How does the '11 AWD system REALLY work?
07-07-2012, 12:12 AM
#31
Registered User
I don't think it does at least not in the 2011s. There is no documentation to support it. I drove a jeep that had a locking diff and know what binding is. My g does not bind when the snow button is engaged under 12 mph.
07-07-2012, 12:23 AM
#32
07-09-2012, 11:56 AM
#36
Here's a video of a G37x on a dyno. Note that all 4 wheels are powered.
Last edited by DocJohn; 07-09-2012 at 12:02 PM.
07-09-2012, 02:30 PM
#37
Administrator
I feel like the same things are being said over and over again
08-23-2012, 05:12 PM
#39
Why? The system we have is the best of all worlds compared to every other AWD system out there (and I have owned and driven plenty of them).
You always want to have RWD as a base (if you care about sporty driving that is) -- check.
You want to be able to have instantaneous and smooth transition to AWD when needed, with no torque steer -- check.
You want to be able to lock it into 50/50 for deep snow/mud/gravel/etc. -- check.
You want two-wheel drive for better fuel economy for the 95% of the time you don't need the extra traction -- check.
You want AWD for launch (which our system has, based on speed and throttle position, it always launches from a rest in AWD mode and then quickly reverts to RWD when it figures out you are not slipping) -- check.
What's left that the Nissan system is not superior for?
Having a permanent 60/40 or 50/50 split has only one advantage--predictability. This is rendered irrelevant in the world of electronic traction control and other nannies. It is also a double-edged sword: it is predictable that you will understeer under heavy throtlle while turning. I prefer the balance of RWD (that all sports cars use), but the "nanny" of AWD ready to jump in in a split second if I screw-up or some unexpected loose surface or road problem suddenly appears.
I would love for somone to list a scenario where the ATTESA system is inferior to mechanical AWD (Audi larger models and Subaru manual transmission), the traction controlled open diff systems like BMW and M-B or Haldex (or Haldex-like) systems on FWD cars (pretty much everything else out there).
You always want to have RWD as a base (if you care about sporty driving that is) -- check.
You want to be able to have instantaneous and smooth transition to AWD when needed, with no torque steer -- check.
You want to be able to lock it into 50/50 for deep snow/mud/gravel/etc. -- check.
You want two-wheel drive for better fuel economy for the 95% of the time you don't need the extra traction -- check.
You want AWD for launch (which our system has, based on speed and throttle position, it always launches from a rest in AWD mode and then quickly reverts to RWD when it figures out you are not slipping) -- check.
What's left that the Nissan system is not superior for?
Having a permanent 60/40 or 50/50 split has only one advantage--predictability. This is rendered irrelevant in the world of electronic traction control and other nannies. It is also a double-edged sword: it is predictable that you will understeer under heavy throtlle while turning. I prefer the balance of RWD (that all sports cars use), but the "nanny" of AWD ready to jump in in a split second if I screw-up or some unexpected loose surface or road problem suddenly appears.
I would love for somone to list a scenario where the ATTESA system is inferior to mechanical AWD (Audi larger models and Subaru manual transmission), the traction controlled open diff systems like BMW and M-B or Haldex (or Haldex-like) systems on FWD cars (pretty much everything else out there).
I just tested this about 5 times. Pretty slanted driveway upwards. Asphalt apron extending down, then gravel. Put the fronts on the apron, rears on the gravel. About half-throttle from a dead stop, the rears kicked gravel.
I don't know if they just gained traction or if the fronts kicked in. Either way it does not seem to support the AWD is in effect from a start @ a dead stop. All car systems enabled, traction control, etc.
Can someone enlighten me on this?
08-23-2012, 06:50 PM
#40
Registered User
The G does not "lock" anything. There are no limited slip differentials in the X- just two open diffs. If the rears slip, traction control kicks in and activates wet clutches in the front open diff to start the front wheels.
I don't believe there is anything close to a "50:50" locking scenario..it is not Torsen and has no mechanical way of achieving this. I know from experience the fronts can kick in fairly quick, but my driveway is loose gravel and often the rears spin for a couple of seconds before the front does anything.
There is also no real torque vectoring - it mentions doing this with EBD (electronic braking) in that video but that is just braking one wheel with more slip to get the other to spin faster, an artificial/cheap way of doing things.
So NO, in the snow, it's not as good as Quattro or Subaru's permanent split that have real locking differentials. For performance, it is good (better than Haldex, which is FWD-based), and also gets better gas mileage over permanent systems. But it is essentially equivalent to MB's 4matic or BMW's Xdrive.
The GT-R has a nicer version of the AWD system (Attesa PRO) that utilizes a real LSD at the rear that can also do real torque vectoring, as well as a seperate driveshaft from the rear powering the front wheels.
I don't believe there is anything close to a "50:50" locking scenario..it is not Torsen and has no mechanical way of achieving this. I know from experience the fronts can kick in fairly quick, but my driveway is loose gravel and often the rears spin for a couple of seconds before the front does anything.
There is also no real torque vectoring - it mentions doing this with EBD (electronic braking) in that video but that is just braking one wheel with more slip to get the other to spin faster, an artificial/cheap way of doing things.
So NO, in the snow, it's not as good as Quattro or Subaru's permanent split that have real locking differentials. For performance, it is good (better than Haldex, which is FWD-based), and also gets better gas mileage over permanent systems. But it is essentially equivalent to MB's 4matic or BMW's Xdrive.
The GT-R has a nicer version of the AWD system (Attesa PRO) that utilizes a real LSD at the rear that can also do real torque vectoring, as well as a seperate driveshaft from the rear powering the front wheels.
Last edited by jepva; 08-23-2012 at 06:59 PM.
08-23-2012, 09:32 PM
#41
The G does not "lock" anything. There are no limited slip differentials in the X- just two open diffs. If the rears slip, traction control kicks in and activates wet clutches in the front open diff to start the front wheels.
I don't believe there is anything close to a "50:50" locking scenario..it is not Torsen and has no mechanical way of achieving this. I know from experience the fronts can kick in fairly quick, but my driveway is loose gravel and often the rears spin for a couple of seconds before the front does anything.
There is also no real torque vectoring - it mentions doing this with EBD (electronic braking) in that video but that is just braking one wheel with more slip to get the other to spin faster, an artificial/cheap way of doing things.
So NO, in the snow, it's not as good as Quattro or Subaru's permanent split that have real locking differentials. For performance, it is good (better than Haldex, which is FWD-based), and also gets better gas mileage over permanent systems. But it is essentially equivalent to MB's 4matic or BMW's Xdrive.
The GT-R has a nicer version of the AWD system (Attesa PRO) that utilizes a real LSD at the rear that can also do real torque vectoring, as well as a seperate driveshaft from the rear powering the front wheels.
I don't believe there is anything close to a "50:50" locking scenario..it is not Torsen and has no mechanical way of achieving this. I know from experience the fronts can kick in fairly quick, but my driveway is loose gravel and often the rears spin for a couple of seconds before the front does anything.
There is also no real torque vectoring - it mentions doing this with EBD (electronic braking) in that video but that is just braking one wheel with more slip to get the other to spin faster, an artificial/cheap way of doing things.
So NO, in the snow, it's not as good as Quattro or Subaru's permanent split that have real locking differentials. For performance, it is good (better than Haldex, which is FWD-based), and also gets better gas mileage over permanent systems. But it is essentially equivalent to MB's 4matic or BMW's Xdrive.
The GT-R has a nicer version of the AWD system (Attesa PRO) that utilizes a real LSD at the rear that can also do real torque vectoring, as well as a seperate driveshaft from the rear powering the front wheels.
08-23-2012, 09:39 PM
#42
Registered User
Ok? The G has no center differential fyi. Yes, three lsds is optimal ( like the evo) but not necessary.
08-23-2012, 10:12 PM
#43
Snow mode in G.
1) Starts the car off in second gear to lower torque output
2) Increases sensitivity of the VDC so it intervenes sooner to stop wheel-spin.
3) Locks the torque split 50/50 up to a certain speed, after that it reverts to the normal torque split programming.
4) Softens throttle response.
1) Starts the car off in second gear to lower torque output
2) Increases sensitivity of the VDC so it intervenes sooner to stop wheel-spin.
3) Locks the torque split 50/50 up to a certain speed, after that it reverts to the normal torque split programming.
4) Softens throttle response.
08-23-2012, 10:14 PM
#44
08-24-2012, 08:24 AM
#45
Registered User
It doesn't lock anything though - there is no mechanical limited slip involved at all. Electronics send a signal to a pump that pressurizes wet clutches in the front transaxle/differential. I think it may have the ability to send UP TO 50% to the front IF maximum conditions are met, but this is realistically not going to happen much. The rear wheels would probably need to have zero traction. If you pulled the ABS or VDC fuse, the G would be RWD only.