It looks like I can provide a little bit of evidence to support the car engaging AWD in corners and from a launch.

Wikipedia says: "To control the ATTESA E-TS system, there is a 16-bit computer that monitors the cars movements 10 times per second to sense traction loss by measuring the speed of each wheel via the ABS sensors. Also a three-axis G-Sensor mounted underneath the center console feeds lateral and longitudinal inputs into a computer, which controls both the ATTESA-ETS 4WD system and the ABS system. The computer can then direct up to 50% of the power to the front wheels. When slip is detected on one of the rear wheels (a rear wheel turn 5% or more than the front wheels), the system directs torque to the front wheels which run a non-limited slip differential. Rather than locking the AWD in all the time or having a system that is "all or nothing", the ATTESA E-TS system can apportion different torque ratios to the front wheels as it sees fit. This provides the driver with an AWD vehicle that performs like a rear wheel drive vehicle in perfect conditions and can recover control when conditions aren't as perfect."

So it appears that the car uses a gyroscope to sense where the power needs to be sent. If the G sensor determines that there is heavy acceleration or a sharp turn, it will react to ensure grip is maximized. Also, the system can distribute torque to act as an electronic limited slip differential.

 

I think your interpretation is correct. Just keep in mind that every AWD system will either act like a limited slip or a locked differential. An open differential AWD system would pretty much do nothing. The real key is (as you allude) the ability to dynamically vary torque front to back. This will be an advantage pulling out of the hole or in low traction conditions.

I am not sure that this system will actually help much in corners however. Because the differentials front and rear are both open; your torque application is still limited to the minimum torque that can be applied to one of the rear wheels, times two, plus the minimum torque that can be applied to one of the front wheels, times two. The RWD car can apply the minimum torque that can be applied to the rear wheel times two, plus some coefficient (with a viscous LSD, let's call it 0.2-0.3) times the torque that can be applied to the other wheel. In a hard cornering situation where wheels are loaded in a laterally asymmetric fashion, the AWD system may lose much of it's headroom. Obviously, if max torque is equal laterally across the car, the AWD system delivers more grip (i.e. straight line acceleration over constant terrain).

Keep in mind that the AWD system adds some weight and rotational mass (I'll ignore center of gravity issues since cars can be lowered) and it's hard to pick a clear winner. If you held my feet to the fire, my intuition would be that off the line performance and poor traction situations (for instance slick roads) would favor AWD while the lighter weight of RWD coupled with the limited slip differential in the rear would give it an advantage when cornering on dry road.

Anyway, just my 2 cents based on some assumptions. The only way to know for sure would to do side by side testing of both cars, both with the same transmission, with the same driver. Even then, to be fair the AWD car should be lowered (also AWD doesn't get the same anti-roll bar in the rear that the S RWD does).

 

I can't imagine Infiniti using a smaller sway bar in order to "cripple" the awd model in an effort to sell more RWD models. I figured they needed a weaker rear sway in order to prevent oversteer because of how the awd differs.

 

I'm not suggesting that they tried to cripple the AWD car. I would imagine that it is because:

1) The ride height of AWD is higher, stiffer anti-roll bars can make wheels want to lift and perhaps the higher center of gravity exacerbated this.

2) AWD is targeted towards conditions where road surfaces may not be so good (northern states for instance). Stiffer anti-roll bars add harshness, perhaps they were trying to mitigate this.

I don't think preventing oversteer was their goal however, AWD generally has less oversteer, not more. A stiffer rear anti-roll bar will be likely to increase oversteer. If anything, you might expect the AWD car to have a stiffer bar as it will be more prone to understeer than the RWD model.

 

Even where I live in Northern NJ, AWD is not needed for nearly 9 months of the year anyway. Maybe Dec to Feb, March to Nov you are fine. The rear drive model does better in the snow then I thought it would.

 

The RWD coupe is around 200 lbs lighter than the AWD coupe, I believe 0-60mph the RWD is 3/10's faster? Depends on the magazine tester. The RWD should feel just as secure as the AWD, pending tires, road condition and driver. AWD will just be better if you have to take off hard from a stop in the rain. Otherwise highway speeds, it comes down to the tires.

 

There's absolutely no need to get AWD anywhere south of Maryland. Even in MD, you will use AWD all of about 2 or 3 times a year. Those are the times I leave my car in garage and use a different car. Totally worth it as I don't have to deal with crappy all season or snow tires and just have summer tires on all year around.

Also Infiniti AWD system is not as good as the one in GTR, it actually makes your car somewhat slower and doesn't help with launching. It's purely a safety system for when the rear wheels start slipping.