AWD system?

[Jay-Rock]

i was wondering how the AWD systems work on the awd cars? my mom has a new car, that is front weel drive untill the front weels slip, then the backs kick in. are these cars alwayz in awd? or is it something liek htat? thanx

 

[NDgsx]

50/50 power split until one end looses traction.

 

[RocketDSM]

I have seen systems that work like your describing, but mainly in Japan (I was stationed there with the Navy). Those systems are more for traction control than AWD. They use the AWD nomenclature due to the fact that it is not 4WD and AWD makes it sound better than "Traction Control Rear Drive System". As said, ours us a constant 50/50 until something slips. The advantage of the other type of system is that you don't have driveline loss for the whole AWD system until you lock up the center diff/transfer case. This gives you better jump up to limits of traction, with only a small loss when the system shifts over to AWD. It's not a bad setup, but has MANY querks. As I said, JDM cars of various types have been using it for years. Performance drivers who were not well expirenced on those cars found it unsettling as the car would suddenly change disposition in the middle of a corner as the front tires slip and it shifts to the rear. Just takes some getting used to really, not a bad thing overall.

 

[AW4G63]

I love a little driftin!

 

[GRNDSM]

>Those systems are more for traction control than AWD.

Actually, a lot of US market vehicles have this system in now days (CVR, Volvos, Audi TT, and a few others).

>The advantage of the other type of system is that you don't have driveline loss
>for the whole AWD system until you lock up the center diff/transfer case.

You know, that is what they claim. But I wonder just how much of this true? Their rear axle, rear diff and the driveshaft are still spinning 100% of the time, they are just not transmitting the torque. So they still have most of the parasitic driveline losses of a true AWD.

Personally, I think that they do this for two reasons:

1. To use this and an advertising gimmick and make people think that their car is just economical as FWD car most of the time (very important for PC segment of the population).
2. To “dumb down” the car so that an average diver will be less likely to spin it. For example, DSMs were intentionally designed to understeer like crazy to make them less likely to overseer (something that an average driver would tend to do with RWD or 50/50 AWD car).

Neither reason seems good to me, but they are perfectly fine for “mom’s new car” .