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Gtir Motorsport club » Tech room » Gearbox section » ATTESA AWD System

ATTESA AWD System

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1 ATTESA AWD System on 6th June 2017, 4:22 pm

typeritr

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So when looking online at GTI-R, I was looking into the 4wd system that the pulsar uses, I think Nissan stated that they use the ATTESA system in the pulsar that was used in the GT-R.

I searched this site for the info but couldn't find it.

Looking further into it some posts on different websites state it is 50/50 Front/Rear, mainly front, mainly rear etc... Load of people with opinions and no facts. So really cant find any decent information on it.

SO with that in mind can anyone tell me what system it uses?
Is it a real ATTESA that only engages the front when the rear loses grip?
Is it 100% of the time 50/50 front/rear?
Or is there some other differential type system that transfers power front and rear?

Now once the power is split front to back:
Is it then split 50/50 left/right?
Is it split 50/50 Left and Right through a limited slip differential? So the rear wheels have their own LSD to split the power left and right and the front wheels have their own LSD to split the power left and right. In essence all 4 wheels can be spinning at different speeds? Any explanation on this would be much appreciated as I would love to know how it works.

2 Re: ATTESA AWD System on 6th June 2017, 8:59 pm

gtir_woody

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GTIR's 4wd system is nothing like the GTR, its all mechanical with no smarts. GTR's use the Electronic Torque Split version of the ATTESA.

3 Re: ATTESA AWD System on 6th June 2017, 9:28 pm

typeritr

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gtir_woody wrote:GTIR's 4wd system is nothing like the GTR, its all mechanical with no smarts. GTR's use the Electronic Torque Split version of the ATTESA.

I was guessing that, as you can remove the 4wd from the GT-R by taking out a fuse, i knew that was not the case with the pulsar. That is what got me though it being called ATTESA, there is just different variants of that system. Still wondering about how the torque is split between the wheels though on the GTI-R

4 Re: ATTESA AWD System on 6th June 2017, 10:33 pm

nomad

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I think the bluebird u12 shares the same system maybe the p10 primera .... and its awd not 4wd ....


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5 Re: ATTESA AWD System on 7th June 2017, 9:55 am

gtir_woody

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6 Re: ATTESA AWD System on 7th June 2017, 9:56 am

gtir_woody

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You'll need to translate the text

7 Re: ATTESA AWD System on 7th June 2017, 12:04 pm

Cosmic73

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If you open in Google, it will offer to translate it all.

8 Re: ATTESA AWD System on 7th June 2017, 6:04 pm

GTI-R US

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Management
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In a nutshell off the top of my head (damaged though it is  Laughing )
The Attessa system works by constantly distributing drive in varying degrees across each axle by means of an lsd for each axle. The lsd contains a silicone type fluid which thickens when wheel slip is detected across that axle and applies more torque to the driven wheel until grip is regained in the slipping wheel.

In total there are 3 lsd's, the one fitted to the transfer case does a similar job to the one in gearbox (distributes across front driveshafts) and one at the rear which does exactly the same across rear shafts.
However the diff in transfer distributes drive from front to rear if slip is detected supposedly on a 50/50 ratio assuming the diff is working correctly and viscous fluid hasnt cooked itself over years of modding and abuse lol.

So in theory the car is predominantly operating as a fwd car until it starts to understeer then the viscous diff should engage and more drive applied to the rear wheels (50/50).

In reality thats rarely the case though as many viscous diffs fitted are no longer working correctly so do not distribute enough drive to the rear wheels hense why you get shed loads of understeer on the Gtir.
But in fairness many have much wider profile and largerdiameter wheels/tyres than they should be running or have sticky type rubber fitted which the viscous diff will struggle to cope with in extreme driving such as track curcuit use. Thats why many are reverting to a plated type diff.

Later Attesa systems were electronically controlled so could allow varying degrees of drive to front or rear, infac on the gtr models you can disable the system and make it rwd only if you want, so far more advanced than the system fitted to our little Pulsars


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9 Re: ATTESA AWD System on 7th June 2017, 11:21 pm

Mr B

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in general driving it 50/50 torque split much like early audi .
when slippage occurs centre viscous unit transmits more torque to axle with better grip, viscous fluid reacts in fractions of a second so torque split changes happen real quick .
So under hard acceleration you should have more drive torque to rear if all working as designed when new.
front diff is open type (modena torsen massive upgrade), centre is viscous and rear diff is viscous.
Would imagine a lot of centre diffs not reacting as fast as when new but it far superior engineering/quality than say a viscous coupling on a freelander1 lol .

10 Re: ATTESA AWD System on 8th June 2017, 9:56 am

GTI-R US

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Mr B wrote:
far superior engineering/quality than say a viscous coupling on a freelander1 lol .




Dead right with that one
has to be one of the worst diffs around, had 2 of the boogers go on my Westfield Megabusa






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11 Re: ATTESA AWD System on 8th June 2017, 10:03 am

typeritr

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Thanks for all the info on this, I know how it works now which is what I was looking for, it seems to work the way i was expecting it to with regard shifting the power around. It was probably a very advanced system back in the days they were being produced.

12 Re: ATTESA AWD System on 8th June 2017, 11:02 am

Mr B

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gtir technician
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It pretty basic really, loads of awd systems in that era (audi, mazda, subaru) using same basic principles but nissans attesa sounds fancy, only thing that clever is the quality of engineering and construction of center viscous diff and rear diff .
Why they didn't have a viscous or torsen front diff to compliment it and way better suspension design to aid putting power down to start with is beyond me .

13 Re: ATTESA AWD System on 8th June 2017, 11:44 am

typeritr

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Yeah I was just thinking that, Why after all the work did they leave the front diff open?? The inner front could spin up on hard cornering! Also designed as a rally car if your rear wheels were on ice and one front wheel was on ice you would end up spinning all 3 and the 4th (front) wheel would be rendered useless.

14 Re: ATTESA AWD System on 8th June 2017, 12:03 pm

Mr B

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gtir technician
gtir technician
I suppose as road car it forgivable to some extent as with open front it gives transmission less stress .
Given the R's understeer characteristic a lsd of some type up front would of been massive improvement to one of cars biggest driving flaws and huge marketing point back in 1990 . any rally car inc group n would easily upgraded front diff to suit needs .

15 Re: ATTESA AWD System on 18th October 2017, 8:46 am

Ryaneg6freak


GTI-R US wrote:In a nutshell off the top of my head (damaged though it is  Laughing )
The Attessa system works by constantly distributing drive in varying degrees across each axle by means of an lsd for each axle. The lsd contains a silicone type fluid which thickens when wheel slip is detected across that axle and applies more torque to the driven wheel until grip is regained in the slipping wheel.

In total there are 3 lsd's, the one fitted to the transfer case does a similar job to the one in gearbox (distributes across front driveshafts) and one at the rear which does exactly the same across rear shafts.
However the diff in transfer distributes drive from front to rear if slip is detected supposedly on a 50/50 ratio assuming the diff is working correctly and viscous fluid hasnt cooked itself over years of modding and abuse lol.

So in theory the car is predominantly operating as a fwd car until it starts to understeer then the viscous diff should engage and more drive applied to the rear wheels (50/50).

In reality thats rarely the case though as many viscous diffs fitted are no longer working correctly so do not distribute enough drive to the rear wheels hense why you get shed loads of understeer on the Gtir.
But in fairness many have much wider profile and largerdiameter wheels/tyres than they should be running or have sticky type rubber fitted which the viscous diff will struggle to cope with in extreme driving such as track curcuit use. Thats why many are reverting to a plated type diff.

Later Attesa systems were electronically controlled so could allow varying degrees of drive to front or rear, infac on the gtr models you can disable the system and make it rwd only if you want, so far more advanced than the system fitted to our little Pulsars

You are for the most part, spot on. 99% of the time it operates in FWD mostly, until some wheel slippage happens.

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