Only concerning the 50/50 lockup:

The snow mode button can be likened to part-time 4 wheel drive - part time 4 wheel drive locks the wheels together.. I think the right/left sides, so the problem occurs when you turn the vehicle lets say to the right.. (the tires will go different distances, thus travel different speeds)
The front left tire should turn the fastest, the front right should turn the slowest and the rears will be somewhere in between.. When the 4 wheel drive is locked in, the tires will turn at the same speeds (at least left side/right side), on snow there will be slippage and it will not be detrimental to the drive train, HOWEVER, on dry pavement since the tires will turn at the same speeds, even though they should not be, there will not be very much slippage between the tires and road, so the drive train takes the bulk of the stress..

Regular mode can be likened to full-time 4 wheel drive. - full-time 4 wheel drive only locks up the non-primary axels as needed, allowing slippage when necessary, even on dry pavement, so the drive train doesnt have to deal with the stress.

 

[QUOTE=geew1z;4806032] The front left tire should turn the fastest, the front right should turn the slowest and the rears will be somewhere in between.. When the 4 wheel drive is locked in, the tires will turn at the same speeds (at least left side/right side), on snow there will be slippage and it will not be detrimental to the drive train, HOWEVER, on dry pavement since the tires will turn at the same speeds, even though they should not be, there will not be very much slippage between the tires and road, so the drive train takes the bulk of the stress..[/quite]

Bingo. I beleive if you were to add up the distances traveled through a turn of each wheel, you'd find the front wheels travel slightly further through the turn than the rears



I think you mean part-time 4WD here

 

I believe what you meant is that when the 4 wheel drive is locked in, the front/rear tires will be forced to rotate at the same speed.

The differentials at the front and rear axles are not lockable differentials (and they're not limited-slip, either, for that matter), and therefore the left side/right side wheels are never restricted to the same rotational speed.

When snow mode is engaged, the clutch pack in the transfer case is locked up, and torque is transmitted to the front driveshaft, thereby locking together the rotation of the front output shaft (going to the front driveshaft) with the rear output shaft (going to the rear driveshaft).

The clutch pack consists of several friction plates on the input shaft (driven by a chain) interleaved with several friction plates connected to the front output shaft. In the ATTESSA E-TS, an electric pump in the rear differential sends pressurized tranny fluid (0-288psi) to the clutch pack. The fluid progressively presses the friction plates together (hence a "wet" clutch pack). 0psi of pressure results in no contact; our car is RWD. 288psi and all the friction plates our pressed together, making our car is 50:50.

So any disparity in front/rear rotation would, in essense, cause wear on the weakest link between this clutch pack and the tires. It is my guess that the wet clutch pack is this weakest link, rather than the differentials which employ meshed gears rather than friction. I don't know how substantial 288psi of "clamping force" nor what material the friction disks of the clutch pack are made of. But I doubt that it is very substantial, since its a small electric pump pressurizing the fluid. I'd have to conclude that it's in this part of the system that the Nissan engineers would have to design for some tolerance, and be able to deal with some disparity in the rotational differences

 

No.. the wording is confusing, but part-time 4 wheel drive is locked in..and is usually only supposd to be used up to 25mph.. They call it part-time because it shouldnt be used all the time.. Full-time is like awd in that the power is diverted as needed somehow.. I remember being really confused about that wording though..

 

hahah burnout in the x... that's humour

 

I remove the front driveshaft in summers for burnouts and sideways fun, and re-install it in the winters.

Ok, I don't actually do that. But itechnically its possible.

 

Hahahahah

The email I got cut off the quote- I didn't see that you were joking till I came to the thread

 

From what i read, this is what they did to the gtr used in fast and the furious in order to get it to react even slightly in the way they wanted for a movie..

 

You are right. The wording of it confused me as well.





I kinda wonder how Subaru or Audi manages their AWD system to offer a 50:50 split all the time? I was reading the brouchure on my father's '10 outback and they offer THREE different AWD transfer case setups depending on if you get the Manual trans, Auto trans or the CVT. I wonder how they allow for slip to compensate for the differences in wheel speed through a tight turn with their setups

 

I read that they used a RWD model from the start.


Kinda like how the 10 second Eclipse GSX from the first movie was just an RS that barely ran 14's

 

Sounds reasonable enough. Since ATTESA E-TS sends torque to the front driveshaft is via a wet multi-plate clutch pack and not a viscous coupling, removing that driveshaft it shouldn't have any negative effect on the mechanism.

Here's an interesting diagram showing how the ATTESA E-TS ECU responds to the various driving conditions which can be encountered, detected with 100 inputs per second from the ABS sensors and the 3-axis G-sensor under the center console.

 

apparently the Torsen center diff in those cars allows the slippage necessary.. http://en.wikipedia.org/wiki/Torsen

Also it appears that the Audi's anyway, have the ability to increase power to rear/front if needed too, just is typically 50/50. I actually haven't driven an audi hard, wonder how that feels with that type of configuration

 

yeah, most of the cars they used were actually crap... huh i just read about that gtr last month, but if there was a RWD option, then obviously that makes more sense

 

I still believe that turning has nothing to do with it, since any differences between the left & right wheels are accounted for by the axle's differential, and has nothing to do with the power distribution front to rear.

AWD systems are all different, but all that's necessary to keep it locked 50:50 is to allow for some tolerance of rotational differences front to rear.

Subaru's Symmetrical All-Wheel drive layout is totally different from ATTESSA. In a Subaru, there is no front driveshaft. The front half-shafts come directly out of the transfer case, where there is a clutch mechanism that distributes the power left to right, and front to back to the rear driveshaft. VW's latest Quattro system (in the sedans) uses a Haldex limited slip coupling with a limited slip differential to vary power distribution.

 

True, but if you measure each wheel's arc radius through a turn, i beleive the rear wheels travel smaller arcs that the front two wheels.

The outer front wheel travels the biggest arc, while the inner rear wheel travels the smallest arc. The other two wheels turn arcs between them, but not sure if they are proportional. The tighter the turn, the bigger the other differences.

I'd look up info to support this if i was home, but limited here at work.


Very good discussion btw...