http://uk.youtube.com/watch?v=1zX5dQkb-xQ
THE ALL SINGING AND DANCING BMW E31 850
WHAT A MOVER

can you say worn bushings?how can they possibly get that bad?:help

cobra, you aren't serious.......

Incidentally, I was reading the tech details of the new 7 series. It has an updated version of the AHK system. This time, both axles can turn both in sync (high speed maneuverability) and in opposite directions (low speed maneuverability).

cobra, you aren't serious.......

:)lol
gotta love the euro-csi

cobra, you aren't serious.......yea i was serious!.i had no idea these cars incorporated all wheel steering.you gotta give me credit for stepping up and calling myself an idiot!:lol

yea i was serious!.i had no idea these cars incorporated all wheel steering.you gotta give me credit for stepping up and calling myself an idiot!:lol

Indeed.....:thumbup:

I new that would catch someone out.
the wife thinks bmw have taught an 8 to dance.
I took my ci to the local main steelers, They hadn't seen one either.
In the repair bay they pluged it into the computer and made it dance, wish I had a camera with me to record that.

I'm curious how well that system holds up and what maintenance it needs. If it's anything like EDC shocks the cost has gotta be to the moon....... do you like it?

I don't know about the technical isues. but to the best of my knowlege ahk comes in to play as a counter measure against overstear.
bmw's master technition tells me (to see this function at work you will have to follow the car through a corner at high speed) A symbol lights up in the dash when ahk is deployed it looks like the 4 w steer symbol on a allterain wheeled excavator. it dose not opperate for changing lanes.
I'm sure some one with more knowledge will make coment
I wonder if ahk is a + or a - for drifting!

While driving in a straight line without accelerating or decelerating the weight of a car is static with the center of gravity somewhere in the middle of the car. But when turning-in the weight still wants to continue its straight line. The center of gravity is pulled away from its original position. This is called a weight transfer. Depending on many factors such as grip, speed, angle of turn-in,... the weight transfer can cause instability like oversteer. It should be clear that the less sudden the weight transfer occurs, the less chance there is on instability.

With a passive steering rear axle the forces generated by a sudden weight transfer while steering-in make the rear wheels turn a little in the same direction as the front wheels - towards the inside of the corner. This makes the center of gravity move less fast away from its rest position, thus increasing the car's stability. AHK works very similar, but being an active system it will turn the rear wheels even before these forces have built up. In other words, it reacts a lot quicker on sudden weight transfers. Furthermore it allows the rear wheels to steer to a greater extent, allowing an even greater degree of correction.

It doesn't matter whether you are just taking a bend or changing lanes. If the conditions apply, AHK will engage and increase stability or perhaps even save the day. This gives AHK equipped cars a nimbleness you would not expect in this weight class. It's as if it weighs a lot less than it actually does. The 850CSi feels very nimble and stable during aggressive steering manoeuvres that would have many other cars lose control and crash. It's seemingly defying the laws of physics...

... which it obviously cannot. AHK will help to slow down the weight transfer, but it cannot make the "missing weight" disappear. Once in the curve the weight transfer will stabilize, but the center of gravity is still away from its rest position and pulling on the car with full mass. If it's pulling beyond the grip levels, you lose control. So AHK will help on turn-ins, but it will not make the car go any faster around corners. The E31 is still a heavy car which will never go around corners as quickly as a lighter car.

Is drifting impossible? No, certainly not. But obviously it requires a bit more effort to get the car into oversteer due to AHK. Just flick it in a bit more aggressive, more power,... Once you push beyond the limits of AHK, the car will drift very much like any other car with similar specs.

http://www.youtube.com/watch?v=uXeylU662sw

Starting at 1:15 you'll see the driver engaging in a few drifts. Obviously no show drifting, but it clearly shows the 850CSi has no problem with being controlled in oversteer.

there ye go.I could have told ye that.
99 ci's were equiped with ahk in the uk mine is one of them.
thanks REVTOR very well done

I'm glad mine doesn't have it. Would just be one more thing to worry about LOL.

Yes, AHK is yet another item that can break down, but it's not particularly known to be an unreliable item on the E31.

The bad news is that when AHK fails it usually ends up being a very expensive repair and I've seens quotes of 10.000 euro to get it fixed (*). The good news for those low on cash is that when the system fails it goes in a sort of safe mode where the rear axle steering is locked in the center position. Obviously you lose the increased stability, but you can still drive the car normally without issues. I read about several people who drove around with a broken AHK for a long time.

*: Because AHK is so rare you'll find virtually no technician with knowledge of the system. Most have never seen it before. So instead of finding out what causes the issue, they rather replace the whole system what explains the hefty price tag...

8tech had a thread last week (posible csi for sale) i'm sure it was there yesterday.
the car was a friends, ahk was inop.
mine gave me a fright last year.
OBC........rear axel failed mode......££££££££
well it looked somthing like that. I limped home. I noticed oil covering the rear wheel.removed that, uncovered two pipes,(they were the same diamiter as brake pipes. found the corroded section and spliced a length back in. topped up the power steering reseviour and away I went.
all the £££££££££££££££££££££££££££ went out on the QBC happy days

I once saw a video where they compared standard 850 to CSi around the short slalom course. Video showed how much more agile CSi was around the corners. Does anyone have a link to that video?