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Technical Fiat panda 4x4 2008
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Technical Fiat panda 4x4 2008
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this car four-wheel drive is automatically activated?
ELD button allows you to automatically connect all wheel drive?
johnbushell
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ELD or Electronic Locking Diff is only on the latest 4x4's (319) and is not fitted to the older models (169).
It does not actually lock the diffs but basically uses the stability control/abs to monitor each wheel and direct torque to the wheels by applying the brakes to slipping wheels.
It also over rides the torque on demand and locks it into 4x4, so will split the power between both axles rather than waiting for the fronts to slip before the coupling starts shunting power to the rear axle.
With a normal open diff, if one wheel on an axle looses traction, that would cause the other wheel to diff slip, so will not transmit any power.
This means there's no traction on that axle as one wheel is spinning due to no traction, the other with no torque due to open diff slip.
ELD will detect the spinning wheel and apply the brake to that wheel, thus sending torque to the other wheel on that axle that would normally diff slip due to the open diff (and hopefully that has grip).
The system can help, but it works "after the fact", you have already lost traction somewhere before it kicks in!
I've a later 4x4 (319) with ELD and I've never really needed it (yet) as it's so good in normal drive, stunningly good!
I regularly get it off road in boggy fields, dirt tracks and recently a little snow and nothing yet has even caused it to struggle, let alone felt like it might be about to struggle, even when pulling my trailer.
One thing I would suggest is fitting decent mud/snow rated tyres (like those fitted to the newer 319's)
These will be enough in most situations (including the road) as the car is so light it barely sinks or digs in like heavier cars.
I regularly see XC90's and the likes bog down while I just scoot away, skimming across the top of the mud.
It does not actually lock the diffs but basically uses the stability control/abs to monitor each wheel and direct torque to the wheels by applying the brakes to slipping wheels.
It also over rides the torque on demand and locks it into 4x4, so will split the power between both axles rather than waiting for the fronts to slip before the coupling starts shunting power to the rear axle.
With a normal open diff, if one wheel on an axle looses traction, that would cause the other wheel to diff slip, so will not transmit any power.
This means there's no traction on that axle as one wheel is spinning due to no traction, the other with no torque due to open diff slip.
ELD will detect the spinning wheel and apply the brake to that wheel, thus sending torque to the other wheel on that axle that would normally diff slip due to the open diff (and hopefully that has grip).
The system can help, but it works "after the fact", you have already lost traction somewhere before it kicks in!
I've a later 4x4 (319) with ELD and I've never really needed it (yet) as it's so good in normal drive, stunningly good!
I regularly get it off road in boggy fields, dirt tracks and recently a little snow and nothing yet has even caused it to struggle, let alone felt like it might be about to struggle, even when pulling my trailer.
One thing I would suggest is fitting decent mud/snow rated tyres (like those fitted to the newer 319's)
These will be enough in most situations (including the road) as the car is so light it barely sinks or digs in like heavier cars.
I regularly see XC90's and the likes bog down while I just scoot away, skimming across the top of the mud.
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Sweetsixteen
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When I bought my Panda Multi, I first went for a 4 wheel drive model, but as I already had a Jeep I bought the bog standard 2 wheel drive. I put M+S tyres on it, and so far - muddy farm tracks and boggy fields - it has always amazed me with its traction.
When the time comes to change it I will get a 4 wheel drive Panda, just for kicks, but I really haven't needed one yet.
Amazing little cars!
When the time comes to change it I will get a 4 wheel drive Panda, just for kicks, but I really haven't needed one yet.
Amazing little cars!
Actually, it was fitted to the previous model, but only the Cross spec in the UK. (It was also available as an option on some EU counties on the 4x4 model, but only from 2010 onward.
However, even without ELD, the 2008 4x4 has fully auto engagement of 4x4 via the viscous coupling, as others have said
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I thought the original Cross had a version of ELD (not sure if it's the same as later models though).
But I presumed the OP was asking about the Climbing as most refer to that as the 4x4 and the Cross as the Cross.
Yes, all 4x4/Climbing/Cross models drive all four wheel, but the coupling under normal conditions on all these models only transmits a small amount of torque to the rear, that is until the fronts start to slip, then it will automatically shunt up to 50% to the rear when needed.
The 169 Climbing used a viscous coupling to do this and the later model an electromagnetic coupling.
This electromagnetic system allows for the ELD to lock the coupling where the viscous doesn't (not easily).
So when it's engaged it will split torque uniformly between both axles from the off, without the need for the front axle to slip.
Due to this, it's function is speed limited to 31 mph, there's a risk of damage due to wind up (and damage due to it not going around corners!)
Does the original Cross uses this electromagnetic system and have the full ELD locking system or did it use viscous still and only get the stability control/abs wheel braking part?
I thought there were various cost/weight/reliability reasons that the viscous system didn't get a full front to back lock.
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For the OPs question, correct, a 2008 Climbing was not available with ELD and it used a viscous coupling to distribute the drive as needed. So OP shoudl not see ELD button.
But, the very last of the 169 4x4s including the Cross saw Fiat move from the viscous coupling to one with electronic engagement. There was even a recall on the 169 Cross model to replace the solenoid that operated this. The 2010 Cross had ELD that worked as on the new 319 Panda (although the actual rear diff design is changed for the post 2012 car)
But, the very last of the 169 4x4s including the Cross saw Fiat move from the viscous coupling to one with electronic engagement. There was even a recall on the 169 Cross model to replace the solenoid that operated this. The 2010 Cross had ELD that worked as on the new 319 Panda (although the actual rear diff design is changed for the post 2012 car)
jaywalk
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I've also been wondering about which Panda 4x4's have which systems installed, so this was a good thread! To summarize, as I understand it:
* Panda mk III 4x4 Climbing: Viscous coupling, open differentials. Exeptions post 2010.
* Panda mk III 4x4 Cross: Electro-magentic coupling, open differentials (with ELD).
* Panda mk IV 4x4 (Cross and non-Cross): Electro-magnetic coupling, open differentials (with ELD).
I own a mk III 4x4 Climbing and it is indeed all passive and works at all speeds and cannot be disabled (something the MOT moans about since that means their normal break test doesn't work).
What I wonder is how the electronic systems on those three later models above work. I've read that the new mk IV Cross has a little control that allows you to lock the magnetic coupling making it constant all wheel drive, I guess in conjunction with the ELD dynamically breaking to move tourque over each differential when needed/slipping?
How does the other two (mk IV 4x4 non-cross and mk III 4x4 Cross) work? Does this ELD button activate all systems (electro-magnetic coupling, ELD on rear and front diff) and are they all disabled otherwise?
How does the electro-magentic coupling distribute power between front/rear axle? I expect it is as with the viscous copling, a maximum of 50:50 ratio (never more than 50% to the rear)? What governs how much tourque is transmitted to the rear, is it the ABS detecting slipping as with the ELD differentials?
* Panda mk III 4x4 Climbing: Viscous coupling, open differentials. Exeptions post 2010.
* Panda mk III 4x4 Cross: Electro-magentic coupling, open differentials (with ELD).
* Panda mk IV 4x4 (Cross and non-Cross): Electro-magnetic coupling, open differentials (with ELD).
I own a mk III 4x4 Climbing and it is indeed all passive and works at all speeds and cannot be disabled (something the MOT moans about since that means their normal break test doesn't work).
What I wonder is how the electronic systems on those three later models above work. I've read that the new mk IV Cross has a little control that allows you to lock the magnetic coupling making it constant all wheel drive, I guess in conjunction with the ELD dynamically breaking to move tourque over each differential when needed/slipping?
How does the other two (mk IV 4x4 non-cross and mk III 4x4 Cross) work? Does this ELD button activate all systems (electro-magnetic coupling, ELD on rear and front diff) and are they all disabled otherwise?
How does the electro-magentic coupling distribute power between front/rear axle? I expect it is as with the viscous copling, a maximum of 50:50 ratio (never more than 50% to the rear)? What governs how much tourque is transmitted to the rear, is it the ABS detecting slipping as with the ELD differentials?
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Both basic front to rear torque systems perform similarly, though one is mechanical and the other electronically control.
The viscous coupling on the Climbing is basically two shafts joined together by plates in a tube filled with thick fluid.
Every other plate lock into one shaft, the others in between lock into the other shaft. (very similar to a motorbikes wet clutch).
With no pressure on the plates, they slip past one another and no torque transmits from one shaft to the other.
When it all starts slipping the thick fluid drags on the plates, thus sending torque through it, the more slip the more drag on the plates, the more torque.
It's totally automatic and self regulating.
The later models with the electronic system uses a power transfer unit on the back of the gearbox with an electromagnetic actuator to engage and disengage a dog clutch (inter locking cogs) to transmit power to the rear axle.
The system is controlled by the powertrain ECU and uses sensors to detect when and how much power is needed to the rear.
Now where they differ is with this electronic system, it's easier to over ride and lock the transmission 50/50 than it is to lock a viscous coupling, it's just a matter of signalling the electromagnetic actuator.
(this locking is part, but not all of what the ELD system)
Where as to pre lock the viscous, there needs to be some way of altering the state of the fluid in the system (pump) or some other way of locking the two shafts together.
I believe due to weight/cost/reliability Fiat did not include a front to back lock on this viscous system.
So both can alter power centrally between front and rear axles, though only the later electronic system can pre lock the front to back transfer of torque.
Due to the other systems these later models have, like the stability control (ESC) along with the ABS, they can also "lock" the diffs on each axle (side to side), though it's not a true lock, just the effects are similar.
By using the ESC it can detect a slipping wheel and using the ESC & ABS systems it can grab that brake (as it would on the road, just now it's works with smaller amounts of wheel speed differences), thus sending that axles torque to the other wheel, which normally due to the open diff would not have received any torque (it would have all spun away on the slipping wheel).
This is the other part of the ELD system, by pressing the button you pre lock the front to back diff and alter the ESC system it already has to grab brakes on slipping wheels.
Really it just using the systems it already has, mainly the ESC, but by pressing the button it's using a different set of perimeters.
Now the later Cross model takes this electronic system a bit further.
Instead of the ELD being on or off, the system has different settings to allow for different conditions.
So for mud it might lock front to back 50/50 and jack the "mock" front and rear diff locks reaction times right up as it knows it's going to be searching for grip, for gravel it might back the system off slightly as it's a bit loose, but grip is there somewhere. Hill decent might jack up the ABS response and again alter the front to back power split to a more favourable setting.
As I said before, without all this electronic "locking", it's still very capable on the slippy stuff in normal mode.
I just sit there and blaze away through, it's worked so far!
The viscous coupling on the Climbing is basically two shafts joined together by plates in a tube filled with thick fluid.
Every other plate lock into one shaft, the others in between lock into the other shaft. (very similar to a motorbikes wet clutch).
With no pressure on the plates, they slip past one another and no torque transmits from one shaft to the other.
When it all starts slipping the thick fluid drags on the plates, thus sending torque through it, the more slip the more drag on the plates, the more torque.
It's totally automatic and self regulating.
The later models with the electronic system uses a power transfer unit on the back of the gearbox with an electromagnetic actuator to engage and disengage a dog clutch (inter locking cogs) to transmit power to the rear axle.
The system is controlled by the powertrain ECU and uses sensors to detect when and how much power is needed to the rear.
Now where they differ is with this electronic system, it's easier to over ride and lock the transmission 50/50 than it is to lock a viscous coupling, it's just a matter of signalling the electromagnetic actuator.
(this locking is part, but not all of what the ELD system)
Where as to pre lock the viscous, there needs to be some way of altering the state of the fluid in the system (pump) or some other way of locking the two shafts together.
I believe due to weight/cost/reliability Fiat did not include a front to back lock on this viscous system.
So both can alter power centrally between front and rear axles, though only the later electronic system can pre lock the front to back transfer of torque.
Due to the other systems these later models have, like the stability control (ESC) along with the ABS, they can also "lock" the diffs on each axle (side to side), though it's not a true lock, just the effects are similar.
By using the ESC it can detect a slipping wheel and using the ESC & ABS systems it can grab that brake (as it would on the road, just now it's works with smaller amounts of wheel speed differences), thus sending that axles torque to the other wheel, which normally due to the open diff would not have received any torque (it would have all spun away on the slipping wheel).
This is the other part of the ELD system, by pressing the button you pre lock the front to back diff and alter the ESC system it already has to grab brakes on slipping wheels.
Really it just using the systems it already has, mainly the ESC, but by pressing the button it's using a different set of perimeters.
Now the later Cross model takes this electronic system a bit further.
Instead of the ELD being on or off, the system has different settings to allow for different conditions.
So for mud it might lock front to back 50/50 and jack the "mock" front and rear diff locks reaction times right up as it knows it's going to be searching for grip, for gravel it might back the system off slightly as it's a bit loose, but grip is there somewhere. Hill decent might jack up the ABS response and again alter the front to back power split to a more favourable setting.
As I said before, without all this electronic "locking", it's still very capable on the slippy stuff in normal mode.
I just sit there and blaze away through, it's worked so far!
jaywalk
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Very true! I'm not a 4x4-guy, but I've never driven a car that stays on the road like my Panda. And there's been plenty of snow and ice to challenge it during the winters.
I'm asking / trying to figure it out since I am an engineer at heart and just can't stand not understanding any interesting contraption I encounter.
Thanks for the explainations, think that covers it and is as I expected! One more point, as I understand the reason for my Panda 4x4 Climbing not being available with ESC/ABS is that the viscous coupling needs that wheel spin to activate and engage the rear axle drive. Guess that's one of the big benefits of the electrically engaged 4x4 systems.
Interesting to hear that there exists controllable viscous couplings as you describe, not something I've ever encountered!
Correct - the 4x4 did have ABS, but could not have stability control as the front wheels had to spin (not much though) to make the viscous coupling connect.
The electronic coupling on later models is at the rear, in place of the viscous unit on the 'nose' of the rear diff casing- and can vary the degree of connection between 98% front and 50/50. If you press the 'ELD' button on the newer 4x4, or turn the dial in the new Cross to 'offroad' this does two things - it allows ELD to operate (if it needs to - a dash light shows it has operated), and it forces 50/50 front/rear drive.
Not quite. The new Cross dial has three settings: auto, offroad and hill descent.
- 'Auto' is the same as the new 4x4 with nothing pressed (so its a setting that changes nothing! - the non-Cross 4x4 is in this mode 'by default').
- 'Offroad' has same effect as pressing 'ELD' on the new 4x4: it fixes the drive train at 50/50 front/rear dive, and it 'allows' ELD to work if it needs to (this is a 'mock' diff lock, not affecting the diff at all, but which applies the brake to a wheel that is spinning free). It also turns off ESC and I believe alters the throttle behaviour too.
- Hill descent allows the ABS to brake each wheel separately, without the driver touching the brake pedal, to hold the car back to a crawl going down hill without causing any wheels to lock.
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