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bobbycrispbox
Member Since: 15 May 2006
Location: Where women glow and men plunder
Posts: 2580
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| Traction control and the solid brake pedal |
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Before I start on this... I know that I hadn't waited for the path to be clear, and I know that I left braking until quite late. I'm not trying to divert blame here, I'm under no illusion as to where that lies.
The path goes through a deeply rutted, very muddy track, with a bit of a climb on the far side. It needs to be attacked with some momentum, and to that end I'm in Sand mode, with DSC off. I start in 2nd, work up to 5th in the mud, and back down to 3rd as I climb out the other side. As I'm coming out the other side, the traction control is still working extremely hard, to get the power down in the mud.
As I came up to the 'obstacle' I came off the accelerator, on to the brake, and found it to be absolutely solid, it would not budge at all. And for the next few moments I continue forward with quite some energy. There was a thump, and the game was over.
So folks, what are your thoughts. Why couldn't I press my brake pedal down?
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 19th Mar 2009 10:05 pm |
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Donald
Member Since: 15 May 2007
Location: Inverness
Posts: 188
  
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I suspect that DSC has kicked in automatically due to your driving style, despite you dis-engaging it. Sand mode is trying to hold revs and a high gear but you have manually changed up and down gears. DSC will have applied the brakes, you are still accelerating - your traction control working overtime to fight it comment, when you tried to brake the solid pedal was due to the brakes already being applied. Momentium and the laws of physics did the rest. Chipped, K&N, tow pack, AT2's, Mantec, fridge in boot, invertor, Garmin, laptop/Memory Map, Optima yellow top, Traxide Kit, Phillips Extreme bulbs
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| 19th Mar 2009 10:26 pm |
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bobbycrispbox
Member Since: 15 May 2006
Location: Where women glow and men plunder
Posts: 2580
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I don't think the DSC would have had cause to apply the brakes, as my progress was in a straight line. Only traction control would have been responsible for the braking, in my opinion.
But I agree with you that the brakes would have been applied hard as I progressed through the slippiest bit - there was a lot of power going to the wheels and not much grip so the brakes would have been working hard to keep the spin in check as much as possible.
But should the vehicle allow itself to get into the situation where the traction control is using 100% of the braking potential to control the slipping of the wheels? I would say no. I'd say that's why you can't completely turn off DSC.
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| 19th Mar 2009 10:42 pm |
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shopbobby
Member Since: 08 Mar 2008
Location: Herefordshire
Posts: 166
 
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Are you sure it wasnt a stainless steel coffee mug wedged behind the pedal:?:
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| 19th Mar 2009 10:51 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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DSL DSC does not apply the brakes, more likely that your vac pump is leaking engine oil into the servo reducing braking efficency, the test is to start the engine and fully depress the brake pedal until the servo assistance is lost, if this is <10 presses then the vac pump is suspect - open the servo vac pipe connector to check for engine oil in the pipe
BTW, vac pumps are on backorder 
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| 19th Mar 2009 11:03 pm |
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GLYNNE
Member Since: 06 Oct 2006
Location: KENT
Posts: 4645
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He just didn't want me to win  and couldn't handle the fact i was in front 
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| 19th Mar 2009 11:09 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
 
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Iain, I thought DSC used braking on individual wheels and a reduction in engine power to help reign in a slide ?
Certainly what I've seen on the tarmac when its kicked in.
Not it BCB's case mind... but generally as a system.
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| 19th Mar 2009 11:10 pm |
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Donald
Member Since: 15 May 2007
Location: Inverness
Posts: 188
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TFC if he was losing servo assist would he not have noticed before or after as well?
Simon,DSC does as you say. When you manually swith it off you only switch off the power reduction not the brake application. Chipped, K&N, tow pack, AT2's, Mantec, fridge in boot, invertor, Garmin, laptop/Memory Map, Optima yellow top, Traxide Kit, Phillips Extreme bulbs
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| 19th Mar 2009 11:21 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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simon wrote:Iain, I thought DSC used braking on individual wheels and a reduction in engine power to help reign in a slide ?
Certainly what I've seen on the tarmac when its kicked in.
Not it BCB's case mind... but generally as a system.
DSC doesn't apply the brakes, ABS does... DSC backs off the throttle, stiffens up the suspension on the 'outside edge' if in a corner and increases braking effect on the 'inside edge' IF the brakes are applied manually, the brakes are not applied if no brake pedal input is detected
What you are feeling is engine braking using the throttle butterfly to increase the effect - food for thought if you've gone down the EGR blanking process 
If you want to prove / disprove this, get someone to follow you and see if the brake lights come on... brake lights will come on with any automated or manual braking effect, HDC, TC, EBD or ABS
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| 19th Mar 2009 11:28 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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So if you induce a slide (on tarmac) the brakes are not used at all to help reign you in ?
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| 19th Mar 2009 11:33 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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This is what LR say...
Quote:These systems work with the braking system to correct cornering (over or understeer) and to help maintain stability at all times.
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| 19th Mar 2009 11:36 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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Only if you press the brake pedal, then braking assistance is invoked through EBD or TC or DSC dependent upon yaw rate, steering angle, accelerator pedal change-of-position rate, suspension pressures and a few other inputs
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| 19th Mar 2009 11:36 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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So does DSC engage and control the ABS system ??
If so - to me DCS applies the brakes 
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| 19th Mar 2009 11:37 pm |
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10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
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It depends upon the sensor input, braking is not automatically applied in every situation where DSC is invoked but can be applied to supplement DSC - not as a default DSC strategy
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| 19th Mar 2009 11:39 pm |
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simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
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Ah... so the brakes are applied by DSC in certain situations then if the system deems it necessary.
Hair splitting (to me as a luddite) then
DSC (as LR state - and yourself) works with ABS, suspension and engine management systems.
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| 19th Mar 2009 11:47 pm |
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