mav238

I thought the RDX, RL and MDX were the first vehicles to have an aAWD system that can direct power to a particular wheel, in particular, at the rear.

I was watching the video demonstration on the infiniti website and it seems to show that the Attesa AWD system can send more power to any one wheel if required, including the front wheels. SH-AWD can only preferentially direct power to one of the rear wheels.
If this is true, then the ATTESA system is definitely more superior to the SH-AWD system.

Am i correct with this observation?

CGTSX2004

iTrader: (1)

The ATTESA-ETS system could do it, but was always reactionary, meaning that you still needed something in the environment to trigger the action from the AWD system beyond driver input. The SH-AWD system is proactive so all it takes is the driver's input (e.g. turning of the steering wheel) to get the car calculating how much power to apply to the outside rear wheel (which incedentally is also the wheel that will have the greatest effect as it is the wheel that will have the outermost radius in a turn) and then apply it without there being any further input from the environment to cause slippage.

The real difference is proactive vs. reactive.

grooks1

I did a search on Wikipedia. Basically the Nissan/Infiniti AWD system was designed for cars are RWD and the system pushes drive to the front wheels. It states that up to 50% of the power can be directed to the front wheels. This particular system is currently used in the G35x and the FX series.

There is an updated AWD system that will transfer power to either the left or right rear wheels. They don't seem to indicate that this system is used in any U.S. manufactured vehicles. Again, most of the power is in the rear wheels which transfer power to the fronts when needed.

The acura system has more power in the front and can transfer more drive to the outside rear when needed.

mav238

Okay, I am beginning to understand better the difference...

So in snow conditions, especially in straight-line conditions, I would say it is mostly "reactionary" for any AWD system. In these conditions, the ATTESA-ETS will react by directly more power to any one wheel, depending on the road condition.
Will the SH-AWD do this too?
According to the infiniti website, power can be preferentially directed to say the front right wheel if slippage occurs there.
I don't think the SH-AWD can do that.

And to the point of proactive system in the SH-AWD, that would mean, if the roads are reasonably dry, the SH-AWD system is superior because it proactively put more torque to the outside rear wheel to cause the car to turn crisply in the corner... am I correct so far?


So in dry driving conditions, cornering in the RDX is more superior...
in snow covered conditions, the ATTESA-ETS is more superior because it can direct preferntial power to any SINGLE wheel if necessary...


any feedback on this?

CGTSX2004

iTrader: (1)

In foul weather conditions, the amount of torque the ATTESA-ETS system can transfer to any one front wheel is less than the amount of power that the SH-AWD system can transfer to the rear wheels, so your scenario about dry vs snowy conditions would not necessarily hold true. In fact, the FWD nature of SH-AWD makes it naturally better in snowy conditions due to the weight over the front wheels.

SH-AWD is a more advanced technology, but varying driving conditions and styles will really determine which one is more suitable to the individual driver. Blanket statements about one being better than the other in all conditions just is too hard to back up.

mav238

Thanks for your feedback.

So maybe the SH-AWD is more superior in terms of dynamic and performance-oriented driving, while both systems are somewhat on par in not so ideal wet/snow conditions(?).

Lrpba300

Well, not so sure you get it. Lets see if I can make it as clear as mud!
Straight line snow type conditions: Yes, you are fairly correct. Except for any variations by VSA (Infiniti's Vehicle System Assist) and VSC (Acura's Vehicle System Control) COULD make some difference in putting power to wheels that slip & wheels that grip!

You DEFEINTLY don't want to send power to wheels that are slipping!! You pull power away! This again is VSA & VSC differences between Infiniti's system & Acura's system, not SH-AWD. This doesn't regulate slipage, VSC does!

YES! This is where the Acura system is superior in that it can send .."up to 70% of the TORQUE to the rear wheels & 100% of the rear wheel power to the outside turning wheel in a corner!" This is where it is better than Infiniti's system, IMHO.

I have driven both & both seem to work well in snow/wet conditions. The big advantage in the RDX I felt was a better cornering feel b/c of prob. the SH-AWD kicking in when you go, (or slide) into/ through a corner. Just remember that the VSA & VSC systems play a larger part in that senerio. As someone already said, In the G35x, the system is built around a RWD type system w/ 50% of the torque going to the front & rear when needed. The RDX is built around a FWD/ AWD system, where up to 70% of the torque goes to the rear w/ the ability to put up to 100% of that rear torque to the outside turning wheel!
There! How's that? I hope I got it all right & isn't too confussing!

Lrpba300

Woops! It's VSA is Acura's system name & VSC is the Infiniti's system name!

TSX69

Maybe I am dreaming this up but I thought I read once the SH-AWD made its 1st appearance in a Prelude? Granted it was a simpler version but still the basis of what is out now ....

CGTSX2004

iTrader: (1)

The Prelude SH had the active torque transferring characteristics in its differential, but it did not have AWD. The SH diff on the Prelude SH was functionally the same design as the rear diff on the RL and RDX.