Quote:
Originally Posted by SlingShot
The amount of misinformation about EPS in this thread is unbelievable. In a nutshell all they did was to replace the belt driven pump with an electric pump. All the rest of the mechanics is still the same. If the electric pump was to fail, it would be no different than having a power steering belt break. Hard as hell to steer without a manual gear in it, but still very doable.
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I dont *think* this is quite the case...from my impression, it is a 'belt driven' system, but no hydraulics...theres a brushless motor parallel to the rack, the one end of the rack has a ballscrew thread cut into it, the belt drives the hollow ballnut (x and z axes on my CNC bridgeport works same way), so the motor torque effectively moves the rack. so if the motor turns(driver input or not) the steering rack moves. ZL1 uses just one of many proven/similar systems out there, but to me, ever since seeing Fords 'park assist' feature, the whole EPS thing in my worry wart way of thinking, kinda makes me glad mines still hydraulic...
although when our ford/newholland tractor broke a line, my son almost hit a tree...'supersteer' dont work AT ALL if the oils gone
I'm sure theres a ton of failsafe/fault detection stuff in there on all this EPS stuff, CNC servos have them too to prevent a 'situation', but on CNC machine applications I'm used to seeing, if a brushless motor loses commutation channels, it will try to jump slightly just before it faults...
my apprehension of these is *what if* the motor jumps ever so slightly, then safetys trip it out, you mighta just done a lanechange and then didnt have assist while correcting with one hand loosely on the wheel...
not saying this is what happened with Cam's car, but this is exactly why i dont like the EPAS as most are done...if it was simply electrically powerred hydraulic pump I would have no apprehension at all of it...I still think this would be the best system, but with both electrc and hydraulics, it wont be as cheap as one or the other...I just think the hydraulic is a lot more failsafe. I tore apart a couple boxes/racks, the torsion bar valving is pretty robust, if the bar breaks the system still works, just no road feel, the valves are pretty clogproof esp on the old recirc ball boxes, racks, meh...
edit: found TRW's page (they make the ZL1 box, and many other makes use them too) if interested:
http://www.trw.com/sub_system/electr...wered_steering