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Acceleration Lag

Printed From: Bavarian-Board.co.uk - BMW Owners Discussion Forum
Category: Technical & Model Specific Forums
Forum Name: BMW 8 Series
Forum Discription: This forum will deal with any issues on the E31 BMW 8 Series
URL: http://www.bavarian-board.co.uk/forum_posts.asp?TID=8911
Printed Date: 03-May-2024 at 03:27


Topic: Acceleration Lag
Posted By: Angus
Subject: Acceleration Lag
Date Posted: 06-July-2004 at 22:15
I have an 1999 840 Ci Sport.  Just getting used to it and notice that if I put my foot flat to the floor to accelerate fast, there is a distinctive lag, as if the engine is not responding, then it surges forward.  I found this disconcerting, expecting the car to respond instantly - has anyone else found this?  Is this normal?  I thought maybe it was the ASC preventing rear-wheel spin.  If I switch ASC off, then it is more immediate in response, but still a slight lag.

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2 x E32 + E31 = much pleasure


Replies:
Posted By: aussie840
Date Posted: 15-July-2004 at 13:08

Hi Angus,  thats no good, should be instant response.  I think you might need to get your 8 hooked up to a DIS diagnostic unit a dealer.  Could be the fly by wire throttle control module playing up or the traction control unit is kicking in and retarding the fuel, this can be caused by difference in rotational speed between rear wheels, but you say your getting lag with it disabled.

If you keep it 2nd gear and get on & off the throttle betn. 3000 & 7000rpm does it still hesitate?

Ian

Posted By: Angus
Date Posted: 26-July-2004 at 17:34
I did as you suggest and it is responsive in manual mode.  The delay is very apparent when using kickdown in automatic.  Accelerating hard but without actually kicking down is responsive so guess there is a problem on the kickdown system.

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2 x E32 + E31 = much pleasure

Posted By: aussie840
Date Posted: 28-July-2004 at 08:52

Any difference between E & S modes on the transmission during kickdown?

Ian

Posted By: Angus
Date Posted: 11-August-2004 at 19:43

Hi Aussie,

There is no E or S mode.  The only option is switchable between automatic or tiptronic manual.  Only other options are Sports or Komfort suspension.  The original sales brochure says:

"the gearbox has Adaptive Gearbox System (AGS), it determines the optimum gear in each situation.  It gives you the choice of four driving programs ranging from particularly economic all the way to very sporting.  To recognise the driver's style of motoring, AGS constantly monitors the position and operation of the accelerator.  Then it compares wheel slip and drive forces, adjusting gearshifts to road conditions categorised as "normal", "winter" and "mountains/starting off".  Finally to add the ultimate touch, AGS takes each specific driving situation into account and avoids unnecessary gearshifts - for example in stop/go traffic or in bends.  The result is not only extra comfort, but also extra safety on the road"

I guess they don't figure a program for the speed hungry maniac!

 



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2 x E32 + E31 = much pleasure

Posted By: agremlin
Date Posted: 13-August-2004 at 23:15

My 840 Ci Sport does the same thing if you boot the throttle from a standing start in Sport/Drive (Tiptronic) - it just goes gulp, sticks its nose in the ground and goes nowhere.  If you flick to M1 then it goes off the line just fine. 

I don't have any problem with kickdown - it just boots you in the spine.  It is possible that the delay you describe could be down to a tired/broken torque convertor (expensive).  If you can get at it, then take a look at the transmission fluid and see if it is showing signs of being burnt.


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