[frosty]

Who can give us some info on the VDC system as in "control", not braking? (We all know about ABS.)

Where does "it" derive it's info?

How does it effect adjustment to control the car?

Is it better than human intervention in a slide?

What if "it" plus human intervention arrive at the same time?

What about the diff - is it "intelligent"?

More 'n more questions the more I think about it.

 

[harryw]

Shizzle, found this. Sorry i dont know enough about it to enlighten you any further.

As always

ME

VDC = Vehicle Dynamic Control. An onboard computer measures the individual rotation rate of your four wheels using the ABS sensor. It then compares the rotation rate to steering input, throttle input, and a yaw sensor (measuring rate of car rotation). Together, these inputs are compared to a pre-programmed algorithm that (hopefully) prevents you from losing control of the car in and adverse situation.

Example: You head into a sharp left hander hard on the throttle, turn the wheel left without lifting, and the VDC senses the rear of the car starting to fishtail to your right. VDC then takes control of your car to let you steer thru the corner by
1) retarding the throttle
2) applying the inside left rear brake

VDC DOES NOT prevent wheels from spinning; TCS does. Changing overall tire diameter ratio front-to-rear without reprogramming the VDC algorithm will screw up the intended operation of VDC as determined by Nissan.
HTH

 

[davidm]

Is it better than human intervention in a slide?

That depends on how you are at 'intervening' yourself. On the road, and in 'accident' situations it's a good thing as it will do it's best to stop the car from spinning. It does so by grabbing brakes at individual wheels as it deems necessary.

On the other hand what it does is stops the car from turning and does it's best to keep the car pointing (and hence going) straight. That means that if (in theory) you were trying to swerve around an object and got the car crossed up, then it will straighten you up and point you back into the object you're trying to avoid.

At the track (or skid pan), you try and drive the car all the limit and want a little bit of rotation from the car (ie. passive stearing through the rear-end sliding) ... in particular before the apex. Though, the VDC will do it's best to stop any 'shananigans' like this and will try and point you away from the apex (ie. out of the corner) ... which only slows you down and messes up your line.

What if "it" plus human intervention arrive at the same time?

You'll probably over-compensate. ie. you counter-steer at the same time as the VDC is stopping the car-rotation via the individual application of the brakes and hence the car will probably over-correct itself (unless you adjust your inputs quickly). I'm just guessing, the quickest (and smoothest) way to drive withthe VDC is to not counter-steer, and let the VDC sort out the slide. More or less just ignore the fact that the car is sliding. If the slide it throttle induced then VDC unless you have TC switche on, I don't think that VDC will cut power (and hecne you better do it).

In a way that is supposed to be the technique for driving 4WD cars at the track. You point the car and foor it. If the car slides at one end of the other then you just ignore it and let the computers and diffs sort it out.

 

[mr rizk]

I think you should be asking on how to turn it off completely :biggrin:

 

[frosty]

Thanks fellas.

So where's the "yaw" sensor?

What is it? How's it work?

How does the car apply a brake if that wheel is already sliding?

Can't find much anywhere about this hi-tech and interesting aspect of the car.

Plenty of info about trinkets for the car, not much about this.

Schizzle

 

[harryw]

Shizzle, I believe the sensor is in the roof.

I dont know much about it either!

As always

H

 

[scathing]

I'm not sure for certain, but if Nissan knows anything about cars they'll put the yaw sensor as close to the centre of gravity as possible. Its in that location that it can accurately identify the forces on the car.

As for braking, the sensors tell the computer whether its sliding because of too much speed or too little, and so it either clamps that caliper to reduce its spin, or unclamps the caliper to increase it. Of course, it will also act on the other calipers individually to try and have all four wheels matching their ideal speed (since your inside wheels should be rotating less than the outside ones) as quickly as possible.

As for the diff, its a viscous coupling. I remember reading somewhere (probably Motor or Wheels) that it was using a helical (or torsen) diff, but when I was looking around earlier it turns out its a viscous coupling. I've been lead to understand that the viscous diff is pretty weak, which is why the GT-R and S15 200SX's run helical ones.

If anyone in Sydney replaces their diff with a clutchpack one, can you take me for a ride (or, better yet, let me drive it) to see if its a worthwhile upgrade? The KAAZ or Cusco LSD costs around $2K, so I don't want to find out that it comes on too suddenly and strong, and isn't a good "streetable" diff.

 

[frosty]

So yer racin' a "newbie" in an old red Z down the M3, and the raw sensor malfunctions - the front wheel locks up!

WTF then ! ! ! !

Oh, of course, that can't happen - its NISSHIT - HOORAH.

Who's comin' ter the funeral?

F
R
I
Z
z

l

 

[apsilon]

Originally posted by frosty@Nov 4 2004, 10:47 PM
What if "it" plus human intervention arrive at the same time?

I experienced that scenario a few times. It's not a happy experience.

Basically DavidM was right. You end up over compensating. It almost sent me off the road so after that I turned it off every time I got in the car.

 

[Nuff]

Frosty, the g-sensor is next to the handbrake, and if any subsystem of VDC melfunctions it's supposed to disable itself. One way of disabling VDC totaly is if you unplug it.

 

[scathing]

Originally posted by apsilon@Nov 5 2004, 02:19 AM
You end up over compensating. It almost sent me off the road so after that I turned it off every time I got in the car.

What shits me off even more is that you can't turn the VDC off completely. Its the major reason why I didn't buy the Track. Bolt-on diffusers and brakes are far easier to do than buggering around with your electricals, and then hoping that splicing the VDC wiring doesn't cause the entire thing to fall over and stop the car from working.

You'd think that Nissan would learn that some systems aren't appreciated in sports cars that attracts a sports clientele after HICAS. Thank God that's not in the car too.......

 

[db350z]

Now you mention it. Is this the reason we track owner can't beat Lionking Touring Auto on the drag race?

 

[davidm]

So where's the "yaw" sensor?

From what I gather, it's where Nuff mentiones. ie. where the hand-brake is.

How does the car apply a brake if that wheel is already sliding?

It will not apply the brake tothe wheelthat is already sliding ... that would only make the slide worse. What it will do is apply a brake to the opposite wheel, which will straighten the car up. Picture this - your back steps out to the left as you lost traction on your rear-left (ie. car is rotating clockwise). The VDC will apply brake to the right-rear as well as left-front (that is to slow down the wheel rotation, not to lock up the wheel). This will create an anti-clockwise rotation of the car and hence straighten it up. Pretty clever stuff, but **** annoying when you're counting on the original slide to get you around a witches-hat on a skid-pan

What shits me off even more is that you can't turn the VDC off completely.

Youu can pull out one fuse and the VDC and TC will be 100% disabled. The only problem is that the ABS willbe disabled as well. Well, and that your dash will be light up like a Christmas tree.

Though, when in the 'off' state, the VDC will not intervene unless you hit the brakes.

Is this the reason we track owner can't beat Lionking Touring Auto on the drag race?

LK was getting superior 60' times than the rest of us ... that is why he whooped up on us. The taller 3rd gear and 7,000rpm cut-out helped, but it was really the launch that made all the difference. I read somewhere that every 10th that you can cut-off from your 60' time will translate to two 10th at the end of 400m.

 

[mchapman]

Incase you hadnt seen.

Nissan VDC Animation
http://www.nissan.com.au/z/flash_popup_vdc.asp

VDC (Vehicle Dynamic Control)
The quicker you go, the quicker you can get into trouble. Vehicle Dynamic Control (VDC) is there to help. It's a system that instantly senses when the car is losing its intended line of trajectory and what needs to happen to help remedy the problem, reducing engine torque to specific wheels and applying braking as necessary.

 

[zuffy]

I could be wrong but maybe the VDC is the problem when we used to complain about understeer.

Since i've got so used to turning it off and i brake less around corners i've noticed less understeer. (best motoring pointed out VDC never fully turns off, and uses braking input.)

I find that with VDC on the car has 4wd type of characteristics...without the extra traction.

I leave it on in the rain only.

BTW have you noticed that if you hold the VDC button long enough the light turns off and won't come back on until you turn the ignition off? 2 stage VDC switch?

 

[Perth 350z]

That's right Zuffy - It is a 2 stage switch. I remember reading about it a Motor mag ages ago. I don't believe it's in the manual, but they did state that they kept the button pressed for "several seconds" to completely disengage the VDC

 

[davidm]

I don't believe it's in the manual, but they did state that they kept the button pressed for "several seconds" to completely disengage the VDC.

I don't think that it disangeses it properly as I think I tried it. Still, don't take my word for it as as I was trying everything I could think off when I even pulled out the fuse ... might have missed someting. Will try it again when I get the chance.

I could be wrong but maybe the VDC is the problem when we used to complain about understeer.

Not for me. I can disctintly feel the difference when the front tyres loose grip (ie. understeer) and when ther VDC kicks in. The VDC has a very artificial feeling, while the understeer that I used to complain about was pretty natural feeling of loss of grip.

Also I did leave the VDC ON once when I was doing a 'cone dodging' run on a skid-pan (ie. DECA) and you instantly feel when the VDC is working against you.

ps. I leave it in the OFF mode on the track and it does not seem to come on unless you're trying to trail-brake deep into the corner and hence are also turning in. That is annoying, and in turn I find myself trail-braking less. Will report more in a week, when I get back from Winton.

 

[scathing]

The understeer is inherent in the car.

My car has no VDC and it still understeers mightily, especially on a wet skid pan.

I get the feeling its just us, though. The car is set up with a wider rear track and front heavy, and making a car nose heavy and providing more grip at the back is hardly going to make it inherently darty in corners.

I get the feeling that you just need to learn the car, and you can dial most of it out. I remember how heavy and unwieldy the 350Z felt when I first took it for a spirited drive, but then I was trying to chuck it around like my Pulsar SSS.

The Z is a car that encourages you to drive properly (or punishes you for not). Once I learned to slow a little more for the corner, trail brake if necessary, and be smoother on my turn-in inputs, and then rely on the copious rear-end grip when I power out from the apex, the car is quite responsive and quick. 1500kg is never nimble, but you can go quite quick.

Of course, if you have VDC then the option of trail braking isn't there for you......

I went up on the Old Pacific Highway last weekend, and I drove with a friend in an S15. His car makes around 170rwkW (so more than mine does) in a 1300kg package. He also has brand new tyres. On the open, sweeping sections up to the Calga Interchange, I'd get away from him. If the straight was the right length, he'd catch me. On turn-in he might make a smidgeon of gap on me. On exit, I'd pull away. Where I can floor the throttle in the meat of third gear and be sitting there begging for more power, he has to feed it in gradually or risk the rear breaking away.

Once we went north of Calga and the road tightens up a lot, however, it was another story. I was fighting the car and trying to keep it from understeering off the road, and he was driving at 6 tenths to avoid running into the back of me. At that point, the extra 200kg becomes telling.

 

[frosty]

Still dunno what the "yaw" sensor IS - ie, is it a gyro or a mercury switch or what?

Seems to me such a major piece of technology having such massive effect on the performance of the car should be better documented and understood.

Might have to post on the international forums to get some info?

SCHIZZLE

 

[mr rizk]

Originally posted by Perth 350z@Nov 6 2004, 12:21 PM
That's right Zuffy - It is a 2 stage switch. I remember reading about it a Motor mag ages ago. I don't believe it's in the manual, but they did state that they kept the button pressed for "several seconds" to completely disengage the VDC

The BMW are like this but not sure about the Z. I think I tried ages ago holding it down like mentioned but I had issues. Can't remember what though