So I was reading an old thread from the roadie on the other site, lamenting how H3's have electronic gizmos that brake individual wheels so that lockers and disconnects aren't so necessary, and I remembered something from my sport compact days... LINE LOCKS do the same thing! So I propose a question to the group here:
Is there any reason that installing 4 line locks, one on each wheel, wouldn't work to provide sufficient torque on any wheel needing it?
while I wait for responses.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
Right... but doesn't it require that you press the brakes, then apply the line lock, then release the brakes, so as to keep the hydraulic pressure on the activated line-locked corner?
It would be a very tedious process... but it could be helpful. I'd reccommend not installing it on all 4 corners. Since we have a locked T/C, all you would need to do is lock the one spinning rear wheel. Then the free side would receive all of the power. Might not be a good idea with the front. Not sure if the diff would like it much as you'll be transfering the power by spinning the spider gears at high speed... they're really only meant for minimal rotation and for transferring forces without much rotation.
It's one of the top ten electronic gizmos I thought I could design and sell. Same idea as traction control, but you just have to hack into the ABS lock/purge valves. That would work for the front, if you have one spinning tire. In the rear on 2002-2005 before traction control, there is only one ABS channel for both rear wheels, so that won't work. Then you have to do it mechanically on the Ebrake cables. Those are separate left/right after the tie-together point in front of the differential.
Was on my hot list until I continued to hit the trails, and concluded - there are very few trails I am thwarted on by lack of traction. Ground clearance and insufficient armor problems deny me a lot more.
You have to try hard trails and back down from them a LOT to build up the priority table of what mods will allow you to go where.
What the rock crawlers call the line lock concept is "cutting brakes". Run a search for that.
The guy who did my rock sliders also worked on this Red Bull buggy, on the hydraulic and electrical system, including the cutting brakes. I met Dustin Webster a couple of times and got a good tutorial.
Quite the valid idea, but there would need to be some modifications in order to have it be useful in real time situations. Perhaps some kind of electronic actuated e-brake on each rear wheel, to be operated with momentary switches..
The Roadie wrote:It's one of the top ten electronic gizmos I thought I could design and sell. Same idea as traction control, but you just have to hack into the ABS lock/purge valves. That would work for the front, if you have one spinning tire. In the rear on 2002-2005 before traction control, there is only one ABS channel for both rear wheels, so that won't work. Then you have to do it mechanically on the Ebrake cables. Those are separate left/right after the tie-together point in front of the differential.
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Good thing I have the newfangled 2-channel ABS on the rear, huh? Now to work on hacking into the ABS system... I actually know a guy.... And does the design of the ABS system allow you to brake individual wheels? If so, then I might be able to go somewhere with this.
Gordinho80 wrote:
HAHAHA But if you'd like an explanation, I'd be happy to give you one.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
Go, Philberto, the audience is listening. I don't know if this idea is warranted on vehicles such as ours, but a detailed explanation of concept and real world worth would be a great learning tool for the rest of us.
Well okay, most of us know that during offroad driving, we can encounter situations where we have one or two wheels off the ground, usually one per axle (hopefully). We can also encounter situations where perhaps up to 3 wheels don't have traction. When these situations arise, we want the power to go to the wheels on the ground, with good traction, rather than the wheels in the air or on the super-slick mud patch.
Now for some of us, we have the g80 option in the rear, a limited slip differential that automatically engages and transfers power from the spinning wheel to the wheel with traction. This option is very valuable for those of us who see very difficult trails, especially on hills in low-traction situations.
However, some of us don't have that RPO on our trucks (like me) and minimum cost to swap a rear axle is $435 plus any tools/lubricants, etc. Even if you have the rear g80, there is currently no easy or affordable way for us to get a front locker, which would allow the front wheels to do the same thing.
In an open differential, which any non-g80 truck has, when one tire has less traction than the other one, that tire will usually spin uselessly while the other tire does nothing. Light braking while using the gas is a technique that has been used many times to transfer some power back to the tire with traction.
On many modern pseudo-offroad cars (i.e. Porsche Cayenne) that do not have lockers, a form of individual wheel braking is used. When a wheel loses traction, the electronics in the car automatically apply the brakes on that wheel, causing the differential to transfer power to the other wheel on the axle, as it's now easier to drive that wheel. This is done by monitoring wheel speed sensors to determine if one wheel is spinning significantly faster than the other. If so, then the brakes apply, power is transferred, and the car moves forward. Here's a youtube video of this happening on a Cayenne, so that you can see how the wheel will spin, then slow down as braking force is applied:
The advantages of this are fairly clear, though I will have to look into the front differential issue that James brought up. It allows us some semblance of front lockers, probably enough that we won't need them, and it allows those of us with open rear diffs an upgrade path that (on 06+ models) might only require some software reprogramming. As far as whether this is warranted on our vehicles, when you think that our vehicles were originally designed as soccer mom/towing vehicles, and the other vehicles that have this system are similarly designed (Once again, remember the Cayenne!), then adding this kind of system makes perfect sense. The main challenge stems from being able to modify the computer that controls the ABS and traction control to allow it to do this.
/end lesson
-Phil
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
The simplest system that could be utilized would be simple line locks controlled manually. Beyond that, I have a lot of research to do, and I very much doubt that any GM product outside of the hummer line would have anything useful for us. The systems are very recent, and GM as of recent has been somewhat... neglectful..... in the offroad department. As far as whether the software issue is beatable, it depends on how deep into the programming I can get, and I might be able to utilize aspects of the traction control and stabilitrac programs to come up with an "offroad traction control." I'll have to borrow a tech2 and see what I can come up with, because honestly this whole process will be a learning experience. Working for a dealership, I am in a unique position to modify things and get questions answered, and I invite anybody else who might know engineers or designers working for GM to get in on this as well.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
In line with my new project, is there anybody who can tell me if our ABS has the capability of individual braking (06+) and if the EBCM is what I should be looking to reprogram? I'd like to have a little bit of info before I go and ask the people I know. Also useful to me would be a source for a factory service manual and any other documentation I can get on the ABS, EBCM, and Traction control/stabilitrac systems.
I'm planning on trying to model an "offroad traction control" system after VW's Electronic Differential Lock system that engages brakes on any wheel doing 100rpm more than its neighbor. We'll see if I break any parts doing it, but hopefully everything will work out.
Taken from VW site:
"Electronic differential lock, or EDS (german acronym for same), is not a differential lock as per usual. It uses the ABS sensors at driven wheels (i.e. left/right front on FWD, left/right front and left/right rear on quattro), to determine if one of the two wheels is spinning faster than the other. At some speed differential (approximately 25 mph / 40 km/h), the highly sophisticated fifth-generation ABS/EBV actually pulsates the brake momentarily at the spinning wheel, effectively transferring the torque through the open differential to the wheel with more traction. This system is effective, but due to the stress that it would create on the braking system, it is only used up to speeds of about 25 mph / 40km/h.
One can really hear/feel it work on front-drive models, as it makes the typical ABS type pulsating sound when activated during wheelspin. "
While it hasn't gotten good reviews from the street crowd at VW, Land Rover also uses these systems with success. Now I just have to find out if I can find a whiz who can get the code from the VW system and find a way to add it to the EBCM instructions in my truck... ahh, innovation
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
Philberto wrote:In line with my new project, is there anybody who can tell me if our ABS has the capability of individual braking (06+) and if the EBCM is what I should be looking to reprogram? I'd like to have a little bit of info before I go and ask the people I know. Also useful to me would be a source for a factory service manual and any other documentation I can get on the ABS, EBCM, and Traction control/stabilitrac systems.
I'm planning on trying to model an "offroad traction control" system after VW's Electronic Differential Lock system that engages brakes on any wheel doing 100rpm more than its neighbor. We'll see if I break any parts doing it, but hopefully everything will work out.
Taken from VW site:
"Electronic differential lock, or EDS (german acronym for same), is not a differential lock as per usual. It uses the ABS sensors at driven wheels (i.e. left/right front on FWD, left/right front and left/right rear on quattro), to determine if one of the two wheels is spinning faster than the other. At some speed differential (approximately 25 mph / 40 km/h), the highly sophisticated fifth-generation ABS/EBV actually pulsates the brake momentarily at the spinning wheel, effectively transferring the torque through the open differential to the wheel with more traction. This system is effective, but due to the stress that it would create on the braking system, it is only used up to speeds of about 25 mph / 40km/h.
One can really hear/feel it work on front-drive models, as it makes the typical ABS type pulsating sound when activated during wheelspin. "
While it hasn't gotten good reviews from the street crowd at VW, Land Rover also uses these systems with success. Now I just have to find out if I can find a whiz who can get the code from the VW system and find a way to add it to the EBCM instructions in my truck... ahh, innovation
From the roadie: Same idea as traction control, but you just have to hack into the ABS lock/purge valves. That would work for the front, if you have one spinning tire. In the rear on 2002-2005 before traction control, there is only one ABS channel for both rear wheels, so that won't work.
Yep, it'll work on the 06+ for front and rear if I can hack into the EBCM programming. While I'm there, I may also be able to add HAC and DAC, some fun bits from the Toyota LC's and Lexus LX's... HAC is Hill-start assist control, and simply holds the brakes on while you move your foot to the gas, and automatically releases when you apply power. DAC, Downhill assist control, individually applies brakes on each wheel to supplement 4lo engine braking and keep the vehicle moving in a straight line. All depends on if I can get into the EBCM. I'm going to find out after lunch when one of the techs gets back.
I'm hoping for the roadie to chime in on this, I know it's not high on the priority list, but if it ends up costing me nothing, then there's no harm in getting it, and if it ends up costing me a little, then I'll just sell the update to others here for a minimal amount and make back whatever I end up spending. It's looking like all that will be necessary is to generate a file that can be used to update the EBCM using a tech2 scantool. This should be able to be done at any GM dealership willing to load a custom file, and if that won't work, then I may end up handling the reprogramming myself, or I may talk to Kelly and Alvin at PCM4Less. Of course, I'm getting ahead of myself, but I'm really optimistic about this.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
Toyota Downhill Assist Control (Dac) and Hill Assist Control (HAC) In vehicles equipped with both HAC and DAC systems, an active wheel speed sensor is located in each wheel. The sensor uses a rotating magnetic encoder located in the wheel hub to detect a magnetic field. Once detected, it delivers digital signals based on the change of magnetic poles. The detection of the magnetic fields allows the use of magneto-resistive (MR) effects. The active wheel speed sensor is then able to measure the vehicle's extra low speed and rotating wheel direction.
Extra low speed detection is possible because the output signal of the active wheel sensor is proportional to the amplitude of a magnetic field. Because the magnetic field encoder does not depend upon the basic wheel rotation speed, the active wheel sensor can deliver a precise signal, even if the wheel speed is extra low.
The active wheel sensors detect rotation direction through the use of two MR elements. If the magnetic encoder detects a change in rotation, the phase between the two MR elements are shifted upside-down. This allows the active wheel sensors to digitally process the signals and provide wheel direction information. The sensor output is provided in three levels of current via a two-wired interface. In the case of a forward movement, the output is a two-level pulse signal. A three-level output pulse signal is provided in the event of backward movement.
The basic function of the HAC system is to help increase control on steep upgrades and stopping and starting on slippery surfaces. The HAC system is designed to help prevent the vehicle from rolling backward or slipping sideways during transition from a stopped position to climbing an upgrade. The system is automatically activated when the transmission is in any forward gear. The HAC system controls the brakes to help stop the individual wheel or wheels, which helps prevent the vehicle from rolling backward or slipping sideways.
The HAC system determines the driver's intended vehicle direction from the present gearshift position of the transmission, the moving direction of the vehicle wheels, and the wheel speed of the four wheels through the use of active wheel sensors. When backward rolling or slippage occurs, the HAC system is automatically activated. Upon activation the HAC system gently applies the brakes. The HAC system measures the necessary brake pressure of each wheel to help prevent individual wheels from locking and causing vehicle slippage.
The DAC system assists engine braking to improve directional control during descent on steep or slippery surfaces. When in 4WD low range and with DAC activated, if any one wheel accelerates beyond or below a two-to-four MPH low-speed setting, the DAC system will control the brakes to help ensure the vehicle continues in a straight position when going down a hill. The DAC system is automatically de-activated if the driver depresses the brake pedal, accelerator pedal, or the DAC button.
The active wheel speed sensors enable the operation of the DAC system by determining current road conditions. The system designed to determine current driver operation through an accelerator pedal angle sensor, master cylinder pressure sensor, and the setting of the L4 position switch. DAC next determines its target vehicle speed of two-to-four MPH based on road surface and vehicle driving conditions. When the vehicle accelerates during descent, allowing the vehicle speed to exceed the predetermined speed, DAC is activated. The DAC system will calculate the required brake hydraulic pressure for each wheel, allowing each individual wheel to meet the target vehicle speed.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
Well don't go congratulating me and opening the champagne just yet... at this stage, this is all purely conjecture, based on some sound research. The real test will be when I hook up the Tech2 and see what options I have vis a vis programming the BCM or EBCM. This also will only work with 06-07 TB's initially, as the 08+ TBs are CAN, and the earlier ones only have one channel in the rear. I may be able to work out the fronts only for them though... we shall see.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
I have EFILive Scan and Tune tool and download emailed tunes from Alvin without swappingo ut the PCMs. But EFILive just doesn't have bidirectional control over as many things as the tech tool does, though. Hmmm, if I was still working, I might have bought a used tech tool and have it onthe dash.
I've read about some other laptop-based programs that emulate a tech tool a bit better, though. And maybe they can talk to the individual valves.
Update: I've been talking to some of our GM techs, and I have strong support from them... I have free access to their TECH2 scanners, I'm going to probably be getting some BCMs from theft recovery vehicles, and I'm gonna be picking the BCM guy's brains over the next few days/weeks. The trick to making any major unofficial mods to the BCM is a VCI code. This is a code assigned by GM corporate to allow you to make a major change without having to have an official update downloaded. This is typically used to cover up screwups made in individual vehicle programming without having to initiate a recall (see FIGHT CLUB for more info on this). Anyways, if I can find out a way to emulate or generate VCI codes, then I should be able to reprogram any major computer component on any current GM vehicle. Once I get to the actual programming and find a way to upload it, I'll figure out how it's written, and from then on, it's simple to inject extra code into it to give it the additional function. I've got no interest in making this proprietary, so I'm putting all this info out there for you guys... consider it an "open source" project.
Alternatively, I may figure out manual actuation of the ABS valves and input signals from the wheel sensors, and I may just piggyback a separate module onto these signals to make everything simpler. I'll have to see after I look at a service manual.
My Build Thread | 2006 Trailblazer LS Desert Camping Edition **SOLD** 2013 Nissan Xterra S "ReXterra"
It may make sense to work the abs solenoids in reverse from your original idea.
Use the solenoid to block fluid flow to the wheels with grip. Allow free wheels to still receive modulated braking.
Have two dash switches. One would be to stop flow to front left, and rear right... the other would be opposite - stop flow to front right and rear left.
You get stuck with opposing wheels spinning. Engage appropriate switch, now apply brakes, then slowly apply throttle... once you regain traction on the braked wheels, release brakes, and deactivate the switch.
Just be careful not to activate both switches, or you lose all braking!!
Assuming the solenoids run off of 12V... could be easy as long as you know the pinout.
Gordinho80 wrote:
But if you'd like an explanation, I'd be happy to give you one.
you rock.gif
