Quote:
Originally Posted by drob23
Well thanks for your approval and the backhanded complement.
Go read this
Simpler is better if the purpose is served, since you are such an expert on control systems, what do you recommend auto makers do? Do you realize how complex the interconnections are, and the fault mechanisms built into CAN? The cost constraints for a mass produced/low margin product are not trivial.
You have been putting *a lot* of words into my mouth. The torsen is NOT feed forward, what are you talking about? I pointed out that a torsen/mechanical center diff is better at minimizing wheel slip as it does not require any estimation, it just does it. I never said it was better in corners or anything of that nature. Previous versions of Audi vehicles have suffered from understeer horribly. First change was to increase nominal gearing to 40-60, now they have included active rear diff. More torque will naturally go to the rear wheels when accelerating because the vehicle will pitch backwards and there will be more available tractive force. Electronic center diffs are more useful for rally racing, where wheels can go off the ground.
Huh, wtf does this have to do with feed forward design? The GT-R is built from the ground up to be a race car and the control system is necessarily very advanced and highly tuned. This is not the same system as xdrive which comes on a 320ix 32k car. You pay *a lot* of money to maintain this cars drivetrain. |
At the end of the day, feel free to believe whatever you want. Our discussion has gone well beyond the scope of whether to opt for xDrive or not. The trend of AWD system design definitely lean towards active differential and why not? On an ESP equipped vehicle, you have all the sensors in place already. Computing power is cheap these days. Sure R&D cost money but that's how I get paid.
Given the current state of affair, more performance can be extracted with an active differential whether it is placed at the front, center, or rear. Which is why I mentioned GT-R. It simply finds more grip than your beloved "feed forward control" passive design. Shame that earlier GTR had transmission made out of glass and even today a switch on the dash dedicated to void your warranty.
A notable exception to this trend by the way is the 2014 AMG E63 4matic. Which is as KISS as it gets. It will be interesting to see how much benefit a simple AWD system brings to that beast, and how BMW reacts for that matter. I certainly hope that BMW do more than just try to set a new drift record with the M5.
Oh and with the GT-R, cost of differential fluid is not that bad, it's the transmission fluid that kills you. The late model Lancer Evo, incidentally the topic focus of the article you linked to, require scheduled diff fluid change just the same, though perhaps the cost is not as outrageous.