Technical Panda 4x4 system test

[The Panda Nut]

ve

The system knows the size of the Fiat space saver... so the system knows it's being used and adjusts accordingly. Same with the 4x4 system, although (somewhere in the handbook) it says 'with reduced effectiveness' or words to that effect.
View attachment 458533

Saying a space saver provides less grip is so bad they really should be held to account. Its a great deal worse than less grip! Should say.... Space savers : Better than walking but to be treated with EXTREME caution as provide very little grip at all.

 

[Bonefish Blues]

ve

Saying a space saver provides less grip is so bad they really should be held to account. Its a great deal worse than less grip! Should say.... Space savers : Better than walking but to be treated with EXTREME caution as provide very little grip at all.

Not to mention that they are never pumped up, so when they're needed are often found to be at something like 20psi, rather than the 1784psi* needed.

*This is an estimate. It's probably a lot more

 

[The Panda Nut]

Not to mention that they are never pumped up, so when they're needed are often found to be at something like 20psi, rather than the 1784psi* needed.

*This is an estimate. It's probably a lot more

1784! Put your back into it man and buy a BIGGER footpump!
I must be a rarity but I do check all the spares regularly.
The space saver on our 2014 car requires just 42psi unlike the others which need the full 1784! It makes you wonder why that one is different. Maybe because it resembles (very strongly) a wheel barrow tyre?

I have added space saver tyre to both my daughters cars. One is a 165/65x14 Contineltal in place of the 175/65 it wears (I had a new one on the shelf) Then other is 175/65 x14 Falken in place of the 185 it wears. both the spares are painted bright yellow to ensure they dont run on the wrong size except in emergency. I am qiute sure these are better than space savers. The only reason I havnt don the same with my 4x4 is the dire warnings of gloom in teh handbook. I think I will try the other options from my daughters Pandas and see if teh 4x4 or warning lights misbehave. I can take it onto grass and try the ABS and traction control systems. One day I will report back.

 

[Eltezz]

For those of you, like me, who may be interested, I have found a breakdown of the rear differential internal parts. As I suspected, there is an internal clutch pack but for the life of me I cannot figure out how it is actuated. I don't think it is hydraulic as there is no evidence of any kind of pump mechanism. Might be direct (mechanical) or maybe air operated by that solenoid. Worth a look:

Rear Diff Panda 312/319

 

[Bonefish Blues]

What we really need is someone who's on good terms with the Fiat Workshop to ask the naive question.

Calling @Herts Hillhopper

 

[JayAre]

For those of you, like me, who may be interested, I have found a breakdown of the rear differential internal parts. As I suspected, there is an internal clutch pack but for the life of me I cannot figure out how it is actuated. I don't think it is hydraulic as there is no evidence of any kind of pump mechanism. Might be direct (mechanical) or maybe air operated by that solenoid. Worth a look:

Rear Diff Panda 312/319

According to ChatGPT it’s electromagnetic:

“The Fiat Panda 4x4 models from 2012 onwards (312/319) utilize an electromagnetic rear differential unit, not an electro-hydraulic one. This unit is a development of the system introduced in earlier generations of the Panda 4x4, but with improvements in efficiency, responsiveness, and control.

Evolution of the Panda 4x4 System​

1. Original "Dog-Leg" Differential Lock (Mk1 Panda 4x4 - 1983):​

• The first Panda 4x4, launched in 1983, used a simpler, purely mechanical four-wheel drive system.
• It featured a manually selectable four-wheel drive mode that engaged both axles using a secondary gear lever.
• A "dog-leg" differential lock (mechanical) was employed to split power between the front and rear axles. It was engaged manually and offered basic off-road capability.

2. Introduction of Viscous Coupling (Mk2 Panda 4x4 - 2003):​

• The second generation (2003–2012) replaced the manual system with a viscous coupling that automatically distributed torque between the front and rear axles.
• The viscous coupling system worked by detecting differences in rotational speed between the axles (slip) and then engaging the rear axle.
• This system was simpler and provided "on-demand" AWD, improving usability for everyday driving while maintaining off-road functionality.

3. Electromagnetic Rear Differential Unit (Mk3 Panda 4x4 - 2012):​

• The 312/319 series, introduced in 2012, evolved further by adopting an electronically controlled coupling, also referred to as an electromagnetic rear differential unit.
• This system is part of Fiat's AWD system (termed "Torque on Demand") and uses sensors to monitor road conditions, wheel speed, and traction needs.
• The rear differential is engaged or disengaged using an electromagnetic actuator that controls the clutch pack, allowing power to be sent to the rear wheels when slip is detected.
• This system provides faster response times, greater efficiency, and improved integration with stability control (ESP) and hill descent systems compared to the viscous coupling.

Key Advantages of the Electromagnetic System:​

• Speed and Efficiency: It reacts more quickly than viscous coupling systems, making it more suitable for modern driving dynamics.
• Control: Integration with other electronic systems allows for adaptive torque distribution, which is useful for both off-road conditions and slippery urban environments.
• Weight and Fuel Economy: The system is lighter and more efficient than older mechanical setups.

The move from manual engagement to viscous coupling and then to electromagnetic control reflects Fiat's focus on improving the usability and performance of the Panda 4x4 system, catering to a broader audience while retaining the model's off-road legacy.”

See this 2016 thread:

Fiat panda 4x4 2008 | FIAT Panda (Mk3)

Good day to all. There is a question, I want to buy a Fiat Panda 4x4 2008 release, but the dashboard is not found ELD button. How full the drive is running on this machine? Thank you

www.fiatforum.com

 

[Eltezz]

It was always going to be electromagnetic as the primary actuator is a solenoid. I am interested in how the clutch pack is operated internally. Studying the internal parts initially suggests the solenoid operates directly on the clutch (mechanical) but there seem to be various valves associated with it that make me wonder if some other method is being used, hence mentioning pneumatic.

 

[JayAre]

It was always going to be electromagnetic as the primary actuator is a solenoid. I am interested in how the clutch pack is operated internally. Studying the internal parts initially suggests the solenoid operates directly on the clutch (mechanical) but there seem to be various valves associated with it that make me wonder if some other method is being used, hence mentioning pneumatic.

Confusion seems to have arisen because the 169—> 312/9 4x4 was not a single switch from viscous coupling to the much more complex electronically controlled system but was instead an evolution via the final iterations of 169 4x4 production when “ELD” was first introduced, and those final years 169 4x4 models apparently DID use an electro hydraulic system:

Home Page

aftersales.fiat.com

 

[Panda IIs]

For those of you, like me, who may be interested, I have found a breakdown of the rear differential internal parts. As I suspected, there is an internal clutch pack but for the life of me I cannot figure out how it is actuated. I don't think it is hydraulic as there is no evidence of any kind of pump mechanism. Might be direct (mechanical) or maybe air operated by that solenoid. Worth a look:

Rear Diff Panda 312/319

Fascinating. Some tantalising detail but still no obvious functional schematic. As you say the part described as "sprocket assembly" appears to be some kind of multiplate clutch with splined input (male) from the prop shaft and splined socket (female) for the diff pinion shaft. Inspection of the solenoid rendering doesn't really give many clues although maybe it just presses on the outer casing of the clutch pack? The slowing of the outer casing transfers drive to the diff pinion? I'm wracking my brain since I think I have come across something like this before but can't think where.

If this is the case then there would be some friction material or the like on the solenoid plunger??? All pure speculation now which I shouldn't be engaging in Has anyone pulled the solenoid out?

 

[Bonefish Blues]

So it's done by pixies, yes?

 

[Eltezz]

Pixies almost certainly had a hand in this…

 

[Panda IIs]

Pixies almost certainly had a hand in this…

With their smoke and mirrors too.

 

[JayAre]

Fascinating. Some tantalising detail but still no obvious functional schematic. As you say the part described as "sprocket assembly" appears to be some kind of multiplate clutch with splined input (male) from the prop shaft and splined socket (female) for the diff pinion shaft. Inspection of the solenoid rendering doesn't really give many clues although maybe it just presses on the outer casing of the clutch pack? The slowing of the outer casing transfers drive to the diff pinion? I'm wracking my brain since I think I have come across something like this before but can't think where.

If this is the case then there would be some friction material or the like on the solenoid plunger??? All pure speculation now which I shouldn't be engaging in Has anyone pulled the solenoid out?

“Internal Actuation of the Clutch Pack
In the Panda 4x4’s electromagnetic differential system, the solenoid (electromagnetic actuator) plays a central role in controlling the clutch pack:

1. Electromagnetic Actuator:
   • The solenoid generates a magnetic field when activated by the vehicle’s control module.
   • This magnetic field moves an actuator pin or arm, which applies pressure to a mechanical linkage connected to the clutch pack.
2. Clutch Engagement:
   • The actuator pin directly compresses a stack of friction plates and steel plates in the clutch pack.
   • The degree of compression determines how much torque is transmitted to the rear axle. Partial compression allows some slip, while full engagement locks the clutch pack.
3. Hydraulic Assistance via Valves:
   • While the electromagnetic actuator provides the primary force, the system uses hydraulic pressure to modulate the clutch engagement. The hydraulic fluid is controlled by valves that regulate pressure in response to inputs from sensors (wheel speed, throttle position, and traction conditions).
   • These valves ensure smooth operation by providing progressive engagement rather than an abrupt lock-up.
4. Sensors and Electronic Control:
   • The control unit monitors traction conditions in real-time, using inputs from wheel speed sensors and the ESP system. Based on these inputs, it determines how much torque needs to be transferred to the rear wheels.
   • The solenoid and valves are controlled dynamically to optimize torque distribution, engaging the clutch pack only when necessary.

The system involves a combination of mechanical and hydraulic mechanisms:

• The solenoid applies direct mechanical force to the clutch pack.
• Hydraulic components (likely modulated by solenoid-driven valves) assist in fine-tuning the actuation, ensuring smooth and precise torque transfer.

This hybrid approach combines the responsiveness of electromagnetic actuation with the smoothness of hydraulic modulation. The design minimizes wear on the clutch pack and enhances the system's durability and efficiency.”

 

[Panda IIs]

“Internal Actuation of the Clutch Pack
In the Panda 4x4’s electromagnetic differential system, the solenoid (electromagnetic actuator) plays a central role in controlling the clutch pack:

1. Electromagnetic Actuator:
   • The solenoid generates a magnetic field when activated by the vehicle’s control module.
   • This magnetic field moves an actuator pin or arm, which applies pressure to a mechanical linkage connected to the clutch pack.
2. Clutch Engagement:
   • The actuator pin directly compresses a stack of friction plates and steel plates in the clutch pack.
   • The degree of compression determines how much torque is transmitted to the rear axle. Partial compression allows some slip, while full engagement locks the clutch pack.
3. Hydraulic Assistance via Valves:
   • While the electromagnetic actuator provides the primary force, the system uses hydraulic pressure to modulate the clutch engagement. The hydraulic fluid is controlled by valves that regulate pressure in response to inputs from sensors (wheel speed, throttle position, and traction conditions).
   • These valves ensure smooth operation by providing progressive engagement rather than an abrupt lock-up.
4. Sensors and Electronic Control:
   • The control unit monitors traction conditions in real-time, using inputs from wheel speed sensors and the ESP system. Based on these inputs, it determines how much torque needs to be transferred to the rear wheels.
   • The solenoid and valves are controlled dynamically to optimize torque distribution, engaging the clutch pack only when necessary.

The system involves a combination of mechanical and hydraulic mechanisms:

• The solenoid applies direct mechanical force to the clutch pack.
• Hydraulic components (likely modulated by solenoid-driven valves) assist in fine-tuning the actuation, ensuring smooth and precise torque transfer.

This hybrid approach combines the responsiveness of electromagnetic actuation with the smoothness of hydraulic modulation. The design minimizes wear on the clutch pack and enhances the system's durability and efficiency.”

Aha, still some smoke and mirrors

These parts are described as valves from @Eltezz post above - looking like spring loaded relief valves - still requiring a sprinkle of pixie dust?

 

[Herts Hillhopper]

Having found the answer direct from Fiat, I’ve started a new thread called, imaginatively, ‘How the 4x4 system works’.

Chat GPT was close… but perhaps less clear.

 

[Bonefish Blues]

What we really need is someone who's on good terms with the Fiat Workshop to ask the naive question.

Calling @Herts Hillhopper

Who then resorted to reading the bloody manual FGS! I mean, what good's that ever done?

 

[The Panda Nut]

For those of you, like me, who may be interested, I have found a breakdown of the rear differential internal parts. As I suspected, there is an internal clutch pack but for the life of me I cannot figure out how it is actuated. I don't think it is hydraulic as there is no evidence of any kind of pump mechanism. Might be direct (mechanical) or maybe air operated by that solenoid. Worth a look:

Rear Diff Panda 312/319

That is pure gold dust too. Many thanks for posting. These things need to go in downloads too!

 

[The Panda Nut]

What sort of cunning b-stard thought this all up. Its really IN credible. Panda 4x4 is surely the best car ever. This and the TA make it the most interesting by a country mile.

 

[JayAre]

Panda 4x4 system “slip tests” - auto v ELD/Off Road

Cross v Suzuki Ignis All Grip


Cross v Dacia Duster

 

[Herts Hillhopper]

Yup, when there’s zero grip, especially for both front wheels, going anywhere is tricky. True for all 4x4s. But on many surfaces, the likelihood is that there will be different grip levels at different wheels. Otherwise, that’s when a winch is needed
The same is true of ABS: if all four wheels lock at the same time — such as a sheet of black ice — the car thinks it’s standing still (because none of the wheels are rotating) so the ABS does nothing.
I don’t know if there’s any common stuff between tbe Ignis and the Panda? At one point Fiat and Suzuki sold an identical car except for the badge… (SX4 and Sceicenti?)