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The DynaMax AWD coupling is basically like some others in that an electric motor operates an oil pump to pressurize a housing with a multidisc clutch. The hydraulic pressure applies the clutch so required torque is transferred from the front-drive-based system to the rear differential—the greater the pressure, the more torque is shifted to the rear.

However, there are numerous differences vs. other systems, both within the coupling and with the high level of active control that speeds response, to improve overall performance.

First, the CAN bus (Controller Area Network) monitors signals, principally throttle position, steering angle, vehicle speed, and road texture (an algorithm that includes wheel speed sensor signals). The signals go to the AWD computer, which calculates the ideal front-rear torque split that it anticipates.

The computer then operates the motor at up to 10 rpm to run the pump, to build up the required hydraulic pressure (maximum of 320 psi/2.0 MPa) for the clutch. This is accomplished with the aid of a feedback signal from a pressure sensor on the clutch housing. The motor stops when the correct clutch-apply pressure is reached.

At start-up the system presets the front-rear torque distribution so there is no slip on the front axle. As the vehicle moves down the road, the DynaMax computer continuously monitors sensor readings, to anticipate changes in upcoming driving conditions.

The computer recalculates impending torque split requirements from the CAN bus data and, if necessary, makes instantaneous adjustments in motor-pump-to-clutch-housing system oil pressure with the help of the housing pressure sensor.

Because Magna engineers designed the DynaMax system to react quickly in changing traction conditions, such as encountering an icy road patch, it never starts from an "off" position.

If the pressure must be increased (for more torque transfer to the rear), the motor turns forward to operate the pump. If the front-end traction is good, the computer simply backs off the motor-pump assembly to reduce clutch-apply pressure. Then more torque (and if it's appropriate, all the torque) is delivered to the front wheels. There are no pump valves to open and close.

The pump is a gerotor type. Engineers note that its tight internal tolerances enable it to maintain commanded pressure for a short duration, as effectively as a plunger- or valve-type pump. If the time period for steady state becomes extended, so that leakage starts to reduce the apply pressure, the pump runs to reload the hydraulic circuit as required.

As a result, the DynaMax computer's typical response time to "tune" for an impending change in torque-split requirement is 50-100 ms. If a torque increase is needed from the engine, it takes up to 300 ms to build up, observed Walter Sackl, Magna Powertrain's global product manager, so in some cases the engine may determine the actual time period.

In any event, the response of the DynaMax itself should occur well within 150 ms, Sackl said.

The computer algorithm for the clutch looks for consistently good front-end traction and when possible will maintain 100% to the front wheels for fuel economy. The algorithm, however, is adaptive; in "sporty driving" it will apportion torque as needed between front and rear, Sackl said, and it will transfer 100% to the rear if appropriate.

The up-to-100% front-or-rear torque split, in conjunction with the AWD computer's active control approach, also minimizes oversteer and understeer in normal driving situations, he added. In addition, the system has a manual-select position for a 50-50 torque split.

The DynaMax coupling was sized for light weight and engineered for minimum energy use. Its 727 lb·ft (1000 N·m) peak torque design capacity is more than adequate, even with a generous safety margin, because the new Sportage's 2.4 L engine's rated peak torque is 168 lb·ft (228 N·m). However, Kia intends to use this coupling in forthcoming vehicles.

The Sportage has a tow capacity of 2000 lb (907 kg); Kia's testing showed that even with maximum loads, including hill climbing, the coupling's internal temperature never reached a thermal shutoff level. A contributing factor is the cooling provided by the large oil capacity of the DynaMax housing, Sackl said.

The fluid fill, unlike competitive designs, is life of vehicle, he added.

Kia has an exclusive arrangement with Magna Powertrain that with required competitive development times should last for two model years. The DynaMax coupling is being built in Korea in a plant that is a joint venture between Magna Powertrain and Hyundai WIA, a parts manufacturing affiliate.
Magna's new AWD system powers 2011 Kia Sportage - SAE International
 

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Discussion Starter #3
I found some more juicy details on our proactive DynaMax AWD trans today. Although this piece was on the 2011 Sportage but it should apply to us as well.

2011 Kia Sportage's Proactive All-Wheel Drive System | National Post

Unlike many of its peers, the Sportage arrives with a proactive all-wheel-drive system. Many of the Sportage’s rivals feature the usual slip-first-grip-later (reactive) system. The problem with this strategy is that the car must go out of control (unwanted wheelspin) before it is brought under control (the all-wheel-drive system begins to reapportion the drive torque). In the worst case, if the car is understeering and the system reads this as wheelspin, it sends power rearward at the wrong time–the power transfer drives the car further into understeer. The sudden realization that the driver has lost the car is an unwelcome pucker moment at the best of times. The reason for the limited ability is that these reactive systems only monitor wheel speed, which means the front wheels must slip before the system picks up on the problem.

The Sportage’s new Dynamax all-wheel-drive system monitors both wheel speed and accelerator pedal input. If the system “sees” the driver tromp on the gas when vehicle speed is low, it knows that wheelspin is inevitable. Rather than waiting for the Sportage to lose traction, the system begins to close its electrohydraulically controlled multi-plate clutch, which reapportions the drive torque before the problem arises. The fact its action is proactive puts it in lofty company — Subaru and Audi are both revered for their proactive AWD systems.

The Sportage has a lock mode for those times when the going gets really slippery. The driver simply punches a button and the system locks the clutch, which splits the power evenly (50/50) front to rear. However, if the vehicle exceeds 30 kilometres an hour, the system automatically unlocks and returns to its proactive mode. This is done for handling considerations — trying to negotiate a fast corner with the centre clutch locked is not the smartest idea. The instant the vehicle drops back below the 30-km/h threshold, the system returns to its locked position.

The use of the lock mode could lead to an unwanted side effect during full-lock turns — it’s called crow hopping and is caused by drivetrain windup. To counter this negative effect, the Dynamax system looks at steering angle. The instant it sees a full-lock turn, it releases the clutch, which eliminates the potential windup. As soon as the driver begins to straighten the steering, the system resumes its locked duties.

This basic ability is layered with a good electronic stability/ traction control system. It is the traction side that’s used to control the Sportage’s power split left to right. If the right wheel begins to slip, the traction control brakes that wheel, which forces the drive to the wheel (left) with traction.

The second bit of the advanced equation is the ability to turn the front wheels and use this action as a level of electronic stability control. In simple terms, the system monitors driver input and compares it with the vehicle’s reaction. If the Sportage begins to oversteer, the steering side of the stability control system does what all good drivers would — steer into the skid. In this instant, it’s the electric motor that provides the power assist that turns the front wheels into the skid. It only turns them in by three or so degrees, but this is enough to help the regular electronic stability control system regain control in a more timely manner. The steering action is such that the driver is unaware of its helping hand — there’s no tugging at the steering wheel at all.

The system also turns the wheels during a hard stop when the left and right wheels are riding on different surfaces. Under normal circumstances, even with the anti-lock braking system doing its thing, any car will pull to the right when the right wheels are on tarmac and the left wheels are on ice or snow. Turning the front wheels to the left by just a couple of degrees counters the brake pull, which keeps the car in a straight line. Simple.

Obviously, if the car is in an understeer condition, turning the wheels only worsens a bad situation. Here the system ramps up the assist level so that when the front wheels do find some grip and the driver reefs on the steering wheel to avoid a house or tree, it requires much less effort. Few cars offer this level of technology regardless of vehicle cost.

Beyond these two significant pluses, the Sportage has a roll mitigation system that triggers the seat belt pretensioners and side curtain air bags when the car is in the final throes of flipping over — this keeps the shattered side window glass out of the cabin and the occupants inside. Then there are the semi-active shock absorbers — amplitude-selective damping in tech-talk. If the speed of the body’s motion is slow, the shocks deliver soft damping characteristics. When the body motion reaches a certain speed (hence the amplitude in the name), the damping automatically switches to a firmer setting by altering the internal valving. This controls unwanted body roll and brings much less nose dive under hard braking. It is a simple system that brings many of the benefits of a fully active damper system, but at considerably less cost.
 

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below is taken from the initial post :

"The computer algorithm for the clutch looks for consistently good front-end traction and when possible will maintain 100% to the front wheels for fuel economy. The algorithm, however, is adaptive; in "sporty driving" it will apportion torque as needed between front and rear, Sackl said, and it will transfer 100% to the rear if appropriate.

The up-to-100% front-or-rear torque split, in conjunction with the AWD computer's active control approach, also minimizes oversteer and understeer in normal driving situations, he added. In addition, the system has a manual-select position for a 50-50 torque split."

Wasn't aware that the SFS AWD could be 100% RWD drive .
 

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We got a nice snow storm yesterday and I was able to test the AWD system on the 2017, and it's quite good IMO.

Pulls straight ahead, works fine. No complaints.

When driving low speed in lots of slippery snow, I noticed that the traction control cuts the power too much too fast, and you have trouble moving forward. (which is appropriate when driving at higher speeds on an icy road, you don't want to allow wheel slipping).
Turning off traction control fixed that, but I prefer to keep TC on, but with a more "relaxed" mode.

It seemed to me that when engaging the 4wd lock, the traction control allows a lot more wheel slippage, does not cut engine power as much, and you get through easier.
That looks like the solution.

Will need to try it out more in a parking lot when it snows again, but it seems that the 4wd lock switch also changes the rules of the traction control and allows wheel slip to "get out of a slippery situation at low speed". It's not "just" a 50/50 split of torque.

Opinions?
 

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Discussion Starter #7 (Edited)
When driving low speed in lots of slippery snow, I noticed that the traction control cuts the power too much too fast, and you have trouble moving forward.
I also experience something similar, but in the rain going uphill:
http://www.hyundai-forums.com/dm-2013-santa-fe/520657-awd-rain-traction-control-steals-fun.html

I think traction control and AWD seem to contradict each other in terms of what each system want the wheels to behave, so it's interesting to find out more on when traction control would kick in, in place of sending torque to the rear wheel to overcome the slippage. Having said that, since Dynamax seems to be the a proactive system, I wonder if traction control kicks in After it has sent power to the rear wheel but you're still slipping, and therefore traction control kicks it and basically say "RELAX, slow down..." to the driver?

Glad to know having it locked 50/50 helps. I guess it needs to ease off the traction control if it was designed to be used on low traction surfaces to begin with.
 

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I have rarely ever had the traction control kick in despite our ugly winters, and I climb a lot of steep grades and did some standing start tests on those grades when the vehicle was new. The wild card of course is always the tires. They are what makes contact with the road surface and every other system responds according to that level of traction. The tires on like vehicles may be much different. My SFS and Continental tires that I like and that have performed very well on other vehicles that we have owned and my wife's SF long have the Kuhmos or whatever the heck they are that I have typically found to be a lower winter traction tire. The difference can be amazing. I have driven GM models with brand "A" tires that were great in the snow. Jump into a different trim scale of that same model and year of vehicle with brand "B" tires and the identical vehicle (Other than tires) handles horribly in the snow.

Thus do keep in mind as you compare note that like vehicle will respond differently based upon both the brand and model of tire installed. Tire pressure cal also make a difference but should always be set per the vehicle's placard or owner's manual.
 

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I have nokian hakkapelita 8 SUV studded tires, best in the world.

BTW, I tested today with the 4wd lock switch, and TC kicks in as fast.

Only option to go through piles of soft snow at low speed is really to disable TC. Then it works fine.

I miss the jeep grand cherokee for the drive modes. That was really awesome.

Auto let you do some safe powerslides across the street when turning left. It just gave enough to powerslide but not loose control.
Snow mode was a VERY safe 50/50 that would not let you slip (high speed slippery roads).
MUD mode was VERY good for deep snow, engaged all 4 wheels and gave it just enough slip but not too much.

I miss the GC, but a 2017 summit is 20K CAD more than the SFS and was simply out of my budget, and I wanted to get a new car, have a 5y warranty, and not bother with any repairs.

Maybe one day when I'm richer.
 

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Thanks! I wonder how Dynamax's system performs vs Mazda's i-ACTIV. They are both "On-Demand Twin Rear-Axle Couplings" and they both claim to be proactive.

Snow Testing Mazda?s i-ACTIV All-Wheel Drive » AutoGuide.com News

I see Hyundai using what C and D calls " on demand coupling" with an open diff in the front. The article mentions this is what is in the CX-5 . The other twin rear axle coupling provides for what some call true torque vectoring - more expensive setup.

Don't know how much of the AWD programming Hyundai does but wouldn't be much surprised if this is done by Magna.
 

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the 2017 SFS system works pretty well on the snow and ice we got here this winter I would say.

It's more on the safe side, and less on the fun side, but it's a family safe suv, and it's very safe on icy roads.
Easily moves through snow and ice, always well balanced. No bad comments.
 

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just tested it in some 6 inches of slush at around 0 celcius, very slippery (on wet/icy grass).

I was able to get through with no drama, but it had to work, slip,brake, etc etc to get through.

It did fine I guess, but it's definitely not a grand cherokee with the quadra-drive where as soon as you get any slip, the rear ESLD locks and then it just rams you forward with no stopping.
The jeep felt unstoppable. Not getting that feel in the SFS, but so far it has never left me stuck, so I can't complain.
It looks like it will get you there, with a tad more drama.
 

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Much more robust and capable systems offered in Jeep models, the C & D link to awd system mentions JGC Laredo using an open differential, that would be somewhat comparable to the SFS in that it also employs brake lock differential thru the traction control systems , but as you know the Quadra Trac systems are a step up with ELSD and multiple drive modes.

The Magna system in the SFS is designed largely for front wheel drive use and limited (as needed) use in the AWD mode, I think if someone drives one extensively where the AWD mode is used the drive train may well show the strain, whereas the JGC is more heavy duty in design. I took my SFS up a rocky dirt road in CO that had high clearance warnings and I did get hung up several times but the AWD worked quite well - however that type of off road driving is clearly not what the vehicle is intended to be used for and I'm not about to go down that road again.

The you tube video by the mfg are IMO informational to a degree and sometimes even amusing in how they bias the info, if you compare a JGC AWD V6 with a SFS AWD 2.0T the SFS is I think larger in dimensions but nearly 1k lighter - a good amount of the difference is in the heavier and more robust Jeep drive train and suspension , but compare the fuel economy ratings and they are very similar.

But I think you get above $ 45k when you start putting the higher level AWD systems into the Grand Cherokee so for it's intended use the Magna system I think functions very well and this type of design is what many AWD systems use these days.
 

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Well said Dtech. We have had owners in the past that had to drive for one or more miles on roads that were not maintained during the winter (Not plowed) or that had ridiculously long driveways (Perhaps up to a mile long) because they wanted their home to be isolated from the neighbors and the (GM) AWD systems were not up to their expectations. They really needed a true 4WD vehicle or at the very least something more than the part time systems that GM offers. GM vehicles also do not offer the differential locking feature and I do find that to be very useful in urban driving in deep snow or very slippery conditions. Know that you truly need and purchase accordingly.
 
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