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Discussion Starter · #1 ·
I wasn't really fussed about this, until I read a post by someone on Pistonheads:

I'm not sure how the system works on the Duster, but for off road it's not about stability, but promoting grip. The difference is off road you don't want it to kill power, all you want it to do is brake a spinning wheel to force it to apply load to the one not spinning, but you want to retain control of the throttle.

For example:



With an open diff and no TCS the rear wheel off the ground would spin and the one on the ground would not move at all. With an IFS/IRS vehicle with not huge wheel travel picking a wheel up will be common off road.

An off road TCS will allow the wheel in the air to spin, but by braking it, it'll force the diff to send hp (due to the loading) to the wheel not spinning, forcing it to turn.

Where this is important is, if you had the diagonal front wheel in the air too (common off road, called an axle twister) then each wheel off the ground would spin, while the two on the ground wouldn't move and you'll be stuck.

Even with all wheels on the ground, if its loose or slippery then you may not get all 4 spinning, but rather you'll end up with 2wd, one wheel per axle being driven.

Locking diffs prevent this, but are expensive and potentially break things. They also ruin turning circles and can't be used at higher speed. Off road TCS is a brilliant invention and I'm pleased the Dacia can be had with this feature.

Interesting reading huh? Assuming this is all correct, it's a must have feature in a way.
 

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I believe the fact that this option is not available on the Access models is the main reason why the Duster did not score a higher NCAP safety rating, and it's a 'no brainer' option to choose.

Graham
 

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Discussion Starter · #3 ·
Well, it's not so much about the stability on road I'm fussed about, it's more the fact that if you go for the 4x4 version, because there is no manual locking diff, you essentially need this ASR option, which then bumps you up to mid-spec model...
 

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The system described by Nick and available on higher spec Dusters as an option is a form of ESC, electronic stability control. I'm not sure exactly how this particular system works but in general it is designed to detect loss of stability of the vehicle, for example during cornering or braking. It restores stability by applying individual brakes and in some versions by cutting engine power.
This system would not operate or help whilst manoeuvring slowly in difficult off-road situations where one or more wheels has lost traction. There is an electronic system that does this, known as ELD, electronic locking differential, I have it fitted to my Fiat Panda Cross though I haven't had a chance to test it out. It brakes wheels individually that have lost traction but uses different monitoring and computer systems from those used by ESC.
The bottom line is that ESC would not help restore traction in an off-road situation.
 

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ASR as an option on the Duster appears to work by reducing torque to a spinning wheel rather than braking that wheel. Hence it would not be of any use when a wheel lifted in an off road situation, or when cross-axled.
I learned to drive in a Triumph Herald. No electronic systems and a terrible rear axle set up that would produce oversteer at the drop of a hat. I like to think that I still retain the driving style required for that car and that I can live without ESC. Hence I'm quite happy that my Access model doesn't have ESC as an option.
 

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My understading is that the Duster's ESC / ASR option is aimed at improving stability under normal (road) driving conditions. It's the off-road mode of the ABS (which switches in when , "Lock" is selected) that helps with the diagonal spin problem commonly encountered off road.

Quoting the Driver's Handbook. - "When "4WD Lock" mode is active, the ABS switches to off-road mode. In this case, the wheels may lock intermittently to achieve better grip, thus reducing braking distances on soft ground."

The Handbook even goes as far as to say the ESP (=ESC?) should be switched off on soft ground etc.

Quote from the Handbook. - "When driving on soft ground (sand, mud, deep snow), we recommend that you deactivate the ESP function by pressing the "ESP" switch. In this case, only individual wheel braking remains active. This function applies the brake to any wheel that is slipping, allowing the engine torque to be transferred to the wheels with the most grip. This is particularly useful when crossing a bridge.

Do others agree with my understanding?

Chris
 

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So that confirms what I read on pistonheads. Speccing ASR is a must, if you're serious about going off-road. Welcome to the site by the way Chris
 

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Thanks for the welcome, Nick.

If my interpretation of the handbook is correct then the (optional) ESC / ASR actually hinders low speed off-road traction / diagonal spin control. Hence the recommendation to, ".......deactivate the ESP", in certain circumstances. It's the off-road function of the (standard) ABS that controls diagonal spin when, "4WD Lock", is selected.

As I inferred before, I'm not 100% sure I'm interpretting the handbook correctly though. (I suspect some things may have been lost in the translation - Reference to, ".....particularly useful when crossing a bridge", for instance!)

Chris
 

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I ordered the ESC and traxction control as I had read a similar thing about it helping off-roading. It was another thread on pistonheads, funnily enough.

However I have a agree with Chris' (welcome to the site Chris and Tony) interpretation of the handbook.

My only thoughts are that if Dacia are making such a thing of the Duster's off-road capability, they MUST have designed it to cope with the cross-axle spin.

Or is that just Naive?
 

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Thanks for the, "Welcome", TonyTheHat.

With regard to your comment, "My only thoughts are that if Dacia are making such a thing of the Duster's off-road capability, they MUST have designed it to cope with the cross-axle spin."

My understanding, based on the handbook, is that Dacia have designed the 4WD Duster to cope with the diagonal spin problem. But it's done using the standard ABS rather than the optional ESC / ASR.

(Althought I still worry about my interpretation of that Handbook!).

Chris
 

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Discussion Starter · #11 ·
It's based on the Nissan X-Trail system, so would they have just grabbed the entire system? I'll do a bit of digging to see what that comes up with,
 

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Hi, Nick - Thanks for offereing to dig.

I think I read somewhere that the Duster's system is based on a previous generation of the X-Trail. Just a thought as that might affect your research.

What we really need is a, "Tame", Dacia technical design person to explain this to us!

Chris
 

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Discussion Starter · #14 ·
Interesting. I couldn't tell much of a difference with it switched on and off. Could be because it was slowed down?
 

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Discussion Starter · #15 ·

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Nick,

Where on earth do you keep finding this stuff?!?!

I mean, Thanks
 
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Chris,

Think you are spot on, as this was in the PDF Nick uploaded;

'An Active Brake Limited Slip Differential, also controlled by the ABS sensors, applies the brakes to any wheel that has lost traction and, in so doing, transfers drive to the opposite wheel on the same axle.'

 

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Discussion Starter · #18 ·
Mainly Google and selective searching of other forums
 

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Well, thank you. You have put loads of intersting stuff on. I realy appreciate it.

I have spent hours surfing about the Duster. Given I have no car at present, not a lot else to do
.

Still have not managed to find as much info as you.

Keep it coming, LOL
 

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Many thanks, Nick.

The crucial part of that document (as far as our discussion on contolling diagonal spin is concerned) is the sentence highlighted by TonyTheHat.........

"An Active Brake Limited Slip Differential, also controlled by the ABS sensors, applies the brakes to any wheel that has lost traction and, in so doing, transfers drive to the opposite wheel on the same axle."

Let's hope Dacia incorporated that particular element of Nissan's system when, "Basing the Duster's 4WD system on the X-Trail"!

Chris
 
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