[whodat90]

Crew Chief.

 

[hvaleagues]

Roger that.

 

[Mysticality]

@Whodat- If you want any specific data etc, I could always take a look next time I take the Sorento off-road... (Its a regular occurrence )
Have found that the only thing that holds it back is the tyres. (Am running OEM "Roadian"s; can't afford the A/T's or M/T's I dream about.)

 

[whodat90]

I've been an off-roader for a long time, I just finally changed what I do it in. The Kia for me is specifically a family runabout, and the paint is too pretty/fragile to play offroad. My GMC just weighs too much, if it gets stuck at all it's 7000lbs stuck so that doesn't get to play either. I bought a dirtbike (xr400) and a four wheeler (300EX) for my dirt fix, figuring that if I total either one of those I'd be out less than if I dented the Sorento. :0

 

[Mysticality]

Heheh, nice.
Sorento is a quite capable vehicle... So long as you don't get two wheels stuck in the air. -.-
The traction control system seems quite, well... Bad.
And the ABS seems to be a system-wide affair... Not individual wheels. If I slam the brakes on and one rear wheel looses grip, all four wheels are lessened on the brakes, not just one... This probably leads to the dodgy TC when the alternate wheels are 'flying high'.

 

[PLP]

Heheh, nice.
Sorento is a quite capable vehicle... So long as you don't get two wheels stuck in the air. -.-
The traction control system seems quite, well... Bad.

Since when you drive off road with ESC activated?? Turn it OFF. It helps.

And the ABS seems to be a system-wide affair... Not individual wheels. If I slam the brakes on and one rear wheel looses grip, all four wheels are lessened on the brakes, not just one...

ABS on one wheel only?

Just think of it - one wheel looses its grip. How is it possible? Unless very deep turn when one of the wheels lifts of the ground.
Otherwise it is impossible due to one thing. Rear wheels follow front wheels.
So, if one side looses grip, how can you expect the system (ABS) to keep high pressure on the other side? This would end up with spinning car.
Besides, ABS is designed to keep braking force even on all axles.

Yes, ABS is 4 channel, but only for ESC. ESC is allowed to brake one or more wheels at a time only. ABS itself does not do that. It will detect slippage of one wheel, but will adjust braking force to all wheels to maintain straight course.

And all ABS's work like that.

 

[Mysticality]

Since when you drive off road with ESC activated?? Turn it OFF. It helps.

Since you can't get diff locks for the Sorento.

ABS on one wheel only?

Just think of it - one wheel looses its grip. How is it possible? Unless very deep turn when one of the wheels lifts of the ground.
Otherwise it is impossible due to one thing. Rear wheels follow front wheels.

I can take some photos for you, if you'd like. Or a video, even.

Yes, ABS is 4 channel, but only for ESC. ESC is allowed to brake one or more wheels at a time only. ABS itself does not do that. It will detect slippage of one wheel, but will adjust braking force to all wheels to maintain straight course.

And all ABS's work like that.

I would love it if ABS didn't work like that, almost had a collision driving down a mountain road, because the ABS decided that it wasn't going to let me brake at all, coming up to a sharp bend, because of a couple of leaves on the road.

 

[venturey]

Hi just wondering about towing on the awd, do you need to tow on a dolly or can it be towed flat. thanks

 

[conwelpic]

Hi just wondering about towing on the awd, do you need to tow on a dolly or can it be towed flat. thanks

see page 6/22 in the owners manual

On 4WD vehicles, your vehicle must be towed with a wheel lift and dollies or flatbed equipment with all the wheels off the ground.

CAUTION
The 4WD vehicle should never be towed with the wheels on the ground. This can cause serious damage to the transaxle or the 4WD system.

On 2WD vehicles, it is acceptable to tow the vehicle with the rear wheels on the ground (without dollies) and the front wheels off the ground.

 

[roshan]

Thanks Whodat, great job explaining. But I am a little confused about the AWD. Could you lead this child to knowledge by explaining the difference between an AWD system and a 4WD system?
My understanding was that in a 4WD system the front 2 wheels and the rear 2 wheels act as separate independent units and get engine power to them in an ratio according to the need, wheras in an AWD system all 4 wheels act as individual units which receive power as needed. In which case, how is it possible to have an AWD without a limited slip differential?
(apologies in advance if my question is stupid! )

 

[Mysticality]

4WD systems are usually either part-time or full-time, and include a transfer case (i.e. 2H/4H/4L) comprised of normal running gear and specialized low-range running gear... Usually the low range is on a ratio of 2:1.
Think of it this way: You max out 1st gear at a speed of 40KM/h... In 1st gear low-range, you max out 1st gear at 20KM/h. This allows for more torque at a lower speed, needed when going offroad.
4WD systems are mechanical.

AWD systems are basically just a way of giving all wheels power, be it for more performance, better handling etc.
They do not have a transfer case and are more often than not, full-time systems. The user cannot control them. (In the case of the Kia's, they can however. To some degree.)
AWD systems are usually electronic.

Think of it this way:
Land Rover Defender = Full-time 4WD with transfer case, diff lock, and other offroad things.
Nissan Patrol = Part-time 4WD with all the rest.
Audi TT = AWD
Mitsubishi Lancer = AWD

There are more examples but those are just a few.

 

[whodat90]

The line between AWD and 4WD can get murky, and some systems combine both. The general delineator is the low range gearset. AWD does not have a low range, 4WD does. This then leads to the other more generalized differences. 4WD drivetrains are usually much more stoutly built than AWD; AWD drivetrains are usually much lighter. I'll go into the internals of a few of the cases that I'm most familiar with to show the differences.
The GM autotrack transfer case, as found in my Yukon. It is a hybrid of AWD/4WD. It is an electronically actuated transfer case, which has 2WD, 4WD high, 4WD Low, and auto modes. I was going to write up a power transfer chart, but I found this on performancetrucks.net which does a great job:
In the 4HI mode, the power flow to the rear propshaft (10) is the same as it is in the 2HI mode. To deliver power flow to the front propshaft (13) during the 4HI position, the transfer control module commands the encoder motor (15) to apply the clutch to a calibrated torque. The encoder motor (15) turns the control actuator lever shaft (14). A brake in the encoder motor (15) holds the control actuator lever shaft (14) in the full clutch position. The control actuator lever shaft (14) is cam designed and the cam action moves the clutch lever (4). The clutch lever (4) pivots on the clutch lever pivot studs and moves toward the clutch apply plate, to engage the clutch. As more pressure is applied to the clutch apply plate, the clutch discs are compressed. Using inner clutch discs, which are engaged with the clutch hub (5), and the outer clutch discs, which are engaged with the clutch housing (6), the power flow is delivered to the clutch housing (6). The clutch hub (5) is splined to the rear output shaft (9), and the clutch housing (6) rotates on a needle bearing on the rear output shaft (9). The chain drive sprocket (7) is splined to the clutch housing (6). The power flows from the drive sprocket (7), through the chain (11), to the chain driven sprocket. The driven sprocket is splined to the front output shaft (12). The power flow is delivered to the front propshaft (13) through the front output shaft (12).

During the Auto 4WD mode, the power flow is the same as it is in the 4HI mode. Except, during the Auto 4WD mode, the encoder motor (15) rotates the control actuator shaft lever (14) to the correct torque level positions. Rotating the control actuator (14) to the various positions changes the clutch torque level. When a difference of front propshaft (13) to rear propshaft (10) speed is recognized, the transfer case control modules command for more, or less clutch torque.

exploded view of np246 ? - PerformanceTrucks.net Forums

All props to the original poster.

 

[whodat90]

Next up is the NV/NVG/NP 249 quadratrack from early jeep grand cherokees. This had 4WD high and 4WD low. This was a true fulltime all wheel drive system. It's greatness was also it's greatest failing, the power transfer through it's viscous coupling.

The Viscous coupling, or VC, is used in many different AWD systems so it deserves a little explanation. the VC is a sealed device with an input and output, either splined or geared. It is closely related to a clutch, in that it is filled with interleaved discs, one set splined to the input and one to the output. The magic is that it's filled with a Non-Newtonian fluid - Wikipedia, the free encyclopedia non-newtonian fluid. Think silly putty. Now imagine that this is sitting between two wheels. If the wheels are spinning the same speed, there is no speed difference between the two halves. If there is a slight speed difference, there is still a small amount of resistance. If one starts to spin relative to the other however, the fluid begins to thicken just like silly putty and it starts to lock the two together, transferring torque between the two. As soon as the speed difference is gone, the fluid goes back to a more fluid state.

Ok, the early 249 had the power go from the transmission to the input of the tcase, then through the chain to the reduction gearset and then the VC. The VC then output to the front and rear driveshafts. The genius in this was that it was all wheel drive, all the time. You could drive around on the street in 4WD low, which is exciting. The failure was that the VC was a wear item, and when it failed would fail either open or closed. If it failed open, then you could spin both front tires or both rear tires, and not transfer any torque to the other axle. This was annoying but preferable to failing closed. When it failed closed, it locked the front and rear axles together, allowing no slippage. This is bad because when you go around a corner, the front wheels travel a further distance than the rear. If you don't allow for that speed difference, it binds the drivetrain and leads to premature tire wear, all manner of strange noises, and can lead to breakage in the drivetrain.

Next up is the 242. This had 2WD, 4WD high, 4WD fulltime, 4WD low. In all modes other than 4WD fulltime it operated as a normal transfer case. In 4wd Fulltime however, instead of locking the front and rear outputs solid, it ran them through an open differential. This acted exactly like the previously mentioned 249 with a VC that has failed open.

Finally is the quadradrive system. This has 4WD and 4WD Low. This is an engineers wet dream, as it is a fully mechanical torque sensing automatic torque transferring drivetrain which can put power wherever it's actually needed and usable. Note that in the other ones I didn't really talk about anything other than the transfer case, as the rest of those systems were just regular axles and differentials. The qdrive however is a complete system. In general, you can think of it as a fulltime system with open differentials, and this is how it acts. However the clever bit is a series of oil pumps and clutch packs. Any pump operates by a speed difference between two items. The qdrive has a pump in each diff (front, center, and rear) which is connected to opposite shafts. Front and rear diffs use the axles, center uses the front and rear driveshafts. The output from each pump is fed to a clutch pack, which also couples each pair of shafts. In operation it acts like this: Imagine the vehicle with three wheels on ice, one on pavement. You apply power, and immediately one rear wheel spins. The spinning causes a speed difference between the two axleshafts, causing the pump to pump fluid. The fluid then locks the clutch pack causing power to be transferred to the other wheel on that axle. It's also on ice, so they both spin. This spinning causes a speed difference between the front and rear driveshaft, activating the pump/clutch pack combo in the transfer case. This sends power to the front axle, where the other tire on ice starts to spin. Once again, the speed difference activates the pump and clutch, now sending all available power (variable based on wheelspeed, viscosity, etc; never 100% but a goodly portion thereof) to the wheel on asphalt, pulling the vehicle off the ice. As soon as the other wheels hit pavement, they stop spinning and the lack of wheelspin releases the clutches and it's a regular open diff again. Pure genius.

One final note, is that 4WD systems almost always include a Neutral position, and AWD doesn't. This neutral is somewhat like the neutral in a transmission, in that it totally de-couples the driveshafts from the engine/transmission.

 

[roshan]

Thanks Whodat and Mysticality, I think I managed to grasp atleast the fundamentals of the systems. However these mechanics are way too complicated to my somewhat rudimentary mechanical knowledge!!!!

I am waiting to take delivery of my Sorento which is equipped with AWD. Will see if it behaves any different to my Sportage!

Cheers!

 

[Mysticality]

Thanks Whodat and Mysticality, I think I managed to grasp atleast the fundamentals of the systems. However these mechanics are way too complicated to my somewhat rudimentary mechanical knowledge!!!!

I am waiting to take delivery of my Sorento which is equipped with AWD. Will see if it behaves any different to my Sportage!

Cheers!

No worries.

I often use our AWD Diesel offroad and the only thing that lets me down is the tyres. (Still got stock on it. -facepalm-)
On the road its a dream... Never loses traction, even when I try!

 

[puddy]

I am a little confused my sorento has 4wd badges and was a xm version made august of 2010 for the uk market

But Jan 2011+ the badging changed from 4wd to awd

Was that just a badge change or a different type drive fitted?

Puddy
ps all UK sorento are made in Korea

 

[Mysticality]

I am a little confused my sorento has 4wd badges and was a xm version made august of 2010 for the uk market

But Jan 2011+ the badging changed from 4wd to awd

Was that just a badge change or a different type drive fitted?

Puddy
ps all UK sorento are made in Korea

My Sorento also has 4WD badges (Aussie, thus Korean made)
Manf. date: 01/10
Its the same system, still AWD... I'm not sure why they kept the 4WD badges. Perhaps to continue the bloodline from the previous ('real' 4WD) Sorento?

-Matt

EDIT: I see you have the 6spd manual... How is it?
Personally, I would have loved one but the end decision of purchase was not mine and thus we were stuck with an auto.

 

[newsorentogu]

I much prefer the 4wd on my old blazer that i sold, than the awd on my 2012 sorento (i love the new truck, just wish i could have full-time 4wd on it at all speeds, for driving in slippery conditions). just my two cents.

 

[mbutkus]

I tromp on the gas at this stop sign with a right turn incline road a few blocks from my house when the weather is wet or snowy and my XS with AWD jumps around this turn with no problem. That's AWD. Any FWD car just spins. My Saturn with AWD (very different setup) would spin the front a bit then the back would kick in, but you usually had to be heavy on the gas to get that back to lock-up.
So far no problems with the SX AWD. Very little slip before you get going.
With 26mpg on the highways... an AWD I can like.

 

[phillyguy]

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

The disadvantages of this system are that you take a gas mileage hit; there is a fair amount of parasitic drag.

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?

Since it's connected by a clutch pack, it cannot transfer 100% of the engine's torque;

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?

The important bit-the coupler. Note, I haven't yet put a multimeter on the actuator to find out whether it's a variable coupling (as would be evidenced by variable voltage between 0-14.4v) or a simple on/off (as would be evidenced by either 0 or 14.4v)

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.