Roger wrote:
Mole wrote:
You can still get pedal kick-back with ESC - it still uses the ABS pump to lock / unlock whatever wheel is appropriate to what it's trying to achieve.
Unless they have got very sophisticated of late, the ESC applies brake forces to wheels that are losing drive (on the driven axis) and to an imperceptible extent to cause weight redistribution or (very momentary) loss of traction on the wheel(s) on the passive axis. By definition, when the ESC lets go, unless you have the brake pedal planted, it will let go of the wheel(s) it had braked and allow it/them to spin freely again.
Pretty certain it can do more than that on most modern cars. It certainly does what you suggest, but I think it will also brake a wheel on the non-driven axle if it wants to degrade the grip at that end instead. Part of the problem is that there isn't a standard for many of these "whistles and bells" as yet, so each manufacturer does their own thing and has their own terminology. I know there's a lot of regulatory work going on right now to try and develop standards / regulations for these systems.
Roger wrote:
Mole wrote:
The first time I took Mrs Mole's previous car (something a bit sportier!) out for a gratuitous hoon in the snow, I was surprised to hear the pump cut in when I pulled the handbrake on - without touching the brake pedal.
That would have been it trying to compensate for what you'd done. If this was in a rear drive car, if one of the rears had locked/semi-locked as a result of your handbrake tug, it would have thought that that was the one getting traction and applied brakes to the other one to even up the score. If it was a front drive car, it would have also removed/backed off the power as it would have thought that it was front wheel spin.
No it's smarter than that. It was a front wheel drive - an Alfa 156. It knew I had my foot on the throttle and that both front wheels were turning but that the rears had stopped. However, I'm pretty certain that it takes an input from the handbrake warning light switch too, so it knew the rear wheels had stopped because the handbrake was on, rather than the fronts were spinning and the car stationary. I think it also had a yaw sensor which told it that the vehicle was starting to spin. It then thwarted my efforts by shutting the throttle and braking the "outside" front wheel so as to straighten the car up (albeit at the expense of a short 4-wheel drift before it scrubbed off its speed and stopped).
Roger wrote:
Mole wrote:
It did a spectacularly good job of preventing me from enjoying a handbrake turn!
It should not have done that. Or was it a grey import? Vehicles approved for use on English roads must have an independent and un electronically-interfereable means for the emergency brake. It could have applied brakes to other wheels, but should under no circumstances have kicked you off the handbrake. The kick-back works the hydraulics - the handbrake should wither work on auxiliary pads/shoes (disk braked cars usually do this as it's easier, and often they are in board from the wheel on a stub axle), or, on drummed rears, a separate mechanical cam that applies the brakes irrespective of what the hydraulics are doing.
For "English" read "EC" these days! Yes, it was purely mechanical and no, nothing interfered with it. As you suggest, it had no means by which to do so - so it just messed about with the other end of the car to spoil my fun! The handbrake was still on as I came to a stop and didn't do anything peculiar. As stated above, I'm pretty certain it just braked the front wheel on the outside of the curve in which the car was travelling, to degrade its grip and straighten me up.
Roger wrote:
Mole wrote:
Fortunately, it still had a switch to turn the ESC off, but I really was quite impressed with how it prevented the car from oversteering when I had my foot on the throttle and was pulling the handbrake on whilst winding on an armful of lock!
I still do handbrake about faces in the snow when I'm facing the wrong way - for efficiency rather than effect. And I don't turn the ESC off.
Yeah, that's the thing. Everyone's magic system works slightly differently at present. To be honest, I like finding out about each new vehicle's little quirks, but I'm sure the regulators will kill that pleasure off in the next few years. The "General Safety Regulation" which comes into force (starting) in (I think) 2014 will demand that all passenger cars are fitted with ESC (among other things). Mrs. M's current X-Trail is another example. In the wide, snowy entrance to our lane, I've been sticking it in 4-wheel drive and booting it as I come round the bend. Sometimes, I can get a half-decent amount of oversteer before the little yellow "you're-having-too-much-fun" light starts flashing and it straightens me up. Other times I've actually bottled-out and lifted off because I've thought I was going to spin before it comes on! Not sure why, but it's quite unnerving. You start to trust it and about every fourth or fifth time, it lets you get well and truly out of line before cutting in. I'm assuming it's the "teach-you-a-lesson" algorithm in the software