Front/rear torque split

[sy300]

The Stagea runs full ATTESSA (like an R33 GTR, but with different calibration), so there is no one torque split, it is infinitely variable from 100% rear drive to 50/50.  The ATTESSA controller determines the split based on the inputs, speed, engine rpm, gear, throttle position and most importantly G forces.

It should not be compared to the simplistic 4wd split that we see in front wheel drive supplied 4wd's.   Some of which use the ABS sensors to detect wheel slippage, which is far too late in the equation.  Plus they can never go more than 50% rear drive, which limits  their handling envelope.

Does it tale into account wheel spin? How does it cope with different surfaces like gravel or snow/ice, which have less grip, and therefore you would have to split the power earlier to avoid losing grip.

What I'm trying to say is: If it takes input from the sensors you mentioned above, and then pre-empts any wheel spin, how does it know what surface you are driving on? The surface would make a difference because you begin to slid or loose traction sooner on gravel, etc than on the road.

It certainly seems like a great system, all I can get from it is a couple of 'chirps' when taking off quickly while turning. I tried it around a sharp, low speed corner in the wet the other day, it just seems to pull into line when you plant your foot. It's quite hard to get used to compared to my previous 300ZX, which was always happy to go sideways in the wet even with 255's on the back.

[Sydneykid]

Does it tale into account wheel spin? How does it cope with different surfaces like gravel or snow/ice, which have less grip, and therefore you would have to split the power earlier to avoid losing grip.

What I'm trying to say is: If it takes input from the sensors you mentioned above, and then pre-empts any wheel spin, how does it know what surface you are driving on? The surface would make a difference because you begin to slid or loose traction sooner on gravel, etc than on the road.

It certainly seems like a great system, all I can get from it is a couple of 'chirps' when taking off quickly while turning. I tried it around a sharp, low speed corner in the wet the other day, it just seems to pull into line when you plant your foot. It's quite hard to get used to compared to my previous 300ZX, which was always happy to go sideways in the wet even with 255's on the back.

The surface affects the G forces, obviously slippery or loose surfaces generate lower G forces for both cornering and accelleration. The G force sensors measure this and tell the ATTESSA controller.

[sy300]

The surface affects the G forces, obviously slippery or loose surfaces generate lower G forces for both cornering and accelleration.  The G force sensors measure this and tell the ATTESSA controller.

I think I'm missing something.

If the controller waits until, say, 0.5g acceleration before transfering torque, which is fine on the road, but on gravel you would already be sliding or spinning the wheels.

What am I missing? It is a reatively simple system, but I can't get my head around this particular thing.

Thanks for taking the time to answer my questions.

[Sydneykid]

I think I'm missing something.

If the controller waits until, say, 0.5g acceleration before transfering torque, which is fine on the road, but on gravel you would already be sliding or spinning the wheels.

What am I missing? It is a reatively simple system, but I can't get my head around this particular thing.

Thanks for taking the time to answer my questions.

I though I covered this, with this post;

3. Yep it doesn't wait for wheelspin, the G Force sensor tells it there is less chassis acceleration than engine (rpm) acceleration and/or speedo acceleration.

The engine is accelerating (rpm increasing) but the G Forces don't correspond to that amount of engine accelleration (in that gear). Fast engine acceleration and low chassis acceleration = wheelspin.

Hope that made sense:cheers:

PS; with a 2 axis G force meter I could draw a map of wherever you went, that's how a data logger works in a race car. Acceleration over time = distance, so not only do I know how fast you have travelled, but I also know what direction you travelled in and for how long, hence I know how far you went.

[sy300]

I though I covered this, with this post;

 

The engine is accelerating (rpm increasing) but the G Forces don't correspond to that amount of engine accelleration (in that gear).  Fast engine acceleration and low chassis acceleration = wheelspin.

Hope that made sense:cheers:

PS; with a 2 axis G force meter I could draw a map of wherever you went, that's how a data logger works in a race car.  Acceleration over time = distance, so not only do I know how fast you have travelled, but I also know what direction you travelled in and for how long, hence I know how far you went.

Ahhh, that's what I was missing.

Now I understand. Thanks for that.

Sorry if it felt like hitting your head on a wall, but sometimes it can be hard to explain things when only using text.

[r31gts]

Hey guys, I just fixed a 4wd issue in my stagea and got a little info on the system used in these cars. First thing i want to meantion is that nissan told me that if u leave the ATTESSA pump on for more than 30 seconds you can damage the internal parts of the 4wd system. also the pump does switch on with the ignition but onlY for a few seconds, and only comes on every now and then depending on the required tourque split.

Rob

[Sydneykid]

Hey guys, I just fixed a 4wd issue in my stagea and got a little info on the system used in these cars. First thing i want to meantion is that nissan told me that if u leave the ATTESSA pump on for more than 30 seconds you can damage the internal parts of the 4wd system. also the pump does switch on with the ignition but onlY for a few seconds, and only comes on every now and then depending on the required tourque split.  

Rob

Hi Rob, on the race cars the ATTESSA pump runs most of the time. After all it's just a hydraulic pump, and the hydraulic pressure it produces is used to load the clutch plates via solenoids. When there is no need for hydraulic pressure, the solenoids bypass the flow and if that time is long enough, the pump eventually turns off.

On the later systems (R33/34) the solenoids hold a residual amount of pressure (even without the pump running). This means quicker response when 4wd is needed (ie; no delay while the pump builds up pressure). This is one of the reasons why R34 GTR's don't have the initial power oversteer that an R32GTR has.

I am not sure what they meant by "leave the pump on" :confused: The reality is the bypass solenoid (controlled by the ECU) will prevent any load on the clutches if the pump is running when it is not needed. The pump has almost zero load, hydraulic fluid simply goes around and around, just like the fuel and the fuel pump does when the engine is idling. If that went on for a few hours then the hydraulic fluid would get pretty hot, but that's about it.

All good info, but tell us what was "the 4wd issue in my stagea" that you "just fixed"? And how did you fix it?

[StageZilla]

Hi Rob, on the race cars the ATTESSA pump runs most of the time.  After all it's just a hydraulic pump, and the hydraulic pressure it produces is used to load the clutch plates via solenoids. When there is no need for hydraulic pressure, the solenoids bypass the flow and if that time is long enough, the pump eventually turns off.

On the later systems (R33/34) the solenoids hold a residual amount of pressure (even without the pump running).  This means quicker response when 4wd is needed (ie; no delay while the pump builds up pressure).  This is one of the reasons why R34 GTR's don't have the initial power oversteer that an R32GTR has.

I am not sure what they meant by "leave the pump on" :confused: The reality is the bypass solenoid (controlled by the ECU) will prevent any load on the clutches if the pump is running when it is not needed.  The pump has almost zero load, hydraulic fluid simply goes around and around, just like the fuel and the fuel pump does when the engine is idling.  If that went on for a few hours then the hydraulic fluid would get pretty hot, but that's about it.

All good info, but tell us what was "the 4wd issue in my stagea" that you "just fixed"?  And how did you fix it?

awesome info there sk cheers for that, helping my lack of understanding of this bloody attessa system :thankyou:

still cant work out y my attessa fluid is virtually boiling and erupting out of the gearstick hole which makes me think the pump is wired up to run 24/7 :hellpisd:

cheers

Brad

[Tangles]

Questions:

Stagea is in an auto electricians place, need urgent help regarding the 4wd system.

1. Where is the attessa unit? rear right hand area around the wheel well?

2. Where is the attessa pump? if the pump is faulty, would this then start blowing abs fuses in the engine bay?

3. Anyone got a wiring diagram of the 4wd system, or cvan point me in the right direction.

Im not sure if the people who installed the stereo, and the electricians now who are going over the car, know where these things are.

Im stressed out a bit - any help would be appreciated.

Brendan

[AlexCim]

I can power oversteer quite easy in my car in the wet, not in the dry at all

some more power will fix it.

I find it really easy to control sideways, i can get some pretty big angles too...

but, this does involve a lot of first gear and some rev limiter sometimes. I cant hold a slide longer then a few seconds, which is about all of first + some limiter.