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ADC - How does it work??

48K views 17 replies 9 participants last post by  SailorGriz 
#1 ·
Hi All,

Was doing some more looking @ the 550XP Non EPS, and wonder how exactly the ADC (active descent control) actually works?

Is it linked to the ending braking?
 
#2 ·
there is a unit if the front drive that does all the work the circled part is it
 
#3 ·
please correct me if im wrong
 
#4 ·
2009 Polaris Sportsman X2 800 EFI Owners Manual said:
Active Descent Control (ADC) System
The ADC system allows engine braking to all four wheels when the
vehicle descends a hill or incline. Always move the 4X4 switch to ADC
4X4 before ascending or descending a hill.
That's right from my manual.
 
#6 ·
copied from another site.

Operation
Engine Front Gearcase: Active Descent Control (ADC) is controlled by the ECU and will enable when only the following conditions are met:
* Vehicle is below 15 mph (24Kph)
* Throttle position sensor (TPS) is at idle position
* The AWD switch is switched to 'AWD' or ADC

Once the conditions are met for engagement, ADC remains engaged as long as conditions are met.
With the AWD switch off, the vehicle drives only the rear wheels (2 wheel drive). When the AWD switch is 'ON' the magnetic coils are active, the AWD coil indexes the clutch mechanism so that both front axles will engage when there is a loss of rear wheel traction. In addition to the rear wheel engine braking, the ADC coil provides front wheel engine braking at speeds less then 15 MPH (24Kph) with the TPS at idle position.

ADC Engagement:
When the AWD switch is activated, a 12 volt dc current is present at the input shaft coil(1). Operation is controlled by the ECU grounding and ungrounding the coil.The coils magnetic field attracts a splined armature plate (2) on the pinion (input) shaft. (4). The energised splined armature plate attracts the unsplined eccentric cam(3), which begins to turn with the input shaft. The eccentric cam drives a hydraulic piston/pump assembly (5). The pressure created by the pump assembly forces fluid through passages to the piston assemblies (6) located in each case half. Hydraulic pressure forces the piston assemblies inward to compress the splined clutch packs (7) forming a dynamic coupling to each front drive axle, resulting in true all-wheel EBS operation upon deceleration.

It does not operate the brakes.
 
#9 ·
OK, so I'd like to be able to engage AWD and KEEP it engaged--not have it only engage when the rear wheels spin. Would it be possible to run a secondary ground to the input shaft coil and manually activate the coil with an auxiliary switch? Or, better yet, use the ADC switch to manually activate the coil instead of running it through the ECU?
 
#7 ·
How does it work?

Flip the switch to ADC, let it go down the hill, the you won't be able to see the bottom until you start down hill(steep), place your feet on the front fenders cause it feels like you will go over the bars, OH is that my cell phone ringing, Ya EPS too, Talk and steer at the same time while creeping down the hill. ( is there a hand free law on a ATV?) The ADC is one of my Favorite features on the XP. It works Great!!
 
#8 ·
lol



ya going 2mph down a hill without touching a single thing is sweet and impressive
 
#11 ·
Thanks AmdForever. Of course one wouldn't want to drive around in full lockup--any more than I did with my Yamaha or my Kawi. BUT . . . it locks it up in ADC and reverse so the stress must be within the design limits of the unit.

The moment of maximum traction for the back tires is BEFORE they slip, not after. So, if the front won't engage until after the back slips it's not possible to get the full traction capability of the machine.

Is it enough to make a difference in the Real World? Beats me. But I do know that I was driving down a very slick, muddy, rutted road and tried to turn a bit to climb out of the ruts. The front end just slipped sideways and wouldn't climb out--until I goosed it a bit and slipped the rear so the front had power. The driven front wheels climbed right out of the rut. Seems silly to not be able to drive the front without slipping the rear.

Again, in the Real World it may not matter. At least, not very often. But it still seems like the machine is designed to have less than it's maximum potential.
 
#13 ·
Nope, no way to make it engage full time. I agree that there are times when it would be nice, such as most any off camber, slick trail condition, but 95% of the time it is pretty much a perfect setup.
 
#16 ·
I was looking at the exploded diagrams of the front diff and reading about how it works. In AWD there appears to be what amounts to a one-way clutching mechanism. It free wheels the front until the back slips ever so little then engages as long as the torque remains on the "clutch." So, lockup should be virtually instantaneous, maybe even before the wheels actually lose traction.

In reverse the "one way" feature of that device is operated in reverse--which mechanically locks up the front end. So, no way to use the reverse lockup feature for true "lock up."

The ADC is, indeed, a completely separate system. I can't tell if locking that system by "defeating" the ADC would work when driving the system forward or if it only works when braking the system to slow it down--as it's designed to do. So, I can't tell if defeating the ADC to make it a full lock up would work, or not.

I guess in the long run it doesn't much matter. It certainly works well the way it's designed! Just seems silly to not have the ability to make it lock up on command. JMHO.

Thanks for all the responses! Maybe someone at Polaris will read this and decide it'd be a nice feature for future models--or come up with a mod for our current Sportsmans. Sportsmen? Hmmmm . . . . :hmmm:
 
#17 ·
The ADC is, indeed, a completely separate system. I can't tell if locking that system by "defeating" the ADC would work when driving the system forward or if it only works when braking the system to slow it down--as it's designed to do. So, I can't tell if defeating the ADC to make it a full lock up would work, or not.
I'm sure you could in-fact defeat the ADC, but I would question how stout the clutch packs are since they are designed to just lock the fronts together going downhill slowly. No extreme abuse is occurring there. I would also be questioning how long it could stay energized, pressurizing the system with fluid til it potentially boils.
 
#18 ·
Good points, AmdForever!

I just got back to the Farm yesterday and rode out to check some drainage problem areas as the snow is melting. Crossed a couple of ditches I wasn't so sure I'd get out of without help--narrow, deep, soft bottom. Fact is, with one exception in very deep snow (two weeks ago), this 550 has gone everywhere I've pointed it and had no problems getting through it all.

I still think it's silly not to be able to lock it up and keep it looked up--but I also don't think there's any real need to ever actually do so which means it doesn't really matter. IMHO.

Guess I'll stop ==> :deadhorse: and just :veryhappy: 'cause it goes where I tell it to!
 
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