Traction control & some advice please!

[Anonymous]

Funny thing happened on the way into work this morning; totally dry road, long sweeping bend leading onto the motorway, nobody else about, hard acceleration through 2nd and 3rd, into 4th, traction control light starts flashing. No loss of grip, carried on with foot planted and it still flickers for a good couple of hundred yards until the road straightened.

Now, I'm on pretty new Bridgestone RFT's on the rear, (like 200 miles old) but they should be scrubbed by now (I think?) and nicely heated as I'd already done a good 5-10 miles since leaving home.

Don't get me wrong, the car felt totally planted, no loss of grip, not even a even a twitch, but traction control kicking in on a dry day in 4th gear? Is it me?

Thanks for all help.

Cheers

E's Dad

 

[ovrkll]

Had this happen a few times myself, I think it is the car sensing lateral acceleration in the corners and applying itself to insure that the car makes the turn safely without loss of control. If DSC was off, you may have started to experience some sliding issues, but unless you were really pushing it, I doubt it. The DSC is programmed to detect certain levels and kick in, which can be quite intrusive at times if it happens when it is unexpected. So, no, it was not you, just our Z's

 

[fire-n-ice]

yep, what he said ^^^. I pushed 100+ on a mod. curve and finally experienced some sliding w/all the nannies on a couple months ago. It's the hardest I've ever pushed and also was the greatest adrenaline dump I'd had in a while - takes a lot to get my blood going . Good driving skills along with our baby-sitters makes for extrememly fun/safe street driving. Be careful and enjoy, these cars are funner the more you do with them.

 

[Anonymous]

Thanks a lot guys, I feel a lot better now. Of course I wasn't pushing 100mph, honest officer!

 

[AlanL]

yep, what he said ^^^. I pushed 100+ on a mod. curve and finally experienced some sliding w/all the nannies on a couple months ago. It's the hardest I've ever pushed and also was the greatest adrenaline dump I'd had in a while - takes a lot to get my blood going . Good driving skills along with our baby-sitters makes for extrememly fun/safe street driving. Be careful and enjoy, these cars are funner the more you do with them.

Hmmmm - 100+ out on the streets??

olice: BUSTED!! olice:

:telloff: :telloff:

 

[The HACK]

Had this happen a few times myself, I think it is the car sensing lateral acceleration in the corners and applying itself to insure that the car makes the turn safely without loss of control. If DSC was off, you may have started to experience some sliding issues, but unless you were really pushing it, I doubt it. The DSC is programmed to detect certain levels and kick in, which can be quite intrusive at times if it happens when it is unexpected. So, no, it was not you, just our Z's

The car's not THAT smart. It uses primarily the ABS sensor to sense slip in any of the wheels to determine if it needs to cut power or apply brakes to bring the car back in-line with the steering angle.

My guess is that, if it's a heavily banked turn, and the OP got on the throttle aggressively, all it's doing is cutting back engine power to prevent the rear from swinging around. Sounds to me like someone's got a bit of a lead foot and don't know the difference between a hole in the ground and an apex.

 

[ovrkll]

Sounds to me like someone's got a bit of a lead foot and don't know the difference between a hole in the ground and an apex.

Yes, I know what is in these cars, and I know about an apex, which is all well and good, except when the turn is 270 degrees.
Straight from BMW:

Dynamic Stability Control

Dynamic Stability Control is an innovative technology that combines the functions of traction control, braking enhancement, and cornering stabilization. DSC sensors continually monitor cornering-steering angle, transverse acceleration, yaw, wheel speed and brake pressure to instantly detect and correct loss of wheel traction due to slick spots, nasty weather, or emergency maneuvers. DSC helps you stay in control under all conditions, in any situation.

 

[The HACK]

Sounds to me like someone's got a bit of a lead foot and don't know the difference between a hole in the ground and an apex.

Yes, I know what is in these cars, and I know about an apex, which is all when and good except when the turn is 270 degrees.

Huh? A 270 degrees turn still has a turn-in, apex, and track out. Sounds to me like someone REALLY don't know the difference between a hole in the ground and an apex.

For a 270 degrees turn, the same driving principles apply. The double cone on the diagram denotes where you need to start braking, the next single cone is your turn-in, the single cone on the inside of the turn marked "apex" is your apex, and the single cone on the outside just before the underpass (or overpass) is your track-out.

The green line is when you're accelerating. The red is braking. Yellow is neutral throttle (meaning you apply just enough throttle to keep your speed through the turn constant). Where it transitions from yellow to green just before the apex is where you actually apply throttle.

This is assuming a constant radius turn with equal and consistent camber across the "track" surface. Repeat after me, for every turn, there's a turn-in, apex, and track out.

Also, if you believe BMW's marketing speak, then I guess that's fine and dandy. But the system isn't as smart as you think it is. It is not capable of discerning lateral load vs. traction available. All it does, is if it senses one of the wheels slipping, it'll respond accordingly by selectively braking in that corner or cut power to the drive wheel. All the lateral load sensor will do, is compare its data against the steering yaw sensor and make sure that the direction of the load is consistent with the direction of the wheel is turned. The proof is when I'm driving on the banked oval of California Speedway, there's a tremendous amount of lateral load with VERY MINIMAL STEERING INPUT, yet DSC does not interfere. However it will interfere if I'm in the part of the banked oval where it TURNS, since the outside wheel needs to turn faster than the inside wheel.

I have a feeling that the OP was applying throttle where it's yellow in the diagram, and DSC is trying desperately to cut throttle to the drive wheels to prevent slippage, so despite the fact that DSC is intervening, it still "feels" like it's got grip. It doesn't.

 

[ovrkll]

I understand that, but the original posts were in regards to driving on roads and not a track. There is a lot less room for maneuvering unless all lanes (if there are any) are open, hence the propensity to push hard coming out of the turn and the likelihood of the DSC stepping in. Not everyone has track experience (or enough of it) to see a corner/curve and automatically know the exact line and amount of pedal and brake to use to achieve maximum results.

 

[fire-n-ice]

olice: BUSTED!! olice:

:telloff: :telloff:

Hey, I never said I was perfect :innocent: ...but I do appreciate the spankings!

 

[AlanL]

Always glad when I can help out.

opcorn:

 

[Rick Hunter]

opcorn: Sweeeeeet... keep it goin, boyz. I wanna find out who's gonna get wned: in the end. My bet's with The HACK FTW. :fuelfire:

 

[fire-n-ice]

Rick, what's FTW?? sorry, a little slow on all the computer lingo ldman:

 

[ovrkll]

^^ :lol: @ Rick

Okay since I work around accelerometers and gyros every day, here is a quick blurb on it:
"Transverse sensitivity is the ratio of the output caused by acceleration perpendicular to the main sensitivity axis divided by the basic sensitivity in the main direction."

So, the measurement taked by accelerometers used in our cars is ACCELERATION away from the main axis, not load (or .g's), the gyro detects yaw, and the ABS system detects wheel slippage. All data is fed into a PLC which has been programmed at a baseline level determined by BMW engineers. Any of these measurements that happen to fall outside of normal parameters will cause the DSC to engage. A case can be made where any of these can be exceeded, but you do usually have some wheelspin to go with it, so I see the reasoning behind thinking there is only an ABS sensor onboard. A little more in depth look at the uses of accelerometers can be viewed here:
http://www.willow.co.uk/html/oem_component_accelerometers.html

Now, remember that BMW programmed the system at a baseline level which does not take into account running stickier tires, upgraded suspension, etc. So the system may intrude at a point that wheelspin has not occured, but the acceleration rate of vehicle mass in a transverse direction, has triggered a DSC event.

 

[ovrkll]

Rick, what's FTW?? sorry, a little slow on all the computer lingo ldman:

For The Win

BTW, I am not trying to start or participate in a flame war. The HACK puts out some really good info as it relates to the track, but the demeanor that comes with it, is a little excessive. Belittling and ridiculing a person based on a simple question posed on this forum was a little over the top. There are no stupid questions on this forum, and we should all try to be as helpful as possible, even if you think the question was stupid. As the old saying goes, "if you can't say anything nice, don't say anything at all". :wink:

 

[Anonymous]

Thanks everybody for all the advice and support.

You know, when I wrote it, I thought somebody might try to rubbish my driving skills, or possible lack thereof. To be honest, it does make me think twice about asking this sort of question in future

We aren't all Lewis Hamilton's and before anybody says "well you shouldn't be pushing that hard on the public road", I did make the point that the road was empty, the worse that would have happened was I'd end up with egg on my face and my own pride and joy in a mess.

Bottom line is, I know my driving limits are nowhere near the ability of this fabulous car.

Take care.

E's Dad

 

[Color]

Hi Ed's Dad,

We are a pretty friendly bunch on this forum and you usually you get your questions answered without any ridiculing or rubbishing, or they are in a friendly joking manner, so don't feel discouraged by this one event.

Seems theHack feels he has superior driving skills and needed to show that.
Nothing wrong in that part, but obviously the demeaning part was totally unneccesary. :thumbsdown:

Hope to see you around more

 

[fire-n-ice]

Ethansdad: You've always been respectful here, your questions are very much welcomed. We all can learn something from everyone, no matter what your experience may or may not be. Gaining that experience must come from somewhere, and sharing them here is an excellent source. It was a very valid and legitimate question, and I appreciated it. My paramedic instructor used to always say: "The only stupid question is the one not asked".
Keep 'em comin', that's what makes this forum so great
T.

 

[fire-n-ice]

obviously the demeaning part was totally unneccesary. :thumbsdown:

X2

 

[WLH]

but the demeanor that comes with it, is a little excessive. Belittling and ridiculing a person based on a simple question posed on this forum was a little over the top.

Agree as there is no place on this forum for personal insults to anyone...