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Yes, this is the base difference between RWD and FWD.

Back in topic, as I understand Giulia has LSD with no more than 25% lock. It's done for better traction in a fast slippery curves, not for off-road.
Good winter tires are always helpful in a winter, with studs are even better. It does not matter what type of traction car has, tires are the key.

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For a Torsen the spec would be torque bias ratio. The lower the torque bias ratio the less torque transfer can occur. 2.5:1 is common. Generally speaking the lower the torque bias ratio the more the diff acts as if completely open. A lower TBR is better for road use.

The BRZ is reputed to have a high TBR and can be a handful in slippery conditions as the torque can get pushed back and forth across the axle quite rapidly making it tricky to drive straight. On dry road this makes provoking a drift easier which is why I think Subaru/Toyota chose the higher TBR than would be ideal.

Mechanical clutch type LSD vary the degree of slip permitted before lock up by selecting different angles for the torque reaction pin to slide in, usually different between drive and overrun also. Initial slip resistance is set by internal spring pressure (Belleville washers) Wear can be severe if very grippy tires are used.
 

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Regarding Hopkirk in the Mini in the Monte and in the snow.

One of the car journalists suggested that with Hopkirk being sideways so much, the driving lights should have been mounted on the doors.

:)
It is possible to perform low speed donuts in a 164 on snow using the handbrake turn technique, accurate throttle and appropriate steering lock.

I very much doubt there is enough handbrake torque available to handbrake turn a 164 accurately enough on bare road.....

As for driving fwd downhill in snow or on ice, just use the brakes which operate on all four wheels. Trouble with relying on engine braking with fwd is the limit of traction is reached in the transition between drive and overrun. As weight transfers forwards when you lift off the front tires increase grip. The rear tires lose grip. Anticipating the effect of engine braking is much more difficult than the effect of braking. The safest way to handle this transition is to depress the clutch as you initially brake. This maintains the front to rear grip ratio while the weight transfer is minimized. Otherwise, both ends of the car can loose grip at unexpected times making the descent basically a gambling exercise. The front can grab or skid during the weight transfer depending on how much grip is available, same at the rear for opposite reasons. Using just the brakes automatically biases the grip slightly forwards so that the car will understeer first. Of course abs is a boon for this method.

Using the throttle and the clutch while cornering the 164 in snow or on ice can reduce the risk of terminal understeer and get you round the corner. Swedish rally drivers perfected all this with left foot braking and the Scandinavian flick.
 

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For a Torsen the spec would be torque bias ratio. The lower the torque bias ratio the less torque transfer can occur. 2.5:1 is common. Generally speaking the lower the torque bias ratio the more the diff acts as if completely open. A lower TBR is better for road use.

The BRZ is reputed to have a high TBR and can be a handful in slippery conditions as the torque can get pushed back and forth across the axle quite rapidly making it tricky to drive straight. On dry road this makes provoking a drift easier which is why I think Subaru/Toyota chose the higher TBR than would be ideal.

Mechanical clutch type LSD vary the degree of slip permitted before lock up by selecting different angles for the torque reaction pin to slide in, usually different between drive and overrun also. Initial slip resistance is set by internal spring pressure. Wear can be severe if very grippy tires are used.
I am not sure what type of LSD is in Giulia. Just known it is rear differential unit RDU 230-LSD. Curious fact, the weight of LSD unit is 6 kg more than non locked unit :) (32 and 26 kg)


Torsen was used in FWD applications such as 147/GT 1.9 JTDm Q2.
Philippe Kreif was responsible for the development of those models.


In 159/Brera/Spider was used fake LSD, it was imitated by brakes.

Also LSD for FWD was used in racing 155/156, it helped to keep the car stable in curves under braking.
 

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"Using the throttle and the clutch while cornering the 164 in snow or on ice can reduce the risk of terminal understeer and get you round the corner. Swedish rally drivers perfected all this with left foot braking and the Scandinavian flick"

Yup, been there, done that. Used to be just a ton of fun.
 

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"Using the throttle and the clutch while cornering the 164 in snow or on ice can reduce the risk of terminal understeer and get you round the corner. Swedish rally drivers perfected all this with left foot braking and the Scandinavian flick"

Yup, been there, done that. Used to be just a ton of fun.
Can't be done using a ZF automatic.....

:cool:
 

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I am not sure what type of LSD is in Giulia. Just known it is rear differential unit RDU 230-LSD. Curious fact, the weight of LSD unit is 6 kg more than non locked unit :) (32 and 26 kg)
...

In 159/Brera/Spider was used fake LSD, it was imitated by brakes.

Also LSD for FWD was used in racing 155/156, it helped to keep the car stable in curves under braking.
According to ZF they supply their HAG diff for the Giulia base and Ti models. The optional diff is a ZF multiplate style which will use the pin in ramped slot to apply pressure to the friction plates.

https://www.zf.com/corporate/en_de/products/stars_by_zf/sbzf_cars/index.html#product=29292
 

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OK back to the topic at hand:

People with the Performance Package seem to indicate that there is a lot less traction or stability control interference than on the cars without the Q2 package.

I wonder if this means the diff is doing a better job putting power to the ground, thus limiting the need for interference? Or possibly that the electronics are tuned differently on this model? Or both?
 

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OK back to the topic at hand:

People with the Performance Package seem to indicate that there is a lot less traction or stability control interference than on the cars without the Q2 package.

I wonder if this means the diff is doing a better job putting power to the ground, thus limiting the need for interference? Or possibly that the electronics are tuned differently on this model? Or both?
Performance package has electronic shock absorbers + LSD + probably different tires = better traction and the electronics are tuned differently.

And obviously it is not stability control interference but traction control. Stability control works without any indication.
 

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A guy who lives in snowy Montreal posts that the traction control in snow is hopeless. Keeps brake-snubbing the spinning wheel until the car can't move.
In October, a friend toured part of Italy in a rented small, but good-performing hatchback. Had TC on the front wheel drive. Going up a steep gravel road the TC keep snubbing the slipping wheel until the car came to a stop. Even with his foot on the peddle.
Backed off and took a scary run at it--and made it.
He is an experienced slalom competitor and motorcyclist.
It is just a common sense to turn ESC off when stuck in a snow, sand or mud to allow the wheel spin. If the driver is not acknowledgement how to drive in a snow/sand/mud/ice he/she should take driving courses again
 

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Are the tires the same? ... stickier tires will definitely quieten down a pesky traction/stability control as well as intrusive ABS a fair bit.

OK back to the topic at hand:

People with the Performance Package seem to indicate that there is a lot less traction or stability control interference than on the cars without the Q2 package.

I wonder if this means the diff is doing a better job putting power to the ground, thus limiting the need for interference? Or possibly that the electronics are tuned differently on this model? Or both?
 

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I pretty sure stability and traction control software doesn't need modifying for tire grip, or for any chassis changes. The traction control is purely wheelspeed control. Wheelspin inputs infer loss of grip and the traction control reduces torque to that contact patch by applying brake pressure (and as the driver continues to ignore the effects reduces engine power as well by dumping boost, retarding ignition or electronic throttle override). Torsen diffs reduce the incidence of such wheelspin by transferring torque to the opposite drive wheel. Other types do the same by braking the spinning wheel against the gripping drive wheel by clutch friction. The main difference is the clutch type can lock a wheel that has little to no grip against a wheel that still has grip. Torsen cannot. Either way the diff reduces or eliminates the traction control effect until both wheels spin up. The Torsen initially brakes only the wheel with little or no grip until the other wheel also starts to spin up. Clutch type do not detect any wheelspin up until the gripping wheel also spins up. In theory if your clutch type LSD was loose enough it would not operate if traction control were active. In practice the LSD preload is enough.

Stability control is mainly affected by steering angle sensor input as compared by the computer to the internal yaw sensor input, yaw sensor is usually found in the trunk. Again, tire grip and chassis characteristics don't really matter to the software. All stability control software uses similar software to traction control. The one diff (har har) is integrating an electronic or torque vectoring diff such as the one fitted to the QV. That requires additional output capability.

The main challenges to developing either system was slow computers. Brakes can easily develop over 1,000 HP (one reason those unintended acceleration cases could not actually have happened) and the necessary precision modulation of that kind of power to balance overenthusiastic throttle application was tricky to achieve. Really good abs allowed it to happen. Really fast and small computers were needed. Stability control uses the same output controls as the traction control which is why it was relatively simple to add it to traction control.
 

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It is just a common sense to turn ESC off when stuck in a snow, sand or mud to allow the wheel spin. If the driver is not acknowledgement how to drive in a snow/sand/mud/ice he/she should take driving courses again
Well, yes and no. Non expert drivers would be wise not to try that. Modern traction and stability control offer far superior vehicle control to that within the capability of a driver using only common sense.

I live where extreme driving conditions are part of my daily drive for half the year. Only very, very occasionally is it advantageous to switch off the electronic traction or stability controls in snow and never on glare ice. For wheelspin to be effective in snow you must also have the correct type of snow tire. Ordinary tires are useless when spinning in snow or on ice. Even high performance snow tires are less effective when spinning. Full on winter tire tread is needed. Even then you need exceptionally precise throttle control to beat traction control. You must control wheelspin to a very low level for a winter tire to chew its way out of being stuck. I cannot overemphasize just how tricky it is to achieve the necessary throttle control to perform this task. My cars with traction control each also have a less aggressive setting to assist the driver in achieving this level of wheelspin control. The one on my Jaguar is excellent. The one on my Subaru BRZ not so much.

Jaguar has just developed an extreme conditions traction control better than any driver, probably by adapting Land Rover's hill descent control software. I don't think you'd switch that off if stuck in snow or mud.

Del wil love this: you really need a clutch to beat all low friction surfaces.

Bottom line, if you drive an automatic leave traction control fully on in very slippery conditions. Use the Winter button, that's why it's there.
 

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Michael, it is written in owners manual for FCA cars to switch off the traction control in a case of using chains or stuck in mud/snow etc...
The software will not allow to spin tires, so the car is unable to move.
I always turn off ESC here in Calgary in a heavy snow or on ice :) Driving conditions here are not extreme, just winter driving. The snow here is dry, like a powder, so the roads are not covered by ice. They still have a lot of traction. The worst case scenario I had in Ukraine was a wheel spin at 1100 rpm at 50 km/h on new Gislaved tires.

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Well, yes and no. Non expert drivers would be wise not to try that. Modern traction and stability control offer far superior vehicle control to that within the capability of a driver using only common sense.
the traction control systems are nowadays quite good, the 1st solutions were worse, for example my ex 156 had some problem with certain type of snow, but in most conditions it was working ok. Stability control was very good in 156, it gave some free before taking any actions.
 

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Michael, it is written in owners manual for FCA cars to switch off the traction control in a case of using chains or stuck in mud/snow etc...
The software will not allow to spin tires, so the car is unable to move.
I always turn off ESC here in Calgary in a heavy snow or on ice :) Driving conditions here are not extreme, just winter driving. The snow here is dry, like a powder, so the roads are not covered by ice. They still have a lot of traction. The worst case scenario I had in Ukraine was a wheel spin at 1100 rpm at 50 km/h on new Gislaved tires.

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You're in Calgary (oops, of course you are, I just forgot)? In my opinion we get the most difficult (I.e severe) winter conditions of anywhere due to the temperature changes.

The only time I switch traction control completely off in slippery conditions is if I am actually stuck and unable to drive out. Usually that doesn't work either. My awd Jaguar just doesn't get stuck. My BRZ is just hopeless and I suspect the very high TBR Torsen diff is to blame for that.

If Alfa has no partial "off" for its traction control it needs to revisit that. All base Giulias sold in Calgary are to be awd and assuming it's the same system used by Jaguar traction control won't need to be switched off. Indeed, unless you leave traction control at least partially active Jaguars awd system is actually a two wheel drive system. Alfa will be the same.
 

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We almost do not have rains in -5, when all surfaces, even car door handles are covered by 1-2cm ice. We almost do not have fogs in -20, we do not have wet snow that became an ice in 1-2 hours. Our roads are good, without 20cm deep potholes. We do not use military trucks to help stuck on ice buses :) Driving conditions here in Calgary are almost perfect :)

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We almost do not have rains in -5, when all surfaces, even car door handles are covered by 1-2cm ice. We almost do not have fogs in -20, we do not have wet snow that became an ice in 1-2 hours. Our roads are good, without 20cm deep potholes. We do not use military trucks to help stuck on ice buses :) Driving conditions here in Calgary are almost perfect :)

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I've lived here for more than 40 years. All of the events you describe have occurred in Calgary except military trucks used as tow trucks. We use more modern big rig tow trucks than the Canadian Armed Forces can afford to tow buses. Saw it done just three years ago.
 

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Simples. Put a Torsen equipped car on a road surface with one wheel on ice and the other on dry Tarmac and the Torsen equipped car will simply spin up the wheel on ice. I know this because I drive one. The BRZ has a Torsen and is useless on snow or ice.

Put an identical car on the same surface combination but equipped with an LSD and the differential will limit (eliminate actually) the slip from the wheel on ice and move off.

I know Wikipedia and other sources describe Torsen diffs as LSD but they are not. The manufacturers of Torsen or helical type diffs all describe them accurately as torque biasing (or torque sensing, the origin of the trade marked name for the original Gleason type). For a Torsen to limit wheelspin there must be torque applied to the spinning wheel. Which is why you need traction control as well as a Torsen for that to work in slippery weather, although knowledgable but ancient drivers will just apply a little handbrake and drive off. Torsen have many advantages but limiting slip isn't one of them.

Failure to understand the completely different performance capabilities of LSD as compared to Torsen can lead to disappointment when the Torsen fails to limit wheelspin.

As for a Torsen limiting wheelspin due to body roll effects, nocando. Besides, live axles develop wheelspin from the right hand wheel due to torque reaction effects, regardless of springing, roll bars, damper rates or weight distrubuition front to rear. Putting the driver on the right hand side of the car helps though.
that are absolutely a limited slip. just because they react and behave differently than the classic clutch type LSD dosent mean they are not. if torque biasing its the term use than a clutch type does that too by sending biasing power to the other axle via clutch disc. that is the function of the disc and ramps.

im pretty sure i there is no misunderstanding on my part. many of my fwd circuit racers friends have swapped their torsen out for a traditional clutch diff because of the unpredictability of the airborne wheel when clipping the high curbs. ive ice lake autocross a torsen optioned miata and the thing was hopeless and can barely get moving much like you have described. having said that, a torsen its still a limited slip diff... just different type with different attribute and shortcomings.

im not sure why you are fixated on its behavior on the frozen tundra of the great white north? a torsen application for sports cars, or wide R compound performance tires, low air dams, soft tops, etc arent great for the winter. one should drive a SUV if thats a concern.

amongst all the technical jargon you have you have shared here, I will ask you once again, what is the function or a torsen then? I believe you refusal to answer this lies the answer to this debate.

all the best
 

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that are absolutely a limited slip. just because they react and behave differently than the classic clutch type LSD dosent mean they are not. if torque biasing its the term use than a clutch type does that too by sending biasing power to the other axle via clutch disc. that is the function of the disc and ramps.

im pretty sure i there is no misunderstanding on my part. many of my fwd circuit racers friends have swapped their torsen out for a traditional clutch diff because of the unpredictability of the airborne wheel when clipping the high curbs. ive ice lake autocross a torsen optioned miata and the thing was hopeless and can barely get moving much like you have described. having said that, a torsen its still a limited slip diff... just different type with different attribute and shortcomings.

...

amongst all the technical jargon you have you have shared here, I will ask you once again, what is the function or a torsen then? I believe you refusal to answer this lies the answer to this debate.

all the best
You have answered your own question, apparently unwittingly.

Jack up one drive wheel of a Torsen equipped car and note that no limited slip function exists. (It is possible to build a clutch type LSD that also won't limit slip at zero traction but almost if not all include a spring loaded preload to prevent this from happening. )

The reason curb hopping can cause difficulties for drivers of Torsen equipped cars is because the Torsen cannot limit differentiation. Once a driven wheel loses all traction, as it may when bounced over a curb, the Torsen is completely open. This is completely predictable but inexpert drivers can be caught off guard. The Torsen equipped car operates exactly as if it had an open diff while curb jumping, easy to drive. Changing out to a clutch type does not improve the predictability. On the contrary, with a curb hopping LSD equipped car the inside wheel will lock as it bounces upwards and then provoke an oversteer moment immediately followed by ndersteer as soon as it touches down again. Maybe faster lap times are possible although I am sceptical about that. Torsen equipped cars will simply slow a little as the inside drive wheel bounces, all nice and predictable.

A Torsen only biases the torque split up to a maximum ratio ( the torque bias ratio or TBR). It can only do so by dividing the minimum torque reaction available at either of the two drive wheels unequally by the TBR. The non reversing characteristic of worm gears allows differentiation in one direction only which is how the torque gets split unequally. I admit to great difficulty visualizing this differentiation action and I suspect most people less ingenious than Gleason also have this difficulty. There are a number of very good videos out there which make it easier to understand.

Whether biasing or not the Torsen always allows differentiation without resistance across the diff so, by definition, cannot limit slip between the two drive axles.

A clutch type LSD works by braking the wheel that has insufficient torque reaction against the other drive wheel across the diff. This type of diff resists differentiation up to the locking point when no differentiation occurs, limiting slip and then eliminating slip. This never happens in a Torsen.

Which you prefer depends on what you require. LSD are noisy, tricky to drive and subject to quite limited lifespan if used to reduce slip. Torsen are easy to drive, they drive as an open diff, and hardly wear at all and while differentiating they do not wear any faster than open diffs, probably less because some wear is transferred to the tires due to torque biasing.

Generally speaking a Torsen is preferred for road use. A clutch type LSD is completely inappropriate for fwd axles for obvious reasons, not the least of which is the steering angle locks when the diff locks.

Why Alfa chose a relatively obsolete LSD is a mystery unless they noticed it would fit into the same space as the nifty electronically modulated torque vectoring type fitted to the Giulia. Torsen biases torque automatically but cannot "torque vector" as that term is now used. To vector torque you need the capacity to overspeed the outside drive wheel which can only be done with some sort of clutch, usually in conjunction with a planetary overdrive. Very heavy and prone to overheating. Of dubious value in a road car also.
 
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