Beanboy Posted April 17, 2006 Share Posted April 17, 2006 Mentioned in other threads by various folks, figured big enough to have own thread. New Legacy Spec B has VDC and a 6-speed manual, along with a torsen limited slip rear diff. Still a viscous limited slip center diff with a 50/50 split. How does stability control work with a "dumb" speed-sensing limited slip center diff? Can see how it works if all wheels are moving. But in a situations where stability control can help, axle speeds can vary greatly, and cause that vc to start to lock just as one or two individual brakes are activated by the stability control. The two will be fighting each other... Enough give in the vc unit? Stability control not active long enough to cause any undo stress of vc? What am I missing? -B http://www.standardshift.com Link to comment Share on other sites More sharing options...
jsalicru Posted April 17, 2006 Share Posted April 17, 2006 yay.. you, like Subaru, didn't bother to mention that it gets a open front diff... This tranny is nothing to be excited for.. except the extra gear. They could have simply slapped the limited slip in there but why do that when you could comform with the STi. "some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose." Link to comment Share on other sites More sharing options...
Beanboy Posted April 17, 2006 Author Share Posted April 17, 2006 Well stability control is a biggie, especially since this is the first implementation on a traditional Subaru manual transmission application, something I didn't think possible. I also can't think of another implementation of a speed-sensing mechanical limited center diff with stability control. -B -B http://www.standardshift.com Link to comment Share on other sites More sharing options...
jsalicru Posted April 17, 2006 Share Posted April 17, 2006 I don't think its really an issue. Porsche uses the same thing... here's the literature on Porsche's webpage. The sophisticated all-wheel-drive system that transfers power onto the pavement with conviction on new Carrera 4 models has been augmented by enhancements to the Porsche Stability Management (PSM Plus) system. This system lends even higher levels of performance to the 911 models robust braking system. In addition to the litany of handling improvements highlighted on the previous pages, the all-wheel-drive version of PSM offers two additional functions that work in concert with the 911 braking system to shorten stopping distances. Should the driver suddenly release the throttle, PSM Plus automatically increases pressure in the brake lines slightly to eliminate the air gap between pads and discs. If the driver then applies the brakes, the response from each caliper is that much more immediate. In an emergency stop (when the pressure on the brake pedal exceeds a predefined threshold), PSM Plus initiates full ABS braking to apply maximum stopping force at all four wheels. Working in conjunction with the Carrera 4’s variable differential, PSM Plus combines improved driving dynamics and greater agility with exceptional vehicle stability. In short: improved performance with enhanced levels of active safety. At the center of the Carrera 4’s intelligent all-wheel drive is a viscous clutch that reads traction at all four corners and instantly transfers an additional 5 to 40 percent of the engine’s power to the front axle for maximum grip, even on changing road surfaces. The multiple-disc clutch consists of a series of interleaved plates. The space between these plates is filled with a high-viscosity silicone fluid. If the front and rear axles begin to rotate at different speeds, the frictional properties of the silicone fluid cause torque to be directed towards the plates that are rotating more slowly. At least 5 percent of drive torque is applied to the front wheels at all times. Under daily driving conditions, the average rear/front torque split is approximately 65/35, resulting in laser-true tracking at speed and unprecedented control through the tightest corners. "some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose." Link to comment Share on other sites More sharing options...
Ken S Posted April 17, 2006 Share Posted April 17, 2006 That's been my question too. VDC, until now, has required VTD. One of the differentiating features of VDC compared to other ESP systems was that VDC could control the torque split in addition to braking individual wheels. I'm interested to know what changes Subaru made to accomodate the VC. I've read that Subaru had to tune the VC characteristics so it wouldn't react as quickly when ABS kicks in. Perhaps they did the same with the Spec B implementation. Ken Link to comment Share on other sites More sharing options...
f1anatic Posted April 17, 2006 Share Posted April 17, 2006 maybe it helps having drive-by-wire and the computer can prevent any significant amount of torque going to the tranny regardless of the pedal input from the driver. . Link to comment Share on other sites More sharing options...
Canuck 2.5GT Posted April 20, 2006 Share Posted April 20, 2006 Will we be able to turn off the stability control? Will it effect snowy donuts in the winter? Link to comment Share on other sites More sharing options...
mwiener2 Posted April 20, 2006 Share Posted April 20, 2006 The VDC works by braking individual wheels to prevent and try to correct under/oversteer. It works the same on a 2wd car as it does on an AWD car. The system actually fights against the AWD in certain situations which is why they kept the viscous diff. It can absorb the binding a little. The VTD diff would simply open up when the VDC kicked in. I'm pretty sure the VDC isn't meant as a traction control feature for finding straight line traction, it's for keeping the car on the road through turns and sudden manuevers. and yes, there's a button to turn it off My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
Ken S Posted April 20, 2006 Share Posted April 20, 2006 I think Subaru needs to update their explaination of VDC: http://www.subaru.com/shop/overview.jsp?model=B9_TRIBECA&trim=7-PASSENGER&command=overview (click on Symmetrical AWD link)-->"what's the difference?"-->VDC "VDC works in conjunction with the VTD AWD System...." Link to comment Share on other sites More sharing options...
BOY Posted April 21, 2006 Share Posted April 21, 2006 I have a similar debate going on NASIOC right now. Did Subaru misspeak the VC diff for the spec.B or did they dummy down the VDC? VDC does talk to the VTD controller in every other application, why the change? Link to comment Share on other sites More sharing options...
fzanetti Posted April 27, 2006 Share Posted April 27, 2006 I have a similar debate going on NASIOC right now. Did Subaru misspeak the VC diff for the spec.B or did they dummy down the VDC? VDC does talk to the VTD controller in every other application, why the change? Also curious to know why!!!!! Flavio Zanetti Boston, MA Link to comment Share on other sites More sharing options...
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