Abls

shleprock · 06-30-2004, 04:20 PM

I have a XE KingCab4x4..Was wondering how that ACTIVEBRAKELIMITEDSLIP Worked??from what i understand it applys the brakes the the wheels that are slipping and applys power to the wheel thats not?...If I put it in 4x4 I guess it does the same thing on the front diff?..Computer controled?was just wondering exactly how it worked.For example say I was stuck in a snow bank and my back 2 wheels was spinning? would both my front wheels grip? in 4x4 mode HI..

ATitan4Me · 06-30-2004, 04:25 PM

They way that it works is when the computer sees more speed from your rear wheels than the front it applies the rear brakes untill the slippage is stopped. It works the same in 4hi, but is disabled in 4lo. The computer never applies front brakes only rear. It can be slightly defeated by turning off the VDC via the switch on the dash.

shleprock · 06-30-2004, 04:32 PM

Quote:

Originally Posted by ATitan4Me

They way that it works is when the computer sees more speed from your rear wheels than the front it applies the rear brakes untill the slippage is stopped. It works the same in 4hi, but is disabled in 4lo. The computer never applies front brakes only rear. It can be slightly defeated by turning off the VDC via the switch on the dash.

Dont have that switch....guess i have a open frontend in 4Hi

bwalkertitan · 07-01-2004, 02:08 AM

Quote:

Originally Posted by ATitan4Me

They way that it works is when the computer sees more speed from your rear wheels than the front it applies the rear brakes untill the slippage is stopped. It works the same in 4hi, but is disabled in 4lo. The computer never applies front brakes only rear. It can be slightly defeated by turning off the VDC via the switch on the dash.

I believe this is misinformation - from what I understand, it can work on all four wheels on a 4x4 and it is still active when in 4Lo although the VDC is not.

When the VDC is off, the ABLS is still operational (this is clearly stated in the owners manual).

IMADOGMAN · 07-01-2004, 06:42 AM

If you have an E-locker, you won't have a VDC switch, because you won't have VDC, just ABLS

bwalkertitan · 07-01-2004, 09:19 AM

Quote:

Originally Posted by IMADOGMAN

If you have an E-locker, you won't have a VDC switch, because you won't have VDC, just ALBS (not ABLS)

Yes my statement applies to the 4x4 model with VDC and without e-locker, although I presume in 4x4 models with e-locker that the front ABLS system is still operational in 4Lo.

Another bit of misinformation, it is called ABLS which stands for Active Brake Limited-slip (take a look at the manual or go to the Nissan website)

IMADOGMAN · 07-01-2004, 04:18 PM

Quote:

Originally Posted by bwalkertitan

Yes my statement applies to the 4x4 model with VDC and without e-locker, although I presume in 4x4 models with e-locker that the front ABLS system is still operational in 4Lo.

Another bit of misinformation, it is called ABLS which stands for Active Brake Limited-slip (take a look at the manual or go to the Nissan website)

Bwalker...I realized that I had a brain cramp, and was going to edit my post regarding my mistake with the acronym, but you got to me first.

Now it is my turn to point out some misinformation, unless the owner’s manual is wrong, or I missed something….You said that the owner's manual "clearly stated" that the ABLS still operated when the VDC switch was turned off. I couldn't find that...here is what I found...let me know if I missed something.

From the owner’s manual…

The VDC system uses an Active Brake Limited
Slip (ABLS) system to improve vehicle traction.
The ABLS system works when one of the driving
wheels is spinning on a slippery surface. The
ABLS system brakes the spinning wheel which
distributes the driving power to the other drive
wheel. If the vehicle is operated with the vehicle
dynamic control system off using the VDC OFF
switch, all VDC and ABLS functions will be
turned off.

The ABS will still operate with the VDC
system off. If the ABLS system is activated, the
slip indicator light will blink and you may hear a
clunk noise and/or feel a pulsation in the brake
pedal. This is normal.
While the VDC system is operating, you may feel
a pulsation in the brake pedal and hear a noise or
vibration from under the hood. This is normal and
indicates that the VDC system is working properly.
The computer has a built in diagnostic feature
that tests the system each time you start the
engine and move the vehicle forward or in reverse
at a slow speed. When the self-test occurs, you
may hear a clunk noise and/or feel a pulsation in
the brake pedal. This is normal and is not an
indication of a malfunction.

Me again:
It seems that the "ABS" Anti-Lock Braking System still works when VDC is off, not the ABLS

As for the ABLS, I don't think that it cares if you are in 4HI or 4LO.

I am guessing here, but I think that it only senses slippage from left to right, not front to rear, but it might monitor tire slippage all around, and apply braking to the tire that is slipping in comparison to the others.

I can only guess that the E-locker messes up the VDC, so that it won't work properly. The ABLS will never see any slippage (left to right) on the rear of the E-locker when it is locked, so it probably doesn't matter to that system. When the E-locker is not locked, it would sense the slippage and apply the brake, just like with a regular differential. Anyone correct me if you know otherwise.
Thanks,
Dave

Austin · 07-01-2004, 05:30 PM

ABS still works when VDC is disabled.
ABLS still works when VDC is disabled.

ABLS functions in both 2hi, 4hi and 4lo. If you have the rear end locked, ABLS is effectively disabled for the rear only (obviously) as there can be no differential movement between left rear and right rear. ABLS still functions for the front end with the rear end locked.

ABLS acts to limit wheel slippage in side to side relation, not front to rear.
Example: Truck is in 4hi, right front wheel (only) has no traction. ABLS will apply brake force to that wheel only to transfer torque to the left front wheel. The rear wheels are not affected in this example.

Here is something I posted in an earlier thread:

To say it more precisely, an open differential will deliver equal amounts of torque to both sides.

This means it's important to understand torque - torque is a twisting or turning force.

For torque to be generated, there must be something to push against. If there is no resistance to turning a wheel, then very little torque is generated to turn the wheel - effectively none. With an open differential, the equal amount of torque is applied to the other wheel - effectively none.

That means that when one wheel leaves the ground or is in a zero traction situation, that wheel requires effectively zero torque to turn it. An open differential delivers exactly that amount of torque - effectively none - and it delivers that amount of torque to both sides.

Remember, to generate torque, there must be some resistance to turning or twisting.

Active Brake Limited Slip simply gives the open differential something to push against. When one wheel leaves the ground or is in a zero traction situation and begins to spin, ABLS will act to apply brake force to that wheel and that wheel only. To the open differential, this has the same effect as having traction with that wheel - there is now something to push against, allowing torque to be produced and delivered equally to both wheels.

Most reports of ABLS I've read indicate it works as designed. If, in fact, it *does* work as designed, it's the neatest thing since sliced bread. The driveability and low maintenance of an open differential with the traction of a limited slip differential. You get to have your cake and eat it, too.

That's how ABLS and open differentials work.

VDC is the system responsible for reducing engine output to limit wheelspin.

When you mash the gas and one rear wheel begins to spin (begins to lose traction), ABLS acts to apply brake force to that wheel - allowing the open differential to generate torque and be delivered equally to both wheels - giving torque back to the wheel with traction.

At this point, if both wheels spin and VDC is turned on, VDC will act to reduce engine output to reduce wheel spin. If VDC is turned off, you'll sit and spin both rear wheels.

Austin · 07-01-2004, 05:38 PM

Here's another something I posted in an earlier thread:

Quote:

Originally Posted by Bluto

I don't like the thought of having the brakes work against the engine.

The brakes aren't working against the engine. They're working *with* the differential.

Quote:

Originally Posted by Bluto

Brakes aren't designed to clamp and transfer torque, especially 380 ft-lbs. The brakes will lose. They are for stopping vehicles.

The brakes will definitely not lose. They are specifically designed to clamp, which, due to their mounting location, means they're specifically designed to stop rotation of the tire/wheel. Without ABS, you'd be able to lock up the wheels anytime you wanted to. Brakes that size have the clamping force necessary.

You're correct in saying that the braking system is not designed to transfer torque... but that's not what's happening. The braking system (as it's used by ABLS) simply gives the wheel some resistance to turning - allowing torque to be generated - and that allows the open differential to deliver torque to the other side.

Take an extreme case - right rear wheel up in the air spinning free, left rear wheel on the ground. RR wheel has zero traction (there is nothing for it to push against), therefore, due to the open differential, zero torque is generated in the rear.

Thanks to the open differential and one wheel having zero traction, the truck is stuck.

Enter ABLS.

ABLS clamps the RR brake caliper shut (it'll never actually go this far - I'm just giving an extreme example). The RR wheel now has effectively infinite traction - allowing infinite torque to be generated and distributed equally to both sides. This allows the torque necessary to move the truck to be delivered to the LR wheel. Truck not stuck.

IMADOGMAN · 07-01-2004, 05:40 PM

[quote=Austin]ABS still works when VDC is disabled.
ABLS still works when VDC is disabled.

From the owner's manual...
If the vehicle is operated with the vehicle
dynamic control system off using the VDC OFF
switch, all VDC and ABLS functions will be
turned off.

Who should I believe?

bwalkertitan · 07-01-2004, 06:57 PM

Quote:

If the ABLS system is activated, the
slip indicator light will blink and you may hear a
clunk noise and/or feel a pulsation in the brake
pedal. This is normal.

Ok IMADOGMAN - I just went and checked it with my own truck, so you can believe me. I turned off the VDC and while taking a corner mashed the gas pedal to see if the SLIP light would illuminate (from the above statement, that would identify the ABLS being active). It did illuminate with the VDC off, so it was active (It also made a big burn out - with increasing power until I let off the gas).

If I mash it with the VDC on, the SLIP light comes on, but the VDC limits power and the slide burnout stops.

bwalkertitan · 07-01-2004, 07:16 PM

Oh and here is what my owner manual says verbatim from page 5-29.

"If the vehicle is operated with the vehicle dynamic control system off using the VDC OFF switch, all VDC and TCS (traction control system) functions will be turned off. The ABLS and ABS will still operate with the VDC system OFF. If the ABLS system is activated the slip indicator light will blink and you may..."

SO in actuality, believe me (because I just tested it per above post) and believe the manual which clearly states that the ABLS is functional when the VDC is off.

IMADOGMAN · 07-01-2004, 10:14 PM

Hey Bwalker, I have to agree with you. My manual says the same thing as yours. Sorry for the confusion, but the Titan manual that is Online at [www.nissan-techinfo.com] has completely different wording. I have included it below. Maybe Nissan should update their online information.

Silly of me to think that they would match.

Copied from the ONLINE manual: pg 5-29

The VDC system uses an Active Brake Limited
Slip (ABLS) system to improve vehicle traction.
The ABLS system works when one of the driving
wheels is spinning on a slippery surface. The
ABLS system brakes the spinning wheel which
distributes the driving power to the other drive
wheel. If the vehicle is operated with the vehicle
dynamic control system off using the VDC OFF
switch, all VDC and ABLS functions will be
turned off. The ABS will still operate with the VDC
system off. If the ABLS system is activated, the
slip indicator light will blink and you may hear a
clunk noise and/or feel a pulsation in the brake
pedal. This is normal.
While the VDC system is operating, you may feel
a pulsation in the brake pedal and hear a noise or
vibration from under the hood. This is normal and
indicates that the VDC system is working properly.
The computer has a built in diagnostic feature
that tests the system each time you start the
engine and move the vehicle forward or in reverse
at a slow speed. When the self-test occurs, you
may hear a clunk noise and/or feel a pulsation in
the brake pedal. This is normal and is not an
indication of a malfunction.
5-29

Me again:
It seems to have been rewritten...if only to confuse....

Oh well, not the first time I have been fooled...

bwalkertitan · 07-01-2004, 10:59 PM

Not fooled..no biggie...i just knew i had read it and knew I had experienced it - that was why i kept posting. Definitely strange that the online manual has different wording. I guess the person that did the online manual was being lazy. lol.

IMADOGMAN · 07-02-2004, 06:04 AM

bwalkerTitan,
I am glad that you stayed with it. I would rather have the facts. I just didn't expect to get misinformation from Nissan.
Thanks,
Dave