MrWigggles

I was taking a tight hairpin turn last night and found out much to my surprise DSC and ABS wouldn't kick on at the same time.

I took the turn thinking hard braking is going to be needed. My ABS kicked in as needed but as I started to turn the DSC came on a little unexpectedly. I don't think I really needed the DSC much for the turn, but the bad news was suddenly my ABS stopped working when the DSC came on. The result was that my 8 was suddenly sliding towards the outer curb at the apex of the turn instead of going through the turn with some help of the ABS.

I was very surprised by the event and so was my friend in the car in front of me; we both heard the loudest tire squealing to ever come out of my car. The end result was I came 3 feet from the curb that I should have never been close to (I ride the inside shoulders in turns partly for the unexpected.

Different or similar stories please share.

-Mr. Wigggles

Maolin34

ABS is an integral part of the DSC system. DSC combines ABS, Electronic Brakeforce Distribution, and Traction Control into one system. ABS on it's own, simply responds to prevent any braking wheel from locking up. In doing so, the idea is to give you steering control by keeping the front wheels turning. At whatever point in the turn that DCS recognized the inputs that would lead to a slide...EBD kicked in to apply more braking force to one wheel, or one side to circumvent the slide. There is no perfect system to handle every situtation... for spirited driving, and more control over the attitude of the car, I turn DSC off, but not with the long button press. This leave traction control only, and removes some degree of EBD. The traction control will only address wheel spin, and there will be limited response to lateral movement. So, I would say that you were overdriving the car in this hairpin to have DSC active. Of course, I only have the details that you mentioned...without knowing the car understeered or oversteered it is hard to say for sure.

Based on what you have stated, I would say the car understeered. You plowed through the turn approaching the curb. Depending on your speed, road conditions, and several other factors...ABS alone would have probably left the same results. ABS will not continue until the car stops, it will only intervene when lockup is inevitable...old ABS systems would turn on like a switch, and not disengage until you released the pedal...new systems are able to engage and disengage based on realtime data.

MrWigggles

The ABS came on for only a brief millisecond before EBD came in did its own thing.

My rear end was going to come around. It was the EBD that made the car understeer as if it didn't understand that most of yaw the car was experiencing was actually due to the very tight turn not an uncontrolled slide. I know the car can't see the road ahead but can't it tell the position of the steering wheel?

If it helps you get a sense of what was going on, when the EBD kicked in, I felt like I was hydroplaning in quicksand even though the concrete was clean and dry and 60 degrees outside - plenty of grip but no controll a really weird sensation.

Bottom line the car was simply trying to slow me down not help me make the turn. In this case DSC made the wrong choice and I was lucky I left some extra concrete.

BTW, I leave the DCS in the default position because we get a lot a rain here in Houston and there is quite bit of standing water. I need DCS to be as responsive as possible - a hidden puddle at night can sneak up on you pretty easilly.

-Mr. Wigggles

fizzer

I always turn of dsc when trying to manuever near the limit (not too much on the street of course ). I think it guesses wrong as its logic is geared for reacting to emergency situations. If I were designing a DSC system I would have to assume that people would turn it off for high performance intentional maneuvers. Could be a liability issue as well...

beachdog

If this is an accurate description of the events, it sounds like you probably backed off on the brakes enough for the ABS to shut off. I'm assuming that even in the severe situation you were braking hard ahead of the turn and you let off on the brakes to dial in the turn. The ABS assumes that you have things under control if you let off the brake.

Yes, there is a steering angle sensor. The DCS triggered because of the steering angle and tire speeds being out of sync.

MrWigggles

beach,

If the steering wheel sensor indicated I was turning right, why did the car individually brake the wheels in a manner to prevent me from turning?

Slowing me down is one thing but it apparently applied disproportional amount of braking to the left side of the car to prevent me from turning right. My wheels were turned hard to the right and yet I (1) skidded straight forward while (2) the tires were screaching continuously. To reiterate it felt like I was hydroplanning in quicksand.

On dry pavement (1) shouldn't happen with a car with DSC and (2) shouldn't happen on a car with ABS. The DSC had my car going the wrong way with at least some of my brakes locked-up. I should have taken pictures of the continuous skid marks to prove it.

-Mr. Wigggles

Genom

Proof that the car doesnt know what your doing exactly and it reacted to what it thought was a different situation if you ask me. Sharp angle turn, different wheel speeds and heavy brakes usually means a spinout. I'm not surprised personally. I'd turned it off for a manuever like that.

JMD RX-8

Mr Wiggles

Is there any chance you steered into the skid, even unconsciously? That would make the car think you were trying to steer strait ahead, thus changing the way DSC engages.

clyde

Electronic aids don't overpower the laws of physics. You were going too fast for the turn and you pushed to the outside. Braking hard, and doing so when you did, only asked the tires to do more after they were already overloaded. Without DSC, you almost certainly would have spun and hit the outside curb/gone off the road backwards. The system did what it was supposed to do.

beachdog

Mr. W - try a similar maneuver in an empty parking field if you can. If it reacts the same way, have Mazda check the abs pump. There have been a number of failures noted on this forum. The abs pump activates for both the abs and the dsc.