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      03-21-2013, 03:50 PM   #89
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Quote:
Originally Posted by walile View Post
Incorrect.

AWD will reduce the chance of hydroplaning in this scenario. Power is distributed between both axles, so the rear wheels are less likely skid under power.

The xDrive performs better in low traction conditions, there really isn't much room to debate on that.
Ok you do know what happens when you hydroplane right? It occurs when a tire rolls over a wet surface and is unable to evacuate the water quick enough which results in the tire "floating" over the water. This is a NO traction situation.

Look I am not putting down xDrive, I own a 335i xDrive and think its great. But I also run snow tires during winter because I know handling/braking traction is 95% in the tires and not in the drivetrain. I just can't stand how BMW has marketed xDrive as being advantageous in the wet. At the very best it only has a marginal advantage.
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      03-21-2013, 03:50 PM   #90
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Originally Posted by drob23 View Post
I'm no expert on hydroplaning, but I'd assume putting *any* power to the front wheels will reduce the ability to control the vehicle, since you are lowering available lateral tractive force.
But the rear wheels can lose traction first under power. Don't forget that. Imagine if a driver is driving a powerful RWD car in low traction conditions. Say he wanna pass the car in front of him and decided to steer and apply full throttle. Idiot move but hey people do that.

With no TC/ESP, he can oversteer and spin.

With TC/ESP, hopefully the system will intervene and cut power before he kills himself. Note that ESP is a passive system and slows you down.

With a good AWD system, some power is shifted to the front to prevent the rear wheel from losing traction. Again, AWD actively provides more traction. Definitely provides more performance headroom.

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Originally Posted by drob23 View Post
Regardless, the way the vehicle will deal with this is with the stability control system which will attempt to brake certain wheels. The drivetrain will not be responsible for redistributing force to counter the loss of yaw control. In either case the best thing you can do to prevent/recover is to not apply any throttle at all.
Again, ESP are passive systems. They save you from wrapping around a tree, but they cannot provide you with more traction. AWD gives you more traction from a standing still, as well as when you are moving.

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Originally Posted by drob23 View Post
The F30 definitely will torque vector, just with the brakes rather than drivetrain. Not great in a racing situation, but in terms of safety you don't really lose anything.
I don't remember torque vectoring being mentioned anywhere in the brochure. There is a eLSD function that simulate the function of a LSD, but that's no torque vectoring.
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      03-21-2013, 04:07 PM   #91
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Originally Posted by Accelerometer View Post
Ok you do know what happens when you hydroplane right? It occurs when a tire rolls over a wet surface and is unable to evacuate the water quick enough which results in the tire "floating" over the water. This is a NO traction situation.

Look I am not putting down xDrive, I own a 335i xDrive and think its great. But I also run snow tires during winter because I know handling/braking traction is 95% in the tires and not in the drivetrain. I just can't stand how BMW has marketed xDrive as being advantageous in the wet. At the very best it only has a marginal advantage.
I drive on proper winter tires, too. There is no substitute for that, after all your tires are the only thing that's touching the ground.

I also agree that if you find yourself driving on a sheet of ice where there is absolutely zero traction, then AWD and RWD will in theory be both the same. That is, you have zero control.

But the reality for many people live up North is that they gonna find themselves in low traction conditions quite often, whether it's rain or snow. The advantage of xDrive simply cannot be ignored.

It is fun to drift around, if I really wanna do that I will get myself a FR-S/BRZ with a proper LSD. For day to day driving, I will gladly take the xDrive over RWD. But that's because I don't live in California or Florida.
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      03-21-2013, 04:29 PM   #92
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Quote:
Originally Posted by walile View Post
But the rear wheels can lose traction first under power. Don't forget that. Imagine if a driver is driving a powerful RWD car in low traction conditions. Say he wanna pass the car in front of him and decided to steer and apply full throttle. Idiot move but hey people do that.

With no TC/ESP, he can oversteer and spin. With TC/ESP, hopefully the system will intervene and cut power before he kills himself. Note that ESP is a passive system and slows you down.
While I certainly won't disagree that AWD can appropriate less torque to the rear wheels, the culprit in this scenario is providing too much input. Whether this is steering or throttle, the driver is the one inducing the loss of control. The affect of AWD, especially a reactive system like xdrive, will be pretty marginal compared to the timescales ESP is able to actuate at. Even a torque sensing AWD system like quattro will likely do little to mitigate hydroplaning.

An interesting exercise in understanding the understeer/oversteer dependency on throttle input involves driving in a very tight circle at high speed. You can actually change the radius of your circle by applying throttle more/less. This works regardless of drivetrain.

Quote:
Originally Posted by walile View Post
With a good AWD system, some power is shifted to the front to prevent the rear wheel from losing traction. Again, AWD actively provides more traction. Definitely provides more performance headroom.
Yes, I definitely agree with this. But one must also understand there is a difference between (a) "predicatable" scenario where torque appropriation needs to shift - such as launching the car from a stop, or WOT when cornering; (b) unpredictable scenario such as ice on front tires, which requires either sensors to detect it or torque sensing in the differential (torsen for ex).

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Originally Posted by walile View Post
I don't remember torque vectoring being mentioned anywhere in the brochure. There is a eLSD function that simulate the function of a LSD, but that's no torque vectoring.
I'll look for it and post the link...
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      03-21-2013, 05:10 PM   #93
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Originally Posted by drob23 View Post
The affect of AWD, especially a reactive system like xdrive, will be pretty marginal compared to the timescales ESP is able to actuate at.
It is not entirely correct to call the xDrive a "reactive" system. While the xDrive system reacts and redistributes power according to the information from the sensors and driver inputs, it is technically an active system.

This is how it is defined. With an active AWD system or any active differential, torque delivery can be varied at will usually via a computer controlled clutch. So, Haldex based VW/Audi will be considered as an active system. The new active rear diff in the F10 M5 and C7 Corvette are other examples.

The Torsen based VW/Audi system or other viscous coupling based systems on the other hand are considered as passive. Because there are no means to actively control torque distribution via computer programming. Power distribution is varied when wheel slippage occurs.

Of course with Audi you can also have a passive Torsen center diff coupled with an active rear diff.

While you go look for mentions of torque vectoring on the f30, check out this video on xDrive as well. Both the blonde and brunette cute.

http://www.bmwusa.com/Standard/Conte...ng/xDrive.aspx
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      03-21-2013, 05:24 PM   #94
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Quote:
Originally Posted by walile View Post
It is not entirely correct to call the xDrive a "reactive" system. While the xDrive system reacts and redistributes power according to the information from the sensors and driver inputs, it is technically an active system.

This is how it is defined. With an active AWD system or any active differential, torque delivery can be varied at will usually via a computer controlled clutch. So, Haldex based VW/Audi will be considered as an active system. The new active rear diff in the F10 M5 and C7 Corvette are other examples.

The Torsen based VW/Audi system or other viscous coupling based systems on the other hand are considered as passive. Because there are no means to actively control torque distribution via computer programming. Power distribution is varied when wheel slippage occurs.

Of course with Audi you can also have a passive Torsen center diff coupled with an active rear diff.

While you go look for mentions of torque vectoring on the f30, check out this video on xDrive as well. Both the blonde and brunette cute.

http://www.bmwusa.com/Standard/Conte...ng/xDrive.aspx
I suppose your definition of active is probably better, whereas mine is more in regards to how the torque split is optimized. In the case of xdrive you have an electronic control system, which filters sensor measurements in conjunction with driver inputs and uses a plant model to calculate actuator inputs, which in this case goes to the clutch pack. Thus, it is a combination of a feed-forward and feedback control system. The actuator input commands are limited with respect to dynamic response to reject noise from the sensors. You can generally sense this bandwidth limitation with xdrive/haldex, where the car powertrain seems to "change" once you start to hit a different surface.

On the other hand, a torque sensing differential, ie conventional limited slip differential, uses a mechanical gear set to optimize torque appropriation. There is no limitation on the actuator bandwidth other than the physics of the coupling mechanism (viscosity for example). These systems will provide optimum torque distribution in terms of maximum traction. On the other hand, one cannot enforce constraints such as: force all torque to the rear wheels, which might reduce understeer in certain instances.

Side - I don't think either the M5 nor C7 have active rear differentials. Only Audi, Lancer Evo, Acura SH-AWD, Nissan Nismo stuff and BMW x5m-x6m-x6 as far as I can tell
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      03-21-2013, 06:17 PM   #95
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Quote:
Originally Posted by drob23 View Post
I suppose your definition of active is probably better, whereas mine is more in regards to how the torque split is optimized. In the case of xdrive you have an electronic control system, which filters sensor measurements in conjunction with driver inputs and uses a plant model to calculate actuator inputs, which in this case goes to the clutch pack. Thus, it is a combination of a feed-forward and feedback control system. The actuator input commands are limited with respect to dynamic response to reject noise from the sensors. You can generally sense this bandwidth limitation with xdrive/haldex, where the car powertrain seems to "change" once you start to hit a different surface.

On the other hand, a torque sensing differential, ie conventional limited slip differential, uses a mechanical gear set to optimize torque appropriation. There is no limitation on the actuator bandwidth other than the physics of the coupling mechanism (viscosity for example). These systems will provide optimum torque distribution in terms of maximum traction. On the other hand, one cannot enforce constraints such as: force all torque to the rear wheels, which might reduce understeer in certain instances.

Side - I don't think either the M5 nor C7 have active rear differentials. Only Audi, Lancer Evo, Acura SH-AWD, Nissan Nismo stuff and BMW x5m-x6m-x6 as far as I can tell
I did not come up with the definition of active and passive differential. It's the industry standard and about as clear cut as the difference between an open diff and LSD.

The new M5 definitely has an active rear diff. Based on the press release available, the C7 will sport an active rear diff as well.

http://www.bimmerfile.com/2011/09/28...ial-in-detail/

Frankly, I don't know if you really know what you are talking about here. You don't know the fundamental difference between active and passive awd systems. Then you try to say that a Torsen based system is superior, how is that relevant to the rwd vs xdrive discussion here?

I will leave you this to ponder, if a passive Torsen diff is truly superior then why does Audi use an active rear diff today (namely the Sport Differential) instead of a Torsen rear diff like they did back in the late 80s?
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      03-21-2013, 06:48 PM   #96
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Quote:
Originally Posted by walile View Post
I did not come up with the definition of active and passive differential. It's the industry standard and about as clear cut as the difference between an open diff and LSD.
Fair enough, I'm not going to argue semantics. I never called anything passive, so I'm not sure why you're saying that. I said "reactive".

Quote:
Originally Posted by walile View Post
The new M5 definitely has an active rear diff. Based on the press release available, the C7 will sport an active rear diff as well.

http://www.bimmerfile.com/2011/09/28...ial-in-detail/
You are right, I read wikipedia and read the e39 instead of F10. Didn't know that about C7.

Quote:
Originally Posted by walile View Post
Frankly, I don't know if you really know what you are talking about here. You don't know the fundamental difference between active and passive awd systems. Then you try to say that a Torsen based system is superior, how is that relevant to the rwd vs xdrive discussion here?
Alright buddy, feel free to take pot shots at me. Not sure where I fail to understand the difference. I was explaining a reactive system...but clearly you don't care, so forget it.

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Originally Posted by walile View Post
I will leave you this to ponder, if a passive Torsen diff is truly superior then why does Audi use an active rear diff today (namely the Sport Differential) instead of a Torsen rear diff like they did back in the late 80s?
Simple...rear diff eliminates understeer as it uses a feed forward control structure. You can easily anticipate torque appropriation based on inputs regardless of disturbances. The purpose of the center differential is to maximize traction regardless of performance, the only way to improve performance is to increase the rear bias via changing the nominal gearing. And Audi uses the crown center differential, not a torsen (which cannot self lock).
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      03-21-2013, 08:39 PM   #97
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I often find that debating on Internet forums is a waste of time. Yet I also don't want people to come here and get misinformed or think that this forum lacks fundamental automotive knowledge. Nothing personal here.

Now, just because you make a statement, that doesn't make it true. What you are saying simply does not make sense.

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Originally Posted by drob23 View Post
Simple...rear diff eliminates understeer as it uses a feed forward control structure. You can easily anticipate torque appropriation based on inputs regardless of disturbances.
It's not the "rear diff" part that eliminates understeer, after all every modern cars have a rear differential.

Of course it's the torque vectoring that reduces the understeer, and its implementation necessitates a computer controlled active differential or using rear brakes like Porsche. In theory you can have a front active diff with torque vectoring on a FWD car.

Quote:
Originally Posted by drob23 View Post
The purpose of the center differential is to maximize traction regardless of performance, the only way to improve performance is to increase the rear bias via changing the nominal gearing.
What is the "Regardless of performance" nonsense? In an AWD system, the goal is to maximize the use of available traction to yield higher performance. They are directly related.

Increase rear bias is only beneficial if there are more traction at the rear. Otherwise we will just send 100% of the power to the rear aka RWD.

Quote:
Originally Posted by drob23 View Post
And Audi uses the crown center differential, not a torsen (which cannot self lock).
You are correct that on some model like the RS5 it uses the new crown gear center diff. But I don't know if that change has trickled down to their entire model lineup.

It also doesn't change the fact that it is not an active center differential. So, it cannot proactive change power distribution as soon as it senses steering input. Of course when coupled with the active Sport Differential at the rear, it becomes less of an issue.
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      03-21-2013, 08:47 PM   #98
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Originally Posted by drob23 View Post
Simple...rear diff eliminates understeer as it uses a feed forward control structure.
Also got some homework for you.

1. Please describe the system and explain why it is a feed forword control structure. List the input, output, and disturbance to the system.


2. If an active rear differential uses feed forward control structure, then does an active center differential also employ feed forward control? Why or why not?
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      03-21-2013, 08:59 PM   #99
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Quote:
Originally Posted by walile View Post
I often find that debating on Internet forums is a waste of time. Yet I also don't want people to come here and get misinformed or think that this forum lacks fundamental automotive knowledge. Nothing personal here.

Now, just because you make a statement, that doesn't make it true. What you are saying simply does not make sense.
Please point out all of my logical fallacies, all I read is you preaching superior intellect and knowledge.


Quote:
Originally Posted by walile View Post
It's not the "rear diff" part that eliminates understeer, after all every modern cars have a rear differential.
ok the rear ACTIVE differential!!!! Read between the lines...christ...

Quote:
Originally Posted by walile View Post
Of course it's the torque vectoring that reduces the understeer, and its implementation necessitates a computer controlled active differential or using rear brakes like Porsche. In theory you can have a front active diff with torque vectoring on a FWD car.
Torque vectoring is a principle of physics, it can be done with brakes or throttle. You are arguing which one of my points?


Quote:
Originally Posted by walile View Post
What is the "Regardless of performance" nonsense? In an AWD system, the goal is to maximize the use of available traction to yield higher performance. They are directly related.

Increase rear bias is only beneficial if there are more traction at the rear. Otherwise we will just send 100% of the power to the rear aka RWD.
Increasing torque to the front wheels reduces the ability to turn the car. This is simple physics, there are situations where you want traction for cornering rather than power application. Again, you read what you want and completely miss the point. I said that the crown/torsen center differential appropriates torque based purely on minimizing wheel slip, not optimizing for track times or whatever metric you want to consider. I was talking about a torsen/crown center diff, not any general AWD system.

Quote:
Originally Posted by walile View Post
You are correct that on some model like the RS5 it uses the new crown gear center diff. But I don't know if that change has trickled down to their entire model lineup.
I have it on my S4.

Quote:
Originally Posted by walile View Post
It also doesn't change the fact that it is not an active center differential. So, it cannot proactive change power distribution as soon as it senses steering input. Of course when coupled with the active Sport Differential at the rear, it becomes less of an issue.
Fantastic, what's your point?
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      03-21-2013, 09:26 PM   #100
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Quote:
Originally Posted by walile View Post
Also got some homework for you.

1. Please describe the system and explain why it is a feed forword control structure. List the input, output, and disturbance to the system.


2. If an active rear differential uses feed forward control structure, then does an active center differential also employ feed forward control? Why or why not?
Thanks professor!

Here you go

1) It is a feed forward control system because it does not need to track reference signals. The system is not unstable to begin with, thus it can be appropriately tuned open loop.

driver input y_1 = [SWA; throttle] sensor y_2 = [vel; yawRate]

measurement y = [y_1; y_2]

input u = [torque R/L]

disturbance d = n/a

It's actually an open-loop controller because there really is no disturbance. Mitsu is the only company I'm aware of that tries to track a reference yaw rate, so it can be done closed loop. It takes some kind of nonlinear combination of the ABS, active center diff and rear active diff.

2) The center diff uses a combination of feed forward and feedback control. The feed forward component functions similar to sports rear diff, when you mash the gas (torque goes rear) or turn the wheels (torque goes rear), torque will be appropriated as needed.

On the other hand, the most worrisome disturbance it rejects is the loss of tractive force. This is not know a priori, there is no knowledge of when the road will be slick, this can only be calculated by the vehicles stability control system which employs a Kalman Filter to estimate wheel slip through ABS sensors. The center diff receives this information via CAN.
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      03-21-2013, 10:55 PM   #101
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Quote:
Originally Posted by drob23 View Post
Thanks professor!

Here you go

1) It is a feed forward control system because it does not need to track reference signals. The system is not unstable to begin with, thus it can be appropriately tuned open loop.

driver input y_1 = [SWA; throttle] sensor y_2 = [vel; yawRate]

measurement y = [y_1; y_2]

input u = [torque R/L]

disturbance d = n/a

It's actually an open-loop controller because there really is no disturbance. Mitsu is the only company I'm aware of that tries to track a reference yaw rate, so it can be done closed loop. It takes some kind of nonlinear combination of the ABS, active center diff and rear active diff.

2) The center diff uses a combination of feed forward and feedback control. The feed forward component functions similar to sports rear diff, when you mash the gas (torque goes rear) or turn the wheels (torque goes rear), torque will be appropriated as needed.

On the other hand, the most worrisome disturbance it rejects is the loss of tractive force. This is not know a priori, there is no knowledge of when the road will be slick, this can only be calculated by the vehicles stability control system which employs a Kalman Filter to estimate wheel slip through ABS sensors. The center diff receives this information via CAN.
First of all, I sincerely apologize to everyone for

I have to be honest, I went out for a Tim Hortons coffee and comeback impressed. Makes me wonder if it's the same person. Just want to point out that

- There is at least one active rear differential implementation that track reference signals but the control algorithm is very tightly coupled with the entire AWD system and it's not Mitsubishi. I think we can agree that you can have both feed forward and feed forward + feedback design.

If Audi Sport Differential is a simple feed forward system, to be honest I am surprised. At this day and age, it seems a bit primitive. But then again, it doesn't have active center diff to dance with. Might as well KISS.


- I philosophically disagree with the Porsche implementation. Braking system IMHO should be used for reducing vehicle speed or ESP applications, not to help it go faster! Even though I do acknowledge some advantages of that design. Namely the cost and weight saving.


- We certainly have a fundamental philosophical disagreement on system design.

To me, a Torsen or crown gear based system is both primitive and inferior. Sure it's the feed-forward control design that you love so much. But what it really is saying is that hey all the behaviors of the system is programmed mechanically into the design and is passive in its nature.

As you pointed out yourself that ideally you want less power to the front wheels during corning. Well, can the Audi system proactively shift more power to the rear as steering input is detected? NO!

The GTR ATTESA E-TS is an incredible system, certainly did not archive such incredible performance using a simple feed-forward design.
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      03-21-2013, 11:20 PM   #102
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Quote:
Originally Posted by walile View Post
First of all, I sincerely apologize to everyone for

I have to be honest, I went out for a Tim Hortons coffee and comeback impressed. Makes me wonder if it's the same person.
Well thanks for your approval and the backhanded complement.

Quote:
Originally Posted by walile View Post
Just want to point out that

- There is at least one active rear differential implementation that track reference signals but the control algorithm is very tightly coupled with the entire AWD system and it's not Mitsubishi. I think we can agree that you can have both feed forward and feed forward + feedback design.
Go read this

Quote:
Originally Posted by walile View Post
If Audi Sport Differential is a simple feed forward system, to be honest I am surprised. At thisday and age, it seems a bit primitive. But then again, it doesn't have active center diff to dance with. Might as well KISS.

- I philosophically disagree with the Porsche implementation. Braking system IMHO should be used for reducing vehicle speed or ESP applications, not to help it go faster! Even though I do acknowledge some advantages of that design. Namely the cost and weight saving.

- We certainly have a fundamental philosophical disagreement on system design.
Simpler is better if the purpose is served, since you are such an expert on control systems, what do you recommend auto makers do? Do you realize how complex the interconnections are, and the fault mechanisms built into CAN? The cost constraints for a mass produced/low margin product are not trivial.

Quote:
Originally Posted by walile View Post
To me, a Torsen or crown gear based system is both primitive and inferior. Sure it's the feed-forward control design that you love so much. But what it really is saying is that hey all the behaviors of the system is programmed mechanically into the design and is passive in its nature.

As you pointed out yourself that ideally you want less power to the front wheels during corning. Well, can the Audi system proactively shift more power to the rear as steering input is detected? NO!
You have been putting *a lot* of words into my mouth. The torsen is NOT feed forward, what are you talking about? I pointed out that a torsen/mechanical center diff is better at minimizing wheel slip as it does not require any estimation, it just does it. I never said it was better in corners or anything of that nature. Previous versions of Audi vehicles have suffered from understeer horribly. First change was to increase nominal gearing to 40-60, now they have included active rear diff. More torque will naturally go to the rear wheels when accelerating because the vehicle will pitch backwards and there will be more available tractive force. Electronic center diffs are more useful for rally racing, where wheels can go off the ground.

Quote:
Originally Posted by walile View Post
The GTR ATTESA E-TS is an incredible system, certainly did not archive such incredible performance using a simple feed-forward design.
Huh, wtf does this have to do with feed forward design? The GT-R is built from the ground up to be a race car and the control system is necessarily very advanced and highly tuned. This is not the same system as xdrive which comes on a 320ix 32k car. You pay *a lot* of money to maintain this cars drivetrain.
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      03-21-2013, 11:58 PM   #103
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Go xDrive!
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      03-22-2013, 12:04 AM   #104
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Here in "Northern Canada" I would never buy a vehicle without AWD. Add some dedicated snow tires and some driving skill and that's all you need. I still can't believe I am selling my Legacy GT and buying an F31. If the BMW is 2/3 as good as my Subarus in the snow I will be happy.
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      03-22-2013, 06:30 AM   #105
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Quote:
Originally Posted by drob23 View Post
Well thanks for your approval and the backhanded complement.

Go read this

Simpler is better if the purpose is served, since you are such an expert on control systems, what do you recommend auto makers do? Do you realize how complex the interconnections are, and the fault mechanisms built into CAN? The cost constraints for a mass produced/low margin product are not trivial.

You have been putting *a lot* of words into my mouth. The torsen is NOT feed forward, what are you talking about? I pointed out that a torsen/mechanical center diff is better at minimizing wheel slip as it does not require any estimation, it just does it. I never said it was better in corners or anything of that nature. Previous versions of Audi vehicles have suffered from understeer horribly. First change was to increase nominal gearing to 40-60, now they have included active rear diff. More torque will naturally go to the rear wheels when accelerating because the vehicle will pitch backwards and there will be more available tractive force. Electronic center diffs are more useful for rally racing, where wheels can go off the ground.

Huh, wtf does this have to do with feed forward design? The GT-R is built from the ground up to be a race car and the control system is necessarily very advanced and highly tuned. This is not the same system as xdrive which comes on a 320ix 32k car. You pay *a lot* of money to maintain this cars drivetrain.
At the end of the day, feel free to believe whatever you want. Our discussion has gone well beyond the scope of whether to opt for xDrive or not. The trend of AWD system design definitely lean towards active differential and why not? On an ESP equipped vehicle, you have all the sensors in place already. Computing power is cheap these days. Sure R&D cost money but that's how I get paid.

Given the current state of affair, more performance can be extracted with an active differential whether it is placed at the front, center, or rear. Which is why I mentioned GT-R. It simply finds more grip than your beloved "feed forward control" passive design. Shame that earlier GTR had transmission made out of glass and even today a switch on the dash dedicated to void your warranty.

A notable exception to this trend by the way is the 2014 AMG E63 4matic. Which is as KISS as it gets. It will be interesting to see how much benefit a simple AWD system brings to that beast, and how BMW reacts for that matter. I certainly hope that BMW do more than just try to set a new drift record with the M5.

Oh and with the GT-R, cost of differential fluid is not that bad, it's the transmission fluid that kills you. The late model Lancer Evo, incidentally the topic focus of the article you linked to, require scheduled diff fluid change just the same, though perhaps the cost is not as outrageous.
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      03-22-2013, 07:18 AM   #106
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X drive is worth it on snow but sucks having higher ride height when cornering. I got a killer deal on my fully loaded 2013 335xi sedan or else id have gotten the DHP option
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      03-22-2013, 09:20 AM   #107
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It simply finds more grip than your beloved "feed forward control" passive design.
Ok, at this point I have to concede that you sir have no idea what you're talking about. Feel free to continue to read wikipedia and police the internet forums of this world with your vast knowledge. Good day!
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      03-22-2013, 10:21 AM   #108
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We had a pretty harsh winter here in New England, and I didn't have any issue with my M3 on blizzaks. I have never got stuck!
I would never drive an xdrive, not because of the weight, but because of the steering feeling. There is a reason why M cars don't come with AWD
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      03-22-2013, 10:31 AM   #109
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We had a pretty harsh winter here in New England, and I didn't have any issue with my M3 on blizzaks. I have never got stuck!
I would never drive an xdrive, not because of the weight, but because of the steering feeling. There is a reason why M cars don't come with AWD
That's a good looking M3, please tell me you keep it garaged, could never imagine parking that in Cambridge. I bet the M3 is actually easier to control in the snow then one might think, not lots of low end torque?

Isn't the next M5 rumored to have AWD?
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      03-22-2013, 10:37 AM   #110
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That's a good looking M3, please tell me you keep it garaged, could never imagine parking that in Cambridge. I bet the M3 is actually easier to control in the snow then one might think, not lots of low end torque?

Isn't the next M5 rumored to have AWD?
Thank you!
Yep, I have indoor parking, and I never park it on street. M3 is easy to control mostly thanks to LSD I guess... If you are calm, and treat the throttle well you won't have any issue.
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