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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > DSC just kicked in, Yo...



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      05-19-2011, 01:18 AM   #67
SteveC
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Sliding a car

With the 330d, 335i, 335d and a host of other models, BMW are providing the public with cars that have extremely high limits of power and grip but likewise the capacity to overstep those limits by huge margins.

The main 'problem' facing BMW in producing a car that is both safe and fun to drive is that the main variable in terms of safety limits is available grip, which can vary hugely according to many factors including:
  • Road surface type
  • Wet or dry conditions
  • Road surface contamination
  • Road surface condition (smooth, uneven, bumpy etc.)

Not only can road surfaces vary, they can vary within inches such that the car may suddenly go from high grip to very low grip (fuel contamination for example), or may suddenly encounter different levels of traction between left and right wheels (puddles, manhole covers etc).

When a driver knows the road surface intimately, as would possibly be the case on a race track, he/she can use skill and experience to maintain control of the car without the need for traction control

In all other circumstances the driver has no clue about the condition of the road surface. It may be contamination, subsidence, a slippy manhole cover, new tarmac that's oozing heavy hydrocarbons, whatever.

The point is, that when the car is on the limit of grip at high speed in perfect conditions, no driver has the reaction time to correct when those conditions suddenly change. Electronics do

Go round a roundabout close to the tyres' limit of grip without DTC, suddenly encounter a low grip surface and the chances are very high indeed that you'll lose the car. Watch F1 drivers on slicks in the wet for a graphic demonstration of what I'm talking about.

Switch off the safety devices on a dry track and a skilled driver will generally circulate faster. Do the same on a wet track and and that's no longer the case. The reason is because of reaction time and sensitivity. What is happening is either the driver keeps the car well below its limits or momentarily loses control of the car, before reducing the load on the tyres with opposite lock. The electronic safety devices allow a driver to keep the car at but not beyond its limits, which is obviously faster (F1 with traction control was faster than without).

So its not lack of skill that causes problems of driving without safety controls engaged; rather its lack of sensitivity, reaction time and the millisecond by millisecond knowledge about what's happening with grip levels under all 4 wheels that causes problems.

At a roundabout near my home. its a regular occurance for cars to leave the road in damp conditions. In my 330d, on the same roundabout you'll see a little yellow dashboard light flash momentarily
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      05-19-2011, 03:17 AM   #68
chrismanchr
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as good as the dtc/dsc is ,too much power ,with speed then sudden and totall loss of grip on say 1 wheel (grid cover) and it will go ,it has its limits ,but i agree it is a good system and ive been watching the dtc the last few days keeping this thread in mind ,and i had it engage a few times but all low speed slides ,I think its a lot less harsh than on the old e46 ,maybe thats down to the vehicle setup ,because turned off its not as tail happy as the old models,
I think i need new tyres now lol
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      05-19-2011, 08:34 PM   #69
Sandwich_Dan
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Quote:
Originally Posted by SteveC View Post
With the 330d, 335i, 335d and a host of other models, BMW are providing the public with cars that have extremely high limits of power and grip but likewise the capacity to overstep those limits by huge margins.
My old MX-5 on it's original fit Bridgestone ER30s with nothing more than ABS and a chassis setup to hardly ever understeer gave me a lot of respect for handling a RWD car. However, modest grip and 146bhp meant that I was happy to play alot of the time - it was rare for a day to pass wthout a dab of oppo.

When I moved to the RX-8 both the grip and power went up. Places where I used to play suddenly seemed a bit dodgy because of the extra speed required. It was fitted with a pretty violent stability control system (it just fired the ABS at full pelt on whichever wheel it felt necessary) so I would occassionaly switch it off but with the slippy diff, peaky power delivery and stiff suspension it was a hell of a lot harder (and more risky) to play with than the Top Gear reviews would lead you to believe.

In the 335i I just leave everything switched on, but I aim to never see the flashing orange light even when having fun. To me, especially after the MX-5 - probably the most fun car the average driver could own - the 3 isn't a car to hoon around in. Just leave the DTC button alone and let it gather up the moments you don't see coming.

Or maybe I'm just getting old.

Last edited by Sandwich_Dan; 05-19-2011 at 08:43 PM.
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