in a side skid by braking and/or cutting power to the tires on one side to try to pull us straight. Both are generally a good idea and neither is perfect.

I'm still trying to get a feel for the AWD system in our Sorentos. The magic box is the electrically actuated clutch assembly just forward of the rear differential. I find it hard to believe that the dry clutches are made to slip on demand, and I'm not at all sure about pulsing on and off. I haven't had enough time on steep slippery roads to be able to feel exactly what's happening. You do know that the 4wd button on the dash is speed-related?...it only activates below 15 mph, deactivates at 19, reactivates at 15, or at speeds something like that. Above those speeds we are dependent on the computer to know when to switch into 4WD. (I call AWD a system with a center differential or viscous coupling that allows a speed differential between the front and rear drive shafts. Our cars do not have that. I call cars where the front & rear driveshafts locked together 4WD. This is what our cars do (note that the book explains a possible shudder on dry roads when cornering slowly and 4WD is turned on, a locked 4WD characteristic), unless the clutch assembly modulates somehow, all a mystery. Car makers call AWD or 4WD whatever the company marketing department wants to call it.)

How does your KLR do on that icy hill? Have you got studs for it? It can be helpful for Kia answers if you put a bit more info into your profile...year & model car, and at least the country you're in.

Hi there KLS. I updated my profile and noticed we're neighbours and both have Vstroms lol. I have studded Hankooks on my CRV and they always do the job year after year in Winter around here.

I just purchased the Sorento in Vegas last week and drove it back to BC. Passed BC inspection yesterday, drove it home up my hill and will store it in my warm garage for the Winter. Too shiny and good looking to abuse it for the first Winter Not much snow on our hill yet, but very icy and with the stock tires it ran up the mountain with ease and TS was not turned off so that was a bonus.

While it's parked for the season, I want to get to the bottom of the transmission "clunk" that happened twice on the way back to canada. Both times were when it was shifting from 1st to second moving slowly. I did noticed that an ecm upgrade was suggested when we got the warranty printout but I want to do more research if that upgrade is actually worth doing or not as otherwise it just runs way to good to mess with it. Also read that it is common on the sorento's but I don't buy that yet. Need to do some more research this Winter.

Yes, I read that in the manual that at 19 mph the awd lock will disengage so will always try and remember that. Not sure myself how it all works on the Sorento. You're right, TS and SC are different and sometimes I forget that. Pretty sure my CRV has SC as it kicks in on the flats if I go a little too fast on the ice in a corner. Doesn't work up our hill though so we always need to turn it off before climbing.

My KLR runs fine up the hill. I just screw sheet metal screws in my D606's and that does the trick on the hard ice. Got to love those KLR's.

 

[putercents]

Thank you for all the helpful explanations. Just wish we could stud our tires here in Ontario. Of all the dumb laws.

 

[KLS]

What winter rubber do you run? I've found modern studless winter tires to be quite good. Studs are better on glare ice, but otherwise, I'm happy with studless. I just put a set of Hankook i*cept evo studless tires on the Sorento (haven't been on snow yet), and I have had great results with Bridgestone Blizzak DM-V1 studless tires on my truck.

Here's some customer results from Tirerack
http://www.tirerack.com/tires/surveyresults/surveydisplay.jsp?type=W&VT=LT
http://www.tirerack.com/tires/surveyresults/surveydisplay.jsp?type=W&VT=C

Not included in the lists above are the brands they don't sell...Nokian, some Hankook, Cooper (& Mastercraft and Dean), some others.

 

[whodat90]

I have a couple of questions about this. When you write:




Where is the parasitic drag coming from? It seems to me that the only extra moving parts in FWD mode are the added transfer case to direct torque rearward, and the rear driveshaft. These can't weigh more than a few pounds apiece so it would seem to me that they would not add too much resistance to the drivetrain. Is there something I am missing here or are these small parts enough to induce a significant drop in the fuel economy?

Simply put why not? A clutch pack "should" be able to transfer 100% of an engine's torque if it is designed that way. If I were to push the AWD lock button and the front wheels were elevated what would happen? Would the clutch pack lock completely together to allow all engine power to flow from the motor, to the transmission, to the transfer case, through the driveshaft, and into the rear differential where it is split to the two rear wheels, or will the computer sense that "too much" torque is coming through the clutch pack, torque beyond the ability of the friction materials on the clutch plates to grip, and will begin pulsing the clutches to prevent them from pulling too hard on each other?

Did you ever test this? It would seem most logical for it to be able to "pulse" off an on, meaning a 0 or a 14.4v reading. Its hard to imagine it using some intermediate voltage as that would be a lot of slip which one would think would rapidly degrade the friction material on the clutch plates.

Finally is the system employed in the Sorento the Borg Warner iTM3e system used in the Hyundai Santa Fe? I have looked around for confirmation of this but have not seen anything definite. Thanks.

Ok, the parasitic drag comes from a couple of places. The thing to remember is that the driveshaft is always spinning, and the rear axles are always spinning, and the rear diff is always spinning (when the car is moving) The magic of the system is that they aren't always connected to each other. Then there's the additional weight of the system, according to kia the weight difference between the fwd and awd is ~175lbs.

Next, the clutch pack/power transfer. This gets a bit tricky. A clutch can transmit 100% of available power, as does the clutch in any car or motorcycle (btw I'm a Vstrom owner too!) The thing is, the clutch in this system is a ramped dog style clutch. The electrical system just activates it a little bit, then a set of rollers slide up ramps and compress the clutch pack as they go. It's a great system in that the amount of torque it transmits is directly related to how much resistance it encounters. I haven't had a chance to get under and throw the multimeter on it, but with a ramped dog clutch I don't believe that varying the amount of voltage/current/PWM to the clutch would make any effective change; as soon as it starts to engage, the rest is mechanical. Kind of like that G80 that was mentioned, it's flywheel activated. As soon as the wheelspin reaches some threshold, BANG! its engaged totally.

And I'm not sure exactly what 'system' they call the one in the kia, sometimes they sell the same thing with different software packages and give it a new name, sometimes they have totally different systems with the same concept and call it the same. Sorry.

 

[whodat90]

I do not have a diagram of the Sorento AWD system, but I do have one in front of me from the Hyundai Santa Fe (from hmaservice.com) which I am assuming is identical in design and operation to the Sorento.

It looks to me like power flows from the engine, to the transmission, and from there to what looks to be a unified front differential and transfer case (they label it as "transfer"). From there the power can flow into the rear prop shaft which goes to the awd coupling device and to the rear differential, finally reaching the rear wheels.

It looks to me that if there were no traction for the front tires, because they were on wet ice, or were elevated, or some extreme situation, that the engine torque would flow into that hybrid transfer case/front diff, the front diff would take zero torque since the front wheels have zero traction, and all remaining torque would be directed through the driveshaft through the coupling device and into the rear differential.

Am I misunderstanding the diagram I am looking at? I would post the image but I am not sure how to here. In what amounts to the artificial situation I am presenting here - front wheels elevated - would it be possible to direct all torque rearward? Or am I still misunderstanding something simple?

Here is where the term 'engine power' and 'torque' become unclear. Power will always flow to the wheel with the least resistance. Regular 2wd car with one wheel on ice, that wheel will spin and take all the 'power.' Add a limited slip diff in the mix however, and the wheel speed difference will cause some of the power to flow to the higher resistance of the wheel with traction, and will hopefully be enough to move the car. Throw a locker in there and it gets complex. It's either receiving 50% of the power (since both wheels now receive equal power) or 100% of the power (because no power is being put to the ground through the wheel on ice) The Sorento is a FWD vehicle that transitions to a part-time 4WD vehicle on demand, which averages out to AWD. If you jacked the front wheels off the ground and tried to drive, the gee whiz electronics package would see the front wheels spinning and activate the clutch, and you'd immediately have a bad day as the vehicle drove off the jacks. (BTW, jeep actually has a procedure for that to check the 4WD system in their WJ series Grand Cherokees. There are lots of warnings in that book) Instead of looking at 'power' or 'torque', it's easier to consider it as potential torque. The key to moving is to apply torque to the ground. If you have no resistance, you can't have torque. If you're spinning a tire, there's no resistance so almost none of your power and torque are being delivered to the ground. Activate the traction control systems (lockers, AWD, etc. ) and it tries to find a wheel with resistance it can send power to.

As for the actual stability control, it's the one thing I don't like about kias. High end systems operate under the concept of 'we're going to control your traction to maintain control' and do neat things like differential braking, differential torque splitting, etc. The kias operates under the concept of 'we're going to lower your power to meet available traction' and simply starts cutting the engine power till the wheelspin stops. Effective but terrifying. A while back I rented an optima, and there was a bump in the drive between my hotel and the busy street I was trying to pull out into. Every single time I tried to pull out it'd see the bump/turn as a threat and kill my engine for a few seconds. Ended up just having to turn it off. Now for going up a snowy hill, the reason you'd turn the TCS off is because as I said, the system is designed to match your power to the traction you have right now. If instead you turn it off, you can go looking for traction of your own by spinning the tires and trying to dig down to more traction. This past Friday I went out and played a bit on some snowy roads, and was able to easily get all four wheels spinning, then the traction control would start killing the power until I could accelerate slowly away. However, on the way home from that I managed to do something that caused the vehicle to slip unintentionally, and the kia immediately killed the power, activated the abs and awd, and recovered control within 10 feet. I was impressed.

 

[KLS]

I think it would be more clear if we just said that the system will control how the engine "drives" the front wheels or drives all four wheels. Or something simple and clear like that. If the front wheels slip under power, the system will tell the engine to drive the fronts and rears at the same time. This also happens under 19 mph when the 4wd button is pushed. Is this good enough for most folks?

 

[klrman]

(btw I'm a Vstrom owner too!) .

Thanks for the nice tech info about the AWD. Good to learn something new everyday. We also know that there are now officially three vstrom owners on this forum as well, which of course means that vstrom owners have excellent taste in choosing cars

 

[Zxenith]

....
The kias operates under the concept of 'we're going to lower your power to meet available traction' and simply starts cutting the engine power till the wheelspin stops...

Does that mean the Sorento does not employ the selective wheel brakes?
If not, how does simply cutting the power solve the problem, in the context of over-steer or the rear spinning out or is that another system?

 

[PLP]

there is a mix of power cut and selective wheel brakes. Does the power is completely cut when ESC kicks in? I do not know. I guess it depends on situation, but from MY personal experience with Rondo, power is always 100% off and only brakes are activated.
And yes, it does its job.

How it does? Simply by torque and momentum. If you slide out of tight right turn (you slide to the left) braking left wheels will shift momentum to the right straightening the car trajectory. If you oversteer to the other side - opposite will happen. And then depending on the angle of the steering wheel and your speed and current direction of movement - some wheel will slow down more some not at all.

Drive with one side on snow, one on pavement. Hit the brakes (non-ABS) you will feel how car wants to go.



It really looks funny when you look on it from a side (still standing) and a driver in oncoming car fights with ESC. You literally see each wheel being activated in side slide...

 

[Zxenith]

@PLP thanks for the info, Appreciated.

 

[Jstorresn]

Hi guy I'm own a 2011 Kia sorento EX 2.2 diesel, week ago I have an issue with the AWD, I don't have rear traction and is a problem when I go off road because the front wheels drift I didn't have this problem before. I hope you can help me. Thank you!!