It's identical to an ABS monitoring system...
Did they have ABS?
Did they have ABS?
Diesel Do
Well-Known Member
Is it? The speed differences wouldn't be big enough! Abs relies on a significant speed difference to work, every component of the 4x4 system can be driven by the road or the gear box so if you have a failed vcu it won't show? You would need to measure the wind up using strain gauges or similar?!
The speed difference would be a a function of the pulse rate - easy to adjust.
Open Circuit would give you a near constant difference betwen input and output and, therefore an easily identifyible fault condition.
As for normal use - there would be a variable range which should be acceptable and therefore an identifyable fault condition if there was less than expected variation.
with all the electronics currently on board, it would be easy to have a differential feed from the ABS sensor circuit to act as a reference signal.
Not insurmountable problems.
Open Circuit would give you a near constant difference betwen input and output and, therefore an easily identifyible fault condition.
As for normal use - there would be a variable range which should be acceptable and therefore an identifyable fault condition if there was less than expected variation.
with all the electronics currently on board, it would be easy to have a differential feed from the ABS sensor circuit to act as a reference signal.
Not insurmountable problems.
but thats the point - they dont! - if they did, there wouldnt be a problem - or a need for diffs
.
Diesel Do
Well-Known Member
That's a normal speed difference of cornering etc which the vcu allows for! Soo you'd pick that up! False alarm! For seized you'd be looking for front and rear to have a speed difference which you'd measure at the wheels! because of the ird gearing! But that doesn't happen cos the road forces the wheels to do whatever speed they must. If the vcu was seized solid the rear would go a different speed to the front destroying the tyres. That doesn't happen. So you'd need to measure either side of the vcu which under normal driving in a straight line will be going at different speeds that's dictated by the gearing and the tyre grip. That doesn't change even when it's semi seized! You just get wind up not speed differences unless you're on a slippery surface in which case the vcu may make the rear go at a different speed to the front!
DD3
New Member
Exactly - and thats why they are de facto ****e! We will all either go back to LRs with diff locks or forward to Haldex depending on preferences and budget. Just my opinion!
Tiz a question of tolerances - all identifiable and capable of being programmed into a system. Dont be a Luddite. In this day n age, tiz a relatively easy job to compare LF/LR,RF/RR and VCUF & VCUR rotational speeds and come up with values for acceptable and not acceptable figures. For example if a wheel spins, you would expect the Rotational speed on that wheel to increase significantly, with a sharp spike in the VCUF/VCUR difference, closely followed by a VCUF/VCUR diffential of ) as the VCU locks up. Simple example, but it shows would could be anticipated to happen. If there is a large VCU change then the VCU is not locking up (ie Open Circuit), or if the VCU speed doesnt increase at all, then the VCU is siezed. Between those two variations are a range of acceptable/ Unacceptable figures.
I am not saying it is easy, just that it isnt outside the realms of an electronic designer with a small PIC chip. Even if it was only used in a known state (Wheel spin), it could be a useful test circuit.
If you dont get any variations, explain how the VCU increases in temperature? This is caused totally by heat generated by internal friction between the contra-rotating plates. This suggests, to me at least, that there must be some difference between input and output shaft speeds, otherwise the VCU would stay at ambient temperature.
Unfortunately, despite the best efforts of Hippo, myself & others, we still seem to be "****ing into the wind" as far as knowledge on the VCU and its usual operating parameters are concerned.
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DD3
New Member
Its a crude device that does a job for the most part. I'm no fan of gizmos and such on cars but in this area, the technology has moved on for the better. I suspect that you chaps know more about VCU's than LR ever did
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Like most things on LRs - when it works, it works Ok. Its major drawback is that if (when) it fails, it can be catastrophic. All it would have needed was a shear pin (or similar) built in to it, so that instead of winding up the complete transmission, the weak point was easily identified and gave warning first. Unfortunately for us - it is "our " problem as it happens out of warranty. LR arent concerned.
Bromsgrove Defender
Well-Known Member
Did LR come up with their own version of the Haldex the result being the VCU and IRD in the FL1???.......
That would explain why they went down the Haldex route with the FL2
Nothing wrong with the concept just the execution.................
IMHO
Sending the right amount of drive to the right wheel in all circumstances is only really doable with computer controlled drive, which as I can see at the moment is only going to be achieved with an electric motor at each wheel
I dont even want to go there!!
That would explain why they went down the Haldex route with the FL2
Nothing wrong with the concept just the execution.................
IMHO
Sending the right amount of drive to the right wheel in all circumstances is only really doable with computer controlled drive, which as I can see at the moment is only going to be achieved with an electric motor at each wheel
I dont even want to go there!!
Did LR come up with their own version of the Haldex the result being the VCU and IRD in the FL1???.......
That would explain why they went down the Haldex route with the FL2
Nothing wrong with the concept just the execution.................
IMHO
Sending the right amount of drive to the right wheel in all circumstances is only really doable with computer controlled drive, which as I can see at the moment is only going to be achieved with an electric motor at each wheel
I dont even want to go there!!
The Nissan Juke 4x4 Auto - individual wheel speed control - supposed to be awesome (but in a bad way) - uses Torque Vectoring!!
:faint2:.Lateral torque vectoring capability. This not only splits torque between front and rear axles, but from side-to-side across the rear axle as well. The system counts wheel speed, steering angle, yaw rate and lateral G to distribute torque, and is effective in reducing understeer. In total, up to 50% of total available engine torque can be sent to either rear wheel. The rear axle incorporates electric couplings at either end plus a new final-drive.
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Bromsgrove Defender
Well-Known Member
The Nissan Juke 4x4 Auto - individual wheel speed control - supposed to be awesome (but in a bad way) - uses Torque Vectoring!!
Lateral torque vectoring capability. This not only splits torque between front and rear axles, but from side-to-side across the rear axle as well. The system counts wheel speed, steering angle, yaw rate and lateral G to distribute torque, and is effective in reducing understeer. In total, up to 50% of total available engine torque can be sent to either rear wheel. The rear axle incorporates electric couplings at either end plus a new final-drive.
Ok not electrically powered but electrically controlled
Still wouldn't want to go there
Bromsgrove Defender
Well-Known Member
I can see it now
The All Noo FL3
wiv
Lectrickal individual wheel speed control
Just don't get it wet cos the doors and the wheels fall orft
The All Noo FL3
wiv
Lectrickal individual wheel speed control
Just don't get it wet cos the doors and the wheels fall orft
Hippo
Lord Hippo
I guess the big problem we have is not it going wrong over time (because we can spot that if we test regular and know average test results) it's the peeps who don't test or don't know there could be a problem. They find out when something eggspensive snaps. So your right there isn't a fail safe option like going open circuit if too hot or too much torque. Hence no fail safe protection from the major cause of eggpensive things snapping.
I agree with the other stuff you said about electrical monitoring of wheels. ABS and TC was an option on FL1 when new. Became standard fit in 2001 model year (started late 2000). That uses electronics to monitor wheels turning. The monitoring process you mention above could easily be done by LR or an after market company who could supply a solution. They would then be able to call themselves true tranmissions eggspurts.
A bit like us then ?
