 | Home > Puma (Tdci) > Ref old 2.2 post re switching traction control off |
 
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| Devon-Rover Member Since: 22 Jan 2015 Location: South Devon Posts: 918   
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If I imagine the situation like you describe it then the failure of the ETC system isn't your problem, lack of momentum was. ETC isn't a magic device and so it sounds like it was being worked hard to no effect hence the effect on the brakes.
ETC will help on say a steep climb where there are washout's enough to cross axle the vehicle providing there is grip enough for the transfer of power to be used. On steep muddy climbs then carrying good momentum will aid you far more than asking the ETC to vainly shift power to 4 wheels of equal non - existant grip. Save the pennines on fancy switches that To be honest if the ETC was turned off you still be stuck.. |
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15th Dec 2017 9:31am |
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| foggydave Member Since: 29 Nov 2012 Location: Midlands Posts: 263 
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Hi The post is on the link below
http://www.defender2.net/forum/topic27039-45.html (sorry but this link takes you to pase 4 of post) The discussion centered more on losing traction on hill climbs trying to power through it and because the wheels were spinning faster than the vehicle speed the traction control jammed the brakes on. The discussion was then hi jacked and discussed hill climbing techniques I caravan a lot and am often required to tow caravans out of muddy situations, which was in my old 2001 Td5 This was after my mates Disco sat spinning its wheels with traction control cutting in and out going now where. I now own a 2.2xs utility and dont want to be in the same situation. |
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15th Dec 2017 9:59am |
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| Devon-Rover Member Since: 22 Jan 2015 Location: South Devon Posts: 918
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I can see how the topic went off on a tangent and it again bears on what I said earlier
The system works on the premise that it wants to see equal wheel speed all round if there is a greater difference then it will brake (to a degree as the system will get more aggressive the greater the difference) the 'spinning' wheel to balance the speed. Now if all 4 wheels are on an equaly slippery surface then the system will just idly chunter away to keep all 4 wheels turning at the same pace. the result is still no forward progress and just lot's of pad wear and heat generated. This is where you go old school and use the apprepriate technique to cover the terrian and especially relevent in muddy / slippery scenarios is use of momentum to keep yourself on the move. On say very soft ground then you are looking at maintaining forward progress so low range 3 - 5 centre diff locked and keeping it moving using light throttle but still keeping the revs in the 2 - 4K range. What i'm doing is giving my self a good ground speed to 'float' over the bits that you would sink into if you stopped or would cause wheel spin and digging in when trying to get moving. as the ground is 'weak'.  Click image to enlarge For instance once when crossing a very wet fields I has keeping the speed (Low 3 - 4 CDLocked) and rev's high this gave me good momentum and when going up slopes I could build momentum and (using the ETC as a tell) I could accelerate until it chimed in then I would back off the throttle and feather it so keeping the engine speed matched to the ground speed thus maintaining traction. If the momentum isn't enough and you slow down enough all that happens is wheel spin will happen and you will no longer maintian forward progress. It is recognising this and accepting to either back out to have another run or if the slope isn't that great turing down hill to loop round for another run. Continuing to power up with ETC becoming more agitated trying to send power to 4 low grip wheels will just dig you in and come to a halt. Click image to enlarge Here we have 2 maybe more tons of trailier behind me. the ground was slippery but I wasn't sinking in so to use the correct terminology it is horizontally weak. In the film you will see i'm drive assist winching as there is no way it's driving out as all that happend was the ETC just sat there shuffling the wheels and I started digging down and a 3/4 wheel turn at a time. If I had the inital momentum to get going I reckon it would of driven out but the situation dictated I had to hitch up in the middle of the field. In a perfect world I would of had some Maxtraxx to layout to give you that inital momentum but alas I'm not that rich. We could of tandem pulled using a kinetic to get me moving but in light of not tearing up the ground I opted to winch as it was the most friendly way out. Now i don't think you are ever going to be at a site in that much mud but the best you can do is have good tyres dropped to a low pressure and maybe some means of traction assitance to just get moving and you and the van should be ok. Else wise you will like your friend just have 4 wheels spinning with the ETC trying to do it's job with as much success as attempting to put out a bonfire with a water pistol. Once going then enough speed to keep moving not too much so you have control and not being aggresive on the throttle to not break traction. |
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15th Dec 2017 11:18am |
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| foggydave Member Since: 29 Nov 2012 Location: Midlands Posts: 263
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Wow thanks for that. You put in a lot of work on that and very very informative.
With the wheels spinning would the ABS have any input as this may be what caused the brake problem ie locking the brakes on, and where a dab on the brake would take them off? The pictures look like Badminton show ground which is where my mate got stuck. |
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15th Dec 2017 4:58pm |
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| DSC-off Member Since: 16 Oct 2014 Location: North East Posts: 1433 
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Foggydave,
It sounds like you're concerned that the traction control may have caused your mates disco to get stuck, while your old Defender didn't, and you don't want the traction control getting your new Defender stuck? Was it a TD5 Discovery 2? if so, it probably didn't have a centre diff lock, and was totally reliant on traction control to keep it moving once any one of the wheels started to spin. So it was much more likely to get stuck in the first place. The 2.2 Defender has a centre diff lock, same as the TD5 Defender had, using it will get the defender a lot further before the traction control even starts to work. Use the diff lock then -when TC kicks in- your new defender will go even further than the old one did. Tyres will also play a big part in the difference seen between the Disco and Defender. The Defender tyres will probably be narrower, taller and more aggressive, giving better traction in mud. A TC equipped vehicle should perform better than a non TC if all else is equal. |
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15th Dec 2017 5:34pm |
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| Devon-Rover Member Since: 22 Jan 2015 Location: South Devon Posts: 918
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Foggy: having read the article The two stand out issues that I saw was the Apparent ability of the ETC when operating to completely stall the vehicle during an ascent. And the brakes becoming non functioning after hard ETC use as described as the pedal goes hard.
This is anecdotal and as not being present you cannot say for sure but summise on the evidence given. I'll just say that before I get leapt upon by the masses. Firstly I have seen large ETC action stall a TD5 on a failed ascent as the Antistall software isn't that advanced so as the revs die off the driver continues with a throttle action (this disable the antistall AFAIK) until it is too late then it stalls itself in a sudden lurch. The TDCI anti stall system is active regardless of throttle input AFAIk and I think it was JST who quoted that. I would find it hard to think that could happen. I have once worked the ETC very very hard being almost bogged to the diffs in moorland peat in a situation where I could only reverse three vehicle lengths before a rock was behind me and I completely mis read the ground. Having gone round the rock in 2nd low the landy promptly started to sink. After a few good rocking fore - aft attempts going from reverse to 3rd low in a not so friendly manner and employing a few beans and having let the tyres down to 12PSI I was gaining a few feet at a time and the ETC was chattering away very muchly. each time I almost came to a halt I would brake and then select reverse to power back through the ruts (Down hill too) then brake and run up again. Neither once did the brakes not work nor it stall the engine infact it was possible to release the throttle and the engine return to idle without dipping the clutch and the tyres still turning. In the above recovery of the Coffee wagon the drive assist was purely 1st low Idle and the anti stall / Idle jack just let the tyres turn enough to maintain steerage. Any power and the ETC just clicked away futilely. Guaranteed the pedal was firmer after ETC usage but I still could stop and hold the vehicle. Maybe a good few years of commuting in a series IIA with non servo brakes has given me a strong right leg?  |
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15th Dec 2017 7:29pm |
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| zsd-puma Member Since: 09 Aug 2016 Location: Kent Posts: 2720 
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When you have a car that's apparently stuck 'because' the traction control is kicking in, what the ETC is actually doing is stopping you from just spinning the wheels and burying it up to it's axles. Without ETC you'd still be stuck, it's just you'd be able to spin the wheels like crazy and throw mud everywhere. Only in very rare circumstances does the ETC prevent you from getting unstuck.
Another issue with the Discovery you mention is that a Discovery is much more likely to have had heavily road biased tyres on it than a Defender, this could have been your friends problem, rather than the traction control. Wet grass, which is what you find on a typical camp site, is awful stuff for traction. One thing you can do to get traction is put snow chains on, they work in mud as well as snow. |
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15th Dec 2017 11:44pm |
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