Very close call!

2.7 V6 30v biturbo - 380 bhp
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FrankC
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Very close call!

Post by FrankC » Thu Jan 13, 2005 12:49 am

On my way home tonight,i noticed that the temp display was showing 2*c so i backed off the throttle to around 60mph.
As i started my turn into a left bend,the back end of the car suddenly let go resulting in the car going almost sideways up the luckily deserted country road.
I tried to correct the car using only the steering wheel and after about 4 or 5 secs i managed to bring the car back under control.
During the time the car was snakeing from left to right i managed to glance and noticed that the esp indicator remained off!

I thought the ESP would have jumped into life braking the relevent wheel or wheels,but it really felt like i was having to do all the work after hitting a long stretch of black ice?

After i had proper control over the car i applied the brakes as hard as i could and the car went into a slid,i felt the ABS kick in but again no ESP light flashed.

Is this normal,as i must confess this is the first time my arse has gone proper in the car???
Cheers fc

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kiwi_mtm
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Post by kiwi_mtm » Thu Jan 13, 2005 6:02 am

sounds very odd.

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Post by kennyboy » Thu Jan 13, 2005 9:26 am

If you were not accelerating by means of applying the go faster pedal then I don't think the ESP would kick in.

The only time I felt the ESP kick in was going fast round a bend with me having me foot down on the gas. Dectecting slip, the ESP light came, notice the weird sensation someone else braking for me (with me still on the gas)- which I lifted off and thought what the....

Therefore I think it would only kick in by braking when your trying to accelerate on purpose, as I have described above.

Only other time is accelerating straight, hit a pot hole; that particualr trye had no contact with the ground and the ESP light came on.

I assume while you were snaking, you lifted off the gas (1st natural thing to do?) so the ESP can't brake/ help you out as this point in time for you.
Last edited by kennyboy on Thu Jan 13, 2005 9:35 am, edited 2 times in total.
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simple1
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Post by simple1 » Thu Jan 13, 2005 9:30 am

Not so odd, The ESP will usually only light up when under power, you were for all intensive purposes, free wheeling if you did not apply throttle or brakes. When you did apply the brakes the ABS would do its stuff, but the ESP would still be doing nothing, had you applied full throttle once the car was under control, it would have lit up if it detected wheel spin....

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Post by Vortex » Thu Jan 13, 2005 9:42 am

Generally Traction Control works via the wheel speed sensors for the ABS, and only acts to conteract slip. The majority work via a soft ignition or fuel cut. So yes they will generally only work under power, I have no working knowledge of the Audi ESP though.
Last edited by Vortex on Thu Jan 13, 2005 9:47 am, edited 1 time in total.

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Post by Vortex » Thu Jan 13, 2005 9:45 am

Has anyone tried the RaceLogic traction control on an RS4? They are in cabin adjustable( you dial in the percentage of slip you want), and have launch control. They are an exception piece of kit.

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RS4ge
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Post by RS4ge » Thu Jan 13, 2005 9:58 am

kennyboy wrote:The only time I felt the ESP kick in was going fast round a bend with me having me foot down on the gas. Dectecting slip, the ESP light came, notice the weird sensation someone else braking for me (with me still on the gas)- which I lifted off and thought what the....
My ESP seems to kick in almost every time I overtake in 2nd or 3rd. I guess it could be partly due to the greasy Peak District roads and partly that the straights are short (so you've got to go for it quickly) but does anyone else have this regularly - or am I just too heavy on the gas???

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FrankC
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Post by FrankC » Thu Jan 13, 2005 10:29 am

Kenny,i did take my foot off all the pedals once the car was out of my control as i felt like the right thing at the time to do.

RS4ge i often manage to light the ESP indicator during overtaking in almost all the gears,usually on the type of road conditions you describe.

Just checked the roads about half hour ago,black ice everywhere :shock:
Cheers fc

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Diesel
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Post by Diesel » Thu Jan 13, 2005 11:29 am

I have had ESP come in twice now (with associated wheel braking). Once was under power whjere it was understeering too much due to the negative camber (by Tescos' there Ken!) and it braked the rear offside to swing car round. The other time was yesterday when i was flat out in second 'straightening' a roundabout but there was a dip in the road and I guess tyres left the ground. Bloody heartstopping both of them as it's like the unexpected hand of God when the wheels chirp!!!
AMD III RS4

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Post by DavidT » Thu Jan 13, 2005 11:48 am

ESP will engage even if you have the car in neutral if it detects significant understeer or oversteer, i.e. loss of grip front or rear.

It is less interested in four wheel drifts (equal loss of grip at both ends). Shame it's so difficult to get the Audi's to drift.

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Post by Vortex » Thu Jan 13, 2005 12:04 pm

How does it work then? Is there a tech write up somewhere?

Also, can it not be reprogrammed?

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Post by DavidT » Thu Jan 13, 2005 12:13 pm

Dunno about a write up, but it works by taking inputs from things like steering angle, throttle and brake position etc and combines it with longitudinal and lateral acceleration measurements (sensor for this is under one of the front seats). From these, it decides if the car is sliding too much and takes control of throttle and individual wheel braking to attempt to get the car to do what the drivers phyiscal inputs are requesting.

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Post by don » Thu Jan 13, 2005 12:16 pm

My understanding is that ESP will kick in during loss of traction under accelleration and during excessive yaw.

I assume in the case of black ice there is no excessive yaw due to a 'frictionless' slide, so the ESP probably doesn't know any better.

In such cases I'd be braking as hard as I can, atleast that way the ABS and EBD can do their work.

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Post by DavidT » Thu Jan 13, 2005 1:05 pm

Traction control = wheelspin prevention

ESP = Stability (slide) management. The system will always know when the car is slided because it is measuring longitudinal and lateral acceleration and combining them with other inputs then comparing with stored maps.

Example:

Car is doing 30 mph, half turn of left lock, and 0.0g of lateral acceleration i.e. going straight on. The car is sliding. This is very simplistic but it illustrates how the system works.

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Post by Carps » Thu Jan 13, 2005 1:13 pm

ABS doesn't work so good on significant amounts of ice. I have had times when slamming on the anchors results in all four wheels locking quickly enough for the ABS system to just think I am stopped - ie, no differences between wheel speeds. The result is a locked up car sliding merrily on its way. I have had this in VW and Audi cars, and it takes you by surprise first time as you kind of assume that ABS will save the day when in fact it makes it worse (if you are conditioned to leaving your foot on the brake as per ABS instructions)

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