NGZ

iTrader: (1)

Hi Tubbs, I have had the same experience.
Were you trail braking? If you were, then I believe it was ABLS that kicked in, and not VDC. It does not like it when your foot is still on the brake when you are cornering (no matter how lightly you are touching the brake). It tries to pulse the brakes, and if you have upgraded brakes, it's gonna grab that much harder.

Also, do you have handling mods? I suspect that mods throw the system off a little. The only time I couldn't reproduce it was when I had a passenger in the car. I haven't pushed the car much lately, so that's where my investigation has left me Although, I have found that you can disconnect the yaw sensor from VDC/ABLS.

Tubbs

iTrader: (1)

not trail braking. I only had the foot on the gas.

I have Zeal coilovers at 12/10kg and 1.5 degrees of camber all around. I was corner balanced with 1/4 tank and only me. And I was carrying more weight since I had the spare, 3/4 tank and the gf (and dog).


You are undoubtably right about the mods changing the car. I know for sure that I have a much more neutral car than before. I fully intend to have the *** slide a bit. That's no prob, but having the electronics do everything you DON'T want them to do is scary to think about.

The button goes off from now on. I see absolutely no reason to use it.

inanabhay

there are previous threads about VDC acting up - Tubbs is not the only one to experience this

NGZ

iTrader: (1)

AFAIK, ABLS stays on even with VDC off. I've been able to reproduce what you've described at fairly low speeds too. It feels like the car's electronics get confused and think you are slipping, when you know that the car can go faster.

Tubbs

iTrader: (1)

Have you ever experienced when the car starts to hydroplane and it hits the brakes? **** me. I would really like that to NOT happen. I would just like to continue driving straight and with gas pressed to go over the puddle.

NGZ

iTrader: (1)

When I looked into this some time ago, I found that some people wire a switch serially on the Orange wire (to cut power to the yaw sensor). If I remember correctly, doing this also makes the Slip light come on. But the result is that the VDC/ABLS system doesn't get any input from the yaw sensor, and this puts the task of cornering entirely in your hands.

Tubbs

iTrader: (1)

I might have to do that, thanks.

SirSpeedyZ

iTrader: (10)

either your car is possessed or you did something wrong

LeMans 05

iTrader: (1)

God was trying to smite you.

j/k, glad you're alright. While I've never had the VDC try to kill me, I don't think it's perfect. Once in the rain on an on-ramp I lost the rear (car was new, and I was putting too much faith in the VDC system), I was trying to counter-steer into the slide, and it felt like the VDC was fighting me the whole way. I wasn't thrilled by having the control taken out of my hands. Other than that, I haven't experienced what Tubbs did. I just hate it when the TCS goes off on a spirited 1-2 or 2-3 shift, and shuts down engine power. Embarrassing.

zedated

I think you've hit on the problem. VDC is to counter-steering... the way that ABS is to pumping-the-brakes. Before ABS, we were taught to pump the brakes to prevent forward sliding on ice. More specifically, we were taught NEVER NEVER slam on the brakes. Now, we are taught to slam the brakes and let ABS pump for us. This is a complete reversal of earlier techniques.

Likewise, we were taught to counter-steer into the slide to stop a sideways slide. Now, we're taught to point the wheels in the direction you want to go and let VDC do the correction for us. Again, this is a complete reversal of earlier techniques.

At least, this is my understanding of VDC. Let me know if this is wrong.

LeMans 05

iTrader: (1)

You may be right. I guess we're going to have to get used to it. Won't be too long before we won't be able to turn off the VDC at all. Government will regulate that, too.

Tubbs

iTrader: (1)

you're probably right. the next car I buy will be a Lotus. I'm sick of electronic crap.

NGZ

iTrader: (1)

Thread talking about different ways you can disable VDC (completely):
https://my350z.com/forum/2003-2009-nissan-350z/138480-how-do-you-disable-vdc-completly.html

Spike100

I remember viewing a video clip on Nissan's website back in 2003 when I bought my first Z. I am sure there are other readers here who may also remember this. The video clip shows a Z running all out on narrow streets in a city in Europe (I think it was France or Belgium, but not that's important). The Z car is going very fast, lots of shifts in twisted turns, great engine sounds, etc. The clip displayed the usual disclaimers (don't do this, professional driver, streets cleared and controlled, blah...blah), but also added that Vehicle Dynamic Control was off.

I bought a Performance model (which has VDC). I've always considered the disclaimer on that clip when deciding whether or not to have VDC on or off. My instinct is VDC should be on when driving normally with a stock or Nismo setup (wheels and tires). But, seeing Nissan's professional driver turn VDC off when driving the car very hard in the video clip I mention... well, looks like a "no-brainer" decision to me.

I usually have VDC on, and always on when driving "normally." Of course when driving conditions are poor (rain, bad road surface, etc.), I'm driving more slowly and always have VDC on. VDC has been really helpful on two occasions in my personal experience (but two times is not statistically significant). But, when driving hard, I always turn VDC off (as Nissan's professional driver elected to do in that video clip).

I believe Tubbs is correct. If you are driving the car hard and you are an experienced and capable driver, VDC "may get in the way." Here is a scenario and two different solutions/outcomes. You are in a tight turn with lots of speed, and the rear begins to move outside the radius (you begin to enter a possible rotation):

1) You do a gentle counter-steer, apply power, come out of the turn, and continue onward and forward.
Or...
2) VDC kicks in, kills the throttle (via TCS), brakes at the appropriate corner(s), stopping and straightening the car. You are pretty much sitting still at this point, but you are saved from crashing.

There is no way of telling for sure, but I believe that Tubbs experienced #2 in this scenario (because he had VDC on). I have no doubt that Tubbs is a very proficient driver who would easily execute #1 in this scenario. I am sure this would be his preference. I don't think Tubbs would have crashed, and I doubt VDC was helpful in this case.

--Spike

Tubbs

iTrader: (1)

I didn't know that, but I'd have to agree.

I always try to turn it off too, but coming from old school vehicles, it's difficult to remember turning driving aids off.


I did experience #2, and would have preferred #1. However, I also believe if I had let the car "do it's electronic wonders" I would not be here right now.

Thanks.

Spike100

Some other thoughts about your incident and report. There might be more than "meets the eye" here.

You reported a brake lockup that was quickly discounted by some other readers who said that cannot happen because the Z is equipped with ABS. Under pressure from this "for certain it couldn't happen statement" coming from respected posters, you said it felt as though the brakes locked-up. But, I think you really believe the brakes did in fact lockup.

I can say for sure (because I experienced this), you can have a "pseudo brake lockup." Here is why I say this. A couple of months ago I mounted new Goodyear Eagle F1 GS-D3 245/45-18 on the rear and the same tire sized 245/40-18 on the front. So, I have a similar wheel/tire setup as you as to width, and only differs from yours in that that my setup has closer to the OEM overall radius front to rear. After leaving the shop, I wanted to test these new tires. I mean... new tires... you gotta test them. I picked a roadway I knew well and felt I could do a quick test. In retrospect, that was very foolish. New tires are slippery and need some "break-in." Anyway, I did slip a little (VDC was on) in the first turn. I immediately felt the "ABS grind," but almost instantly after that, I felt as though my rear brakes were locked-up (same as you reported).

I think I know what happened (and guessing that might be what you felt as well with your brake lockup). VDC was on, quickly captured a problem, and went to work by cutting power and applying breaking to different wheels. I initially felt the ABS "grind," but also could feel a lockup. My guess is the "lockup" was not really a lockup, but only felt that way as VDC began applying braking to different corners. ABS was working, but VDC was also applying braking, giving the false impression I was locked-up. I am fairly certain that is what happened in your case. The breaks weren't locked, but it sure felt as though they were.

I agree with you. The driver feel helpless when the car shuts down its "life support systems," and you are unable to accelerate and steer under power.

I usually have VDC on, but there are cases where it should be off.

--Spike

Tubbs

iTrader: (1)

Interesting thoughts, and probably true. Thanks.

Kolia

iTrader: (2)

It's impossible to know exactly what happened from reading a forum topic.

Obviously, Tubbs is either missing something he didn't notice in the car's behavior or road layout, or it a system malfunction from the car. In either case, data logging would help.

Here's a few more thought. Running the square setup (no stagger front to rear) will mess up the electronics. The rear wheel will always be spinning a bit faster than expected and thus will be that much closer to the threshold limit where VDC/TCS/ABS kicks in. These systems are not designed to react to a spin/lock up. They are design to detect the impending spin/lockup. They kick in before we lose traction.. They do so mainly with individual wheel spin, monitoring accelerations in multiple axis, and compare that to brake pressure and steering angle. With these, it knows where the car IS going and where the car SHOULD be going. It will allow for some slip angle/skid (a few degrees) before taking over.

So, running a non staggered setup is messing the data the system gets.

Back to the topic at hand. Again, I don't know what happened. I do know of one thing that could have happened and that would have really pissed the VDC off. Anticipation of a skid from the driver. Tubbs, if you sensed the rear was about to loose traction and anticipated the skid with the slightest amount of counter-steering that would raise a big red flag in the VDC. You'd be turning left and suddenly steer to the right. VDC sees the difference between the car's attitude and your intended direction (it can't know you want to keep on going left) and will cut power and apply some front right brake.

VDC isn't so bad, if you understand how it works and adjust your driving to fit.

Spike100

^^ Good points.

Older drivers (like me) who started driving in the early 1960's (when almost all cars were RWD and there was no such thing as ABS and electronic stability control) were trained to pump the brakes (to avoid locking-up) and counter-steer in a skid to realign the car to the intended direction of travel. Of course with modern cars equipped with ABS and electonic stability control, you do just about the opposite: Stand on the brakes and allow ABS to do the "brake-pumping," and keep the front wheels pointed in the same direction you want the car pointing (i.e., no counter-steering).

In the two instances (not the minor instance I describe above which was only momentary) I have experienced a "full engagement" of VDC, VDC (and its "sub-component," TCS) went to work before I even knew I was about to begin rotating. Before I could do anything such as applying the brakes or counter-steering, VDC (via TCS) killed the power and VDC's electonically-controlled braking aligned the car to the front wheels' direction. It happened so fast I couldn't react, and only found myself safely almost stopped and pointed in the correct direction.

Nissan says you should use VDC with the stock wheel/tire setup; or the Nismo tire/wheel, swaybar and spring/shock setup. That setup is staggered in both width and overall diameter, front to rear. I guess they test only these two configurations with VDC, and that is the reason for this recommendation.

Tubbs is square all around (width and overall diameter). I am pretty sure Nissan would say this setup is not tested; and therefore, not recommended. I doubt they would go as far as saying it won't work at all. I would think Nissan would also say the same for my setup (245/40-18 front and 245/45-18 rear) since it is not staggered width-wise front to rear.

For daily driving, I will keep VDC on (even though my tire/wheel setup differs slightly from stock and Nissan's recommendation). VDC has prevented me from hitting the guard rail twice now, so I consider it a "guardian angel."

And, I do agree with Tubbs' thinking that VDC should be off when doing faster driving and hitting corners hard. I have no idea if VDC works as Nissan intends under these conditions (high speed driving); but like Tubbs says, the driver should be in control. And, a good driver can do this without depending upon the electronic controls (which could possibly interfere in this case).

--Spike

PDX_Racer

iTrader: (2)

VDC does work as intended, but I know that there have been times on an autocross course (when it's dry) where I'm actually *ahead* of the VDC, so its annoying.

Probably the most annoying is the combination of VDC and EBD. It can really make the car seem like it has a mind of its own.