Re: R AWD vs. other Volvo AWD (VolvoFaRmeR)
| Quote, originally posted by VolvoFaRmeR » |
| Does anyone REALLY know how the R AWD decides when and how much power to shift to the rear? |
I would
strongly like this thread not to die.
Unfortunately I don't think anyone here has the answers to your very important questions. All you can find is incomplete opinions, like the one you are about to read.
The way I understand it, the hardware in the R is exactly the same as in other AWD Volvos. (This is technically not true since we have seen that the angle gear and sleave were uprated, but to the computers managing the show, the underlying hardware looks exactly the same).
The basic premise is as you described: the car has a gazillion sensors, and based on those inputs, a computer decides
when and
how much power to send to the rear wheels.
This is a dynamic calculation (that means continuously updated as you drive, not like an on/off locking diff)
It is very unlikely that Haldex/Volvo will ever release the exact control algorithm.
Some remarks I have read:
-speed triggers Haldex engage/disengage events (some say at 30 mph, and 60mph there are break points, but that is speculation at best)
-when cornering in the R model, Haldex engages to counter understeer
-the speed of coupling under slippery conditions is controlled by the front to back speed differential (aka if you want to collar gear to survive, don't floor it as the fronts spin)
Unfortunately, these are all "backchannel" and "I heard that" statements.
How does a S60R compare to a AWD S60?
I THINK what changes between models is the programming of the computers. Further, the programs could be identical or very similar, just use different
parameters. For instance, cap the maximum torque that is transferred to the rear wheels, or limit the speed of coupling of the Haldex clutch to provide a smoother ride and drivetrain longevity
How do I know this is true?
I don't, and that saddens me.
All this has been gathered from reading the archives of this forum and discussions from friendly Haldex engineers. You can do it yourself if you feel so inclined (haldex.com). What is
really hard, is to get someone at Volvo to talk to you.
Like the OP said, does anyone REALLY know this stuff? we would love to be enlightened http://********************/smile/emthup.gif
