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 Post subject: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 02:03 
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This just happened...

Driving back from a friend's in Calne. Coming back along the lanes, tight left hand bend (normally a 35mph corner in clear dry conditions).

Approach speed: 15mph, maybe less.
Time: 12:10am.
Outside temperature: -2.5C

Hit a patch of black ice. Right on the bend. Was taking it easy - but managed to get into a 4-wheel drift for about a quarter of a second. Back starts to slide, I flick on some opposite lock. By this time the ESP has kicked in and sorted the problem out as I straighten up out of the slide.

All back on track in under half a second. Slightly hair-raising but not even approaching a brown trouser moment.

Now while I'm fairly confident that I could have pulled out of that slide in a car without ESP it would have been hard work. And a run-of-the-mill driver probably would have ended up in the hedge.

All new cars should have ESP fitted as standard. Not just the expensive ones like Audi or Mercedes. Not just the higher models with the more powerful engines. Everything, from a 1 litre Fiesta upwards.

Ok, so it needs ABS for the sensors etc... but ABS is also a good thing as it means that Mr Average can do a full-on emergency stop rather than having to master cadence braking.

Wasn't sure which part of the forum to put this posting in. It wasn't even a near miss, more an "isn't technology great" posting. Mods - feel free to move this if it would be more appropriate somewhere else?

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 02:38 
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Surely if the ESP had done its job properly, the car would not have broken away at the back, but would have allowed the front to go too and kept you nominally pointing in the right direction?

An average driver may have struggled without the assistance, but a good driver would have been going slower I think at -2.5° on a corner where black ice might lurk. I cannot recall when I last needed to correct for lost traction apart from occasions when I have deliberately provoked things to test a car's response to different stimuli.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 08:16 
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Squirrel wrote:
All new cars should have ESP fitted as standard. Not just the expensive ones like Audi or Mercedes. Not just the higher models with the more powerful engines. Everything, from a 1 litre Fiesta upwards.

Ok, so it needs ABS for the sensors etc... but ABS is also a good thing as it means that Mr Average can do a full-on emergency stop rather than having to master cadence braking.


ABS is pretty much standard fit, I think it was going to be legislated for but the EU manufacturers negogiated a gentlemans agreement.

The extra cost of an ESP system is additional yaw rate/lat acc sensor, additional valves (and hence larger/heavier valve block) and possibly an higher rated pump.


I'm inclined to agree that if ESP has kicked in you've already done something wrong, but thats an easy thing to say sat here.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 11:26 
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Squirrel wrote:
Ok, so it needs ABS for the sensors etc... but ABS is also a good thing as it means that Mr Average can do a full-on emergency stop rather than having to master cadence braking.



err, might be wrong, but I don't think that ABS helps to reduce your stopping distance, it just allows you to steer with your foot hard on the brakes. If I was buying new and all the electrical passive safety features were options I would leave all the boxes blank. Go too fast into a corner and you will still inspect the scenery, no matter the gadgets


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 11:49 
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err, might be wrong, but I don't think that ABS helps to reduce your stopping distance, it just allows you to steer with your foot hard on the brakes. If I was buying new and all the electrical passive safety features were options I would leave all the boxes blank. Go too fast into a corner and you will still inspect the scenery, no matter the gadgets
I wouldn't! Despite my abject comments above, I think the ESP (or VSA or whatever other euphemisms/acronyms different manufacturers use) are wonderful features. It's almost like having a limited slip diff but only when necessary.

You're right about ABS not reducing stopping distance over and above what, eg, The Stig could do with cadence braking or other techniques. However, on balance I'd have that too these days for simplicity (and madam when she takes the wheel).


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 13:24 
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Personally I don't like ABS and presently drive two cars without it. It's a bit of a "thing" I have against ABS. I've never tried an ESP car so wouldn't know how good it is but the fact that it involves having ABS would put me off it slightly.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 14:47 
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ed_m wrote:
I'm inclined to agree that if ESP has kicked in you've already done something wrong, but thats an easy thing to say sat here.


It's very easy to say that after the event too. You have the luxury of time - something that's missing when you're a bit tired (see the timestamp of my original post), been driving all day... and the temperature has suddenly dropped.

So if you can take bend x at 35mph in "normal" conditions with at least a 100% safety margin (it's a bend that if I used the full width of the road I could probably make at 65-70mph in the dry - I wouldn't do this of course, it's purely theoretical!) then 15mph tops in adverse conditions would seem logical. (It's an NSL road.)

The other point about ESP, particularly on a car with a sophisticated AWD system such as mine - you get little or no warning before the car breaks the performance envelope, unlike with a FWD or RWD car. As I found out on a skid pan. Turn the ESP off and once you break grip that's it, you've had it. By the time you feel the under/oversteer starting it's too late - and with AWD you're going so fast to cause this loss of grip that you've got no time to correct it - you're going to end up in the sand trap. (Or if you're on a public road... the hedge.)

Whereas when the ESP's on you've got that little bit of extra warning. When the light starts blinking when you took that last bend a bit on the quick side... that's telling you to ease off.

(Disclaimer - not that I'd advocate that sort of driving on a public road! Again, purely theoretical, or on a skid pan or test track.)

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Personally I don't like ABS and presently drive two cars without it. It's a bit of a "thing" I have against ABS. I've never tried an ESP car so wouldn't know how good it is but the fact that it involves having ABS would put me off it slightly.


Every car I've had except my first one after passing my test (1995 1.1 Fiesta!) has had ABS. The last 3 cars have had ESP. The last two have had AWD.

The only difference ABS should make to the way you drive is that in an emergency you plant your foot on the brakes and keep it there. No need to release the pedal to steer. No need for cadence braking.

It takes a cool head to cadence brake when an emergency is unfolding in front of you. I remember many years ago when I was driving my 1.1 Fiesta, coming off the M25 onto the M23 I'm confronted by some cock (actually driving an Audi A4 as it happens) reversing up the hard shoulder across the hatched area onto the slip road. I'd only been driving about 6 months at the time so hadn't yet learnt the observation skills to avoid getting into the situation in the first place, however a combination of cadence braking and the guy to my left seeing what was happening and dropping back to give me an escape route avoided a potentially nasty accident.

In my current car (2006 A4 Quattro) it would have just been a case of standing on the brake pedal and letting the ABS do its thing. Although to be fair I'd have spotted the hazard far earlier now with 200,000 miles of driving under my belt (at the time it was 6 months since I'd passed my test, I'd probably racked up around 6,000 miles if that) and probably avoided the need to take such action entirely.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 15:27 
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The level at which ESP cuts in depends on the car and how it is programmed. On one of my cars, it is possible to spin the wheels (15% slip allowed) and slide the rear (a bit) before the ESP cuts in. Thus, it is not a "get out of jail free" card on slippery roads. It does, however, cut out gross abuse of the handling on a very powerful RWD car. If you feel brave you can switch it off. :o

My other car has much less leeway. ESP cuts in when very little slip is detected between the wheels (4WD) and ultimately the engine throttle is also feathered to restore grip and steering way.

Would I switch off ESP on the road? No. This is a track only option IMO.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 15:51 
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I'm led to believe the ESP on my car is adaptive, that is to say if you drive the car hard it backs off the threshold. It is possible to get a degree of tail-out without the ESP kicking in, the Torsen holds most of it before it gets to the electronic reins stage.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 17:40 
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Squirrel wrote:
The other point about ESP, particularly on a car with a sophisticated AWD system such as mine - you get little or no warning before the car breaks the performance envelope, unlike with a FWD or RWD car. As I found out on a skid pan. Turn the ESP off and once you break grip that's it, you've had it. By the time you feel the under/oversteer starting it's too late - and with AWD you're going so fast to cause this loss of grip that you've got no time to correct it - you're going to end up in the sand trap. (Or if you're on a public road... the hedge.)


That may be a characteristic of the AWD on your Audi, but it certainly is not on an Impreza, though of course the AWD is not exactly sophisticated on a Scooby. It might also be down to very low grip conditions as I have really only practised this sort of thing on tarmac at higher speeds. There is sufficient feel/feedback to keep my car balanced where the car is right at the limit of grip on say a 70mph entry bend. Alternatively the bend can be taken at 85mph by deliberately pushing the rear wide then holding a slide through the bend, this sheds so much speed you can still make the exit without running wide. Both done with steering inputs alone, no brakes or accelerator allowed on this exercise. It takes a bit of practice of course and the instructor could easily add another 5mph. :D

A friend with an older S4 has also had a go at this, though the stability system cannot be entirely switched off so it would not allow a drift to be held.

I understand Honda S2000s become very difficult to control on the limit, so what I saying is not that you are wrong about your car, but that I do not think it is a consequence of AWD specifically.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 17:56 
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In the 6 years 8 months I've had my current car (no ABS or other nonsense) I have done 1 emergency stop, well didn't need to come to a stop. Had I been concentrating I wouldn't have needed to do that. The electric "safety" features are reactive and do not anticipate muppetry. I couldn't be doing with those "features" where if you get too close or stray out of lane all hell breaks loose. I'm the driver and I will take the responsibility for the drive. It must surely be better to drive observing the conditions.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 18:06 
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It has just come to me.

A week or two ago we had a pretty good frost here, it was forecast, but for what ever reason the roads didn't get gritted/salted. On the way out of the village (30 limit) is a mini round about and just the other side of that is a car in the (freshly cleaned out) ditch. The way it was pointed suggested it had come off the mini roundabout, so can't have been going fast at all. But is was an Auris which must surely come with all the latest and greatest gadgets to stop that sort of caper.

There was a traffic car blocking the road and I only wanted go a 1/4 mile so was going to go past it as no one was being shovelled up off the road. Copper rolls down his window, "it's VERY slippey, be VERY careful" "thank you officer, I'll be fine". I don't pretend to be Valentino Rossi, but I managed to get to work that morn on my scooter with out falling off, where a modern car driver failed.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 18:33 
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toltec wrote:
A friend with an older S4 has also had a go at this, though the stability system cannot be entirely switched off so it would not allow a drift to be held.

I understand Honda S2000s become very difficult to control on the limit, so what I saying is not that you are wrong about your car, but that I do not think it is a consequence of AWD specifically.

I used to have an S4 and the main issue with that was the nose heavy understeer. A 4 wheel drift was almost impossible!

The S2000 is VERY skittish on the limit and only the very latest models (last 12 months?) have ESP. The very peaky delivery of power also makes it tricky in slippery conditions.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 20:42 
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adam.L wrote:
Squirrel wrote:
Ok, so it needs ABS for the sensors etc... but ABS is also a good thing as it means that Mr Average can do a full-on emergency stop rather than having to master cadence braking.



err, might be wrong, but I don't think that ABS helps to reduce your stopping distance, it just allows you to steer with your foot hard on the brakes. If I was buying new and all the electrical passive safety features were options I would leave all the boxes blank. Go too fast into a corner and you will still inspect the scenery, no matter the gadgets


But what about adaptive braking, which sends the peak level of brake pressure each wheel? could stiggy brake faster than that? My van has that, as well as so many other traction/stability acronyms it needs a computer to organise them all. :lol:

apparently the acronyms are so clever they take throttle & wheel position in consideration when cornering loss of stability occurs to work out when you mean to go, how much this extends the "envolope" I don't know.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 22:13 
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hairyben wrote:
adam.L wrote:
Squirrel wrote:
Ok, so it needs ABS for the sensors etc... but ABS is also a good thing as it means that Mr Average can do a full-on emergency stop rather than having to master cadence braking.



err, might be wrong, but I don't think that ABS helps to reduce your stopping distance, it just allows you to steer with your foot hard on the brakes. If I was buying new and all the electrical passive safety features were options I would leave all the boxes blank. Go too fast into a corner and you will still inspect the scenery, no matter the gadgets


But what about adaptive braking, which sends the peak level of brake pressure each wheel? could stiggy brake faster than that? My van has that, as well as so many other traction/stability acronyms it needs a computer to organise them all. :lol:

apparently the acronyms are so clever they take throttle & wheel position in consideration when cornering loss of stability occurs to work out when you mean to go, how much this extends the "envolope" I don't know.



If you are driving on the ragged edge and trying to shave 0.1 second off a lap time then great, but I can't imagine a copper on the scene when I am being pulled out of a hedge telling me I should have a load of electrical guff, he'll probably say I should have been driving better. Maybe I'm wrong.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 22:48 
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malcolmw wrote:
The S2000 is VERY skittish on the limit and only the very latest models (last 12 months?) have ESP. The very peaky delivery of power also makes it tricky in slippery conditions.


all this talk of breaking away and how much warning you get sounds to me like how the car is set up.. if its set up to handle neutrally (i.e. sporty) you'll reach the limits of adhesion on both axles at pretty much the same time by which point there's not too much you can do about it, also slight variations mean one time it might oversteer another understeer, or slip between the two.

by pervceived wisdom most cars are setup to understeer, giving some warning, from steering feel or yaw response..... or some assistance from ESP if fitted.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Tue Dec 30, 2008 22:53 
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hairyben wrote:
But what about adaptive braking,


this is a merc right ?

hairyben wrote:
which sends the peak level of brake pressure each wheel?


kind of like ABS does ?

hairyben wrote:
apparently the acronyms are so clever they take throttle & wheel position in consideration when cornering loss of stability occurs to work out when you mean to go,


sounds like ESP ?

hairyben wrote:
how much this extends the "envolope" I don't know.


in principle, if you use it, ESP should extend the region where the vehicle behaves linearly/predictably.. the downside being when it's done all it can you're even deeper in the doo doo than you would have been.

that said most drivers rarely activate ABS, let alone ESP.


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 Post subject: Re: ESP - a lifesaver?
PostPosted: Wed Dec 31, 2008 01:54 
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ed_m wrote:
[
kind of like ABS does ?



I thought abs pulsated the brake pressure to prevent wheel lock and what I'm talking about adjusts individual brake pressure according to weight and load shift?

I may be wrong, TBH I just read the blurb and though "that all sounds jolly clever" and was somewhat amused that all the acronyms need overall management to prevent conflict. wasn't so long ago that ABS was bit posh.

ed_m wrote:
in principle, if you use it, ESP should extend the region where the vehicle behaves linearly/predictably.. the downside being when it's done all it can you're even deeper in the doo doo than you would have been.

that said most drivers rarely activate ABS, let alone ESP.


Thats what I was fumbling for, so long as it lets you know you're one step from OMG, presumably there's a warning that it's doing something? The only such warning my vans given me is when the TC decides to practically switch the engine off on a couple of occasions I've gone to boot it from a junction inducing slight wheelslip. And yes it's a merc with their famous paranoid traction control.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Wed Dec 31, 2008 10:27 
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I used to drive Merc Sprinters about 6 years ago. They were the most "tail happy" vehicle I have ever driven. Even fully laden the back would always try and overtake the front.

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 Post subject: Re: ESP - a lifesaver?
PostPosted: Wed Dec 31, 2008 13:11 
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ed_m wrote:
you'll reach the limits of adhesion on both axles at pretty much the same time by which point there's not too much you can do about it


It is not really a binary situation, agreed you can find yourself with little or no grip, however the progression to that point is a continuum of increasing slip angle. The rate of change may be very high when caused by black ice etc. or it appears going beyond the limit of an esp system may well leave you with no control. In less severe situations however, even in a four wheel drift, you can exercise a surprising amount of control with steering input alone, the addition of braking and throttle inputs to promote weight transfer add extra options.

This of course is not easy and takes quite a bit of practice, I rate my skills as only a little above novice in this respect.

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