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2660 messages, Last post on Sep 30, 2009 at 9:38 AM
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Your Community Leaders are ateixeira and rsholland.
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Replying to: paisan (Feb 18, 2007 11:22 am) http://www.acura.com/index.aspx?initPath=RDX_Learn_FeaturesOptions_Performance_S- HAWD_SHAWDOverview http://world.honda.com/HDTV/news/2004-4040401a/ http://en.wikipedia.org/wiki/SH-AWD Bob |
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Bob has it right. SH-AWD "overdrives" the outside rear when cornering (via gear multiplication). The outside rear wheel spins faster and steers the back end through the turn, offsetting the inherent understeer in the vehicle. It works very well, and feels cool. The catch is that you need to power through corners to kick it in, and it takes some experimentation to find the sweet spot. It's very similar to modulating throttle to control over/understeer on a RWD vehicle. Regarding VDC-AWD, I believe it does away with limited slip diffs, instead using open diffs and the application of brakes (traction control) to clamp down on spinning wheels. As you probably know, the benefit of a LSD is that it mechanically transfers power from a spinning wheel over to the other wheel on the axle, thus conserving 100% of the power that goes to the axle (it all goes to the wheel with traction in the event that one wheel slips). With the open diffs in VDC, the brakes clamp down on a spinning wheel and there is no mechanism to transfer that wheel's power over to the other wheel. Thus, only 50% of the power going to the axle can get put down to the road when one wheel slips. Now, VDC has some smarts, and it will hunt around for traction by braking/releasing slipping wheels. But in that situation, no more than 50% of the power going to an axle gets to the road compared to the 100% an LSD can manage. Craig
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Replying to: c_hunter (Feb 18, 2007 2:02 pm) -mike
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Replying to: paisan (Feb 18, 2007 2:55 pm) As far as I know, Subaru's diffs are open with VDC-AWD and there is nothing else to flip power to the other side. The reason the simple braked systems do heat up is that the brakes are resisting some or all of that 50% power to the spinning wheel. I guess that's a good way to categorize the systems. If they don't heat the brakes, then some other mechanism is transferring the power away from that wheel. If they do heat up the brakes, then the brakes are eating that wheel's 50% power.
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Replying to: c_hunter (Feb 18, 2007 3:50 pm) -Mike
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Replying to: paisan (Feb 18, 2007 3:59 pm) With no traction control intervention, a single slipping wheel will cause almost none of the torque to get to the ground. In that sense, it leaks out all of the torque. What does get to the other wheel is not enough to move the vehicle forward. When traction control clamps down on the spinning wheel, it artificially raises the level of resistance on that axle which then allows an equivalent amount of torque to go to the other gripping wheel where it can bite and rotate. Here's an explanation that's written far better than I could do: http://en.wikipedia.org/wiki/Differential_%28mechanics%29#Loss_of_traction Craig
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Replying to: c_hunter (Feb 18, 2007 6:55 pm) -mike
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Replying to: paisan (Feb 18, 2007 8:53 pm) Craig |
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Replying to: c_hunter (Feb 17, 2007 9:25 am) Nice pics! The RDX looks fantastic. I've seen quite a few in my area and I like the looks -- a more taught balanced version of it's bigger sibling. ken |
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     The rest are here: http://www.pbase.com/paisan/vir0207&page=all
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