ESP

[fka]

Is it feasible that ESP would kick in whilst taking a sharp bend on the MWay at relatively high speed in dry conditions?
I've noticed on two or three occasions what feels almost like a gentle wheel wobble when cornering like this. The car holds firm to it's line and there's no vibration or feel of anything odd through the steering wheel and the rear end feels solid ( ). At first I assumed it was just an uneven road surface but have since wondered if it could be ESP tapping on the brake on a wheel?
I've powered round a few roundabouts to the point ESP has kicked in but it seemed more linear/progressive.

[Audax]

That's how ESP works, it's entirely feasible that the car starts seeing potential for an event happening long before you do and long before it needs to actually do something. However the car doesn't know that the road is dry or what state the tyres are in or if you'll do something crazy with steering inputs so it will do lots of corrections early on before it has to do a major one.

[fka]

Having spend a good part of last night reading up on ESP, that's what I assumed was happening. On each occasion I was on the limit of what you might consider comfortable. So I presume the chassis roll and yaw sensors at this point would be indicating to the controller that it needs to intervene?

[Audax]

The control module will make all the decisions, the inputs are steering wheel angle, yaw sensor, pedal positions, wheel speeds. There is no sensor for chassis roll.

From those inputs the controller will know which parameters are "safe", these will have been worked out from a bunch of inputs that will have been defined on a test track and in simulations and then tested heavily. The controller will be monitoring so that when one or more of the inputs shows something being out of spec it can then take corrective actions based on that such as braking individual wheels or sending a message to the engine ECU to reduce power. Off the shelf the Bosch system will work without much adaptation but it can be tuned... Saab were at that time one of the few companies who took the system from Bosch and then did their own testing and integration to improve the way the software did the calculations, this would be things around how the chassis performs, weight of the vehicle, performance of the brakes etc. etc.

[fka]

I thought I'd read something about a sensor measuring roll, maybe from another manufacture's car or possibly from someone less informed..
That's really interesting about Saab tweaking the Bosh system. Amongst other things I've read a lot of "Joe Bloggs Internet Warrior" stating that they don't trust computers etc etc .. "I always turned ESP off, I'm a far superior driver.. etc etc .." I wonder of in fact there is some truth that the system doesn't work so well with certain manufacture's cars, as they use the off the shelf solution?

[Audax]

Amongst other things I've read a lot of "Joe Bloggs Internet Warrior" stating that they don't trust computers etc etc .. "I always turned ESP off, I'm a far superior driver.. etc etc .." I wonder of in fact there is some truth that the system doesn't work so well with certain manufacture's cars, as they use the off the shelf solution?

It's complete nonsense, the ESP system can brake a single wheel (or opposite wheels etc.) to adjust the direction the car is moving in, a human driver can't do that. The only case I can think of where a human driver could be better would be if you had something like a rally car where you want to deliberately upset the balance and direction of the car to do stupid things to move along faster based on the road you can see ahead, that's not something I would want anyone doing on the same roads I'm on!

One "test" I did in a 9-5 Aero with summer tyres was when it was around -10°C and very very icy on an ungritted road and I put my foot practically flat on the floor and the car very slowly drove itself down in a mostly straight line the road while the brake controller was going absolutely nuts, I then tried to drive in a straight line down the same road with the ESP off, it was not easy to do that.

[fka]

I've watched a few of the demo videos on ice/snow and skid pads, there's absolutely no way human input could improve on the system - even if it were possible to activate individual brakes.
The best driver in the world will be caught out by the unexpected, it's insane to think it's a good idea to turn it off.
On that note, I'd read info on the Saab system that stated even when the ESP was manually turned off that it's only off when not braking. Under braking the system will always be on. It was in my US Owner Manual pdf so not sure if that's US spec only?

"The ESP is always operative during brak- ing, even if it has been switched off manu- ally."

[Audax]

"The ESP is always operative during brak- ing, even if it has been switched off manu- ally."

I don't know, maybe it means you can't turn off the ABS function?

[fka]

Looked it up on WIS and it sounds like ESP will function if you are braking.

[Audax]

If you read between the lines it implies that but doesn't state it, it just says that the ESP system will regulate braking, that could simply mean you get an ABS function provided by the ESP system. There is no other system to provide ABS functions. However there is no way of determining if it means you get ESP or ABS or something else.