Confusing AWD with TCS
CXRabbit said:
You do realize that the CX-7 is not FULL TIME all-wheel drive. AWD only kicks in when the system detects a traction different between the front and rear tires, due to the front wheels slightly slipping.
I think there is some confusion with regard to the AWD system not being full time... the TCS (traction control system) is the part that only engages when a loss of traction is detected, and TCS is a braking process that operates within the anti-lock system. TCS prevents a drive wheel from endlessly slipping and spinning free from a loss of "grip", such as a wheel that begins slipping on ice, because THAT is what you NEED to regain traction.
AWD is just what is says it is - all wheel drive, and AWD all by itself, does not have a meaningful advantage on ice because these systems need to detect resistance to work optimally. The old 4x4's were basically dual posi-traction, meaning that only ONE front and ONE rear were turning at any given time, and it would be the one with the MOST resistance.
Modern AWD systems are "dynamic", and CONSTANTLY distributing and redistributing some of the drive power to all four wheels according to the system's logic. These systems can sense the relative resistance or "grip" of each wheel, and direct either more or less of the torque based on that. You may not have all 4 wheels driving at the same time, but they all get equal time, with most often, a bias to favor the front wheels. Once lifted off the ground, AWD ceases to properly function because it can not detect any resistance.
It seems to me that the CX-7 can allocate up to 50% of available drive power to the rear wheels. Any one with an AWD model does indeed have all for wheels pulling rubber over the road. One of the big selling points on the RDX is that it has a system that can direct up to 100% to one side for optimal handling & traction while cornering. Some may argue the practical benefit or need for such a dramatic power allocation, and I would be one of them.
The best way to think of these systems may be to understand that ABS and TCS work through the braking system by monitoring & comparing relative wheel ROTATION. AWD delivers torque through the drive-train by monitoring & comparing relative wheel RESISTANCE. And that my friends is what make a vehicle sure-footed!
Over the past 30+ years, I have driven NOTHING but 4x4 and AWD - 1985 Dodge Ramcharger, 1992 Eagle Talon Turbo AWD, 1993 Ford Bronco, and 4 different Subaru Legacy GTs, and now a CX-7. If someone knows that I'm out-to-lunch on this, please make your case, but I think some are confusing the AWD for the TCS.
Does AWD make a difference over FWD? I wouldn't drive anything without AWD, and I haven't.