 | Home > Puma (Tdci) > ABS/ Traction Control - was it standard on the Puma 2.4? |
 
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
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The problem with ABS on a failed hill climb is not the ABS but the traction control.
When that's been working hard but still hasn't got you to the top of the hill it can effectively lock the brake pedal out and give you no braking. Most techniques for regaining control on a hill require the use of the brakes to stop the vehicle before putting it in to reverse so not being able to use them is an issue. Going back to whether traction control is needed or not... I don't have it. I've driven over stuff I couldn't walk up or down and haven't had issues *yet*. That said, there are some scenarios where it will help and the fancy TC on a Disco 4 is incredibly impressive when you see it in action. I've been driving some tracks that someone else has been driving a Jeep Renegade Trailhawk on - that is extremely reliant on the TC. Even in full 4WD, the Jeep needed the traction control to keep control where I didn't. Equally I've seen a TC equipped Land Cruiser just slide off the edge of a track and down a hill and it wasn't until his centre diff lock was engaged that he went where he wanted to. I'd say technique, tyres and tire pressures were more important in a Defender, and you can always fit lockers or ATB diffs if you're struggling off road. |
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13th May 2016 6:21pm |
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| TfredJ Member Since: 19 Jul 2016 Location: Napier Posts: 3  
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I am just thinking of upgrading my old Stage-One V8 tipper for a newish Puma tipper, it is mainly for use on my rural property and I have some steep grass paddocks, having driven a friends Disco4 on the steep sections his traction control helped him go places that my old Stage-One would not go when it lost a single wheel traction on the wet grass and even though the centre diff lock helps it could not follow the Disco, my friend was driving my old girl and he has way more off road driving experience than me so I have to assume that TC can out perform a good driver on steep slippery grass slopes and that is what I need to do.
Going back to the original thread question, is there an easy way to identify if TC id fitted, is there a TC OFF SWITCH like you get in rad cars? |
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19th Jul 2016 10:51pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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if you otherwise like your current Land Rover, the other option would be to fit ATB or locking diffs to it.
The Puma does bring various advantages but you don't have to change to a Puma to get more traction. |
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20th Jul 2016 11:25am |
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| Riccarton Member Since: 10 Aug 2015 Location: Gods' Own Country Posts: 280  
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Once you're confident with left foot braking you don't necessarily need abs to induce traction control
Apply enough braking force to equal out the torque the gripping wheels can stand and hey-presto - TC on a non TC vehicle. |
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20th Jul 2016 9:17pm |
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| agentmulder Member Since: 16 Apr 2016 Location: Outer Space Posts: 1324 
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I really want learn this technique
Opportunity hasn't cropped up yet though, no matter how hard I try  Solved the bowel problem, working on the consonants... |
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20th Jul 2016 10:05pm |
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| TfredJ Member Since: 19 Jul 2016 Location: Napier Posts: 3
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The main reason for looking at a newish Puma is I would like the extra wheelbase, currently the V8 is a 109 and it gets very light on the front end when loaded due to the large rear overhang, the 130 would be much better balanced when loaded as the rear wheel will be about 2/3 away along the deck whereas currently the rear wheels are forward of the centre of the deck. On a plus point when loaded it makes up for no power steering  As the 130 Cab landy's are seldom available here in NZ I will have to import from UK, then I am up against the emission regs so it would have to be a Puma to meet the specs. What I would really like is a 101 Forward Control, wheel at each corner no overhang! but getting difficult to find a good one now. |
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20th Jul 2016 10:38pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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I don't get how this works. If you've got a system where by the diff can send more torque to one wheel than the other then I can see it makes sense, but with a standard open diff it can't. If you've got a system where the brakes can provide different amounts of braking left and right then that would work, but standard brakes are the same all round aren't they? So if you're applying a certain amount of braking force to both rear wheels and enough torque from the engine to overcome it, won't you just be back to square one with any extra just going to the wheel with no traction? |
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21st Jul 2016 10:16am |
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| Riccarton Member Since: 10 Aug 2015 Location: Gods' Own Country Posts: 280
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Believe me - it works - and it's not exactly a secret!!
Make sure you've got the centre diff' locked first
The best way to think about it is this (just using round figures - not calculated): Assume your ascent requires 50Nm of torque to climb delivered equally across all wheels. Once one of those wheels loses traction then that torque figure will fall off a cliff and you'll come to a standstill with one (or two - if diff' lock is engaged) wheels spinning. Now, if you apply the brake to generate a pre-torque load of 50Nm then regardless of traction for each wheel you've already applied the max load each wheel will need to transmit. Therefore even if one (or two) wheels have zero traction they still have the same torque pre-load on them - so why should they spin? In reality it seldom occurs so perfectly and usually just ends up as a brief stab and hold of the brake to maintain momentum. If you want to test the theory go and cross-axle your car so it's stuck - even in diff-lock - then with the wheels being driven apply left-foot braking. Hey presto - you'll move forwards!! I hope I've explained that ok |
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21st Jul 2016 10:45am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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I'm still not convinced by that I'm afraid. I'm not saying it doesn't work, I'm just struggling to understand how it works.
Say you need 50Nm per wheel (200Nm total), and there is plenty of traction for two wheels but the other two can only get enough traction to create 20Nm reaction torque - so those wheels spin. The differentials front and back are sharing out the torque even left and right, so the left side gets 20Nm and spins, the right side gets 20Nm and stays still. What you need is to be able to put more torque to the right side, so that the left axle has 20Nm through it and the right has 80, that then adds up to create the 200 needed over all to move the vehicle. That's possible with a limited slip, ATB or locking differential in some form. Now, say we apply the brakes to all four wheels. They apply a force to the disk that translates to 30Nm at the axle. Now to spin the wheel on the left we need 20Nm from the surface, plus 30Nm from the brake. So a maximum of 50Nm down the left shaft. The open diff then sends the same 50Nm down the right shaft which overcomes the 30Nm braking torque and leaves 20Nm available to drive, so we're in the same scenario as before. Now in addition to that not working, static friction tends to have a greater hold than dynamic - imagine a box on a slope that's stopped, but if you poke it then it moves and doesn't stop. So by that logic the brake will actually apply more force to the stationary wheel and less to the spinning one. I'm obviously missing something but could someone more intelligent than me point out what it is please? Back on topic... ABS and TC on 130s was a pretty rare option I thought, I'm pretty sure it wasn't even an option until fairly late on. It's more unusual to have it on a 130 than on a 110. |
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21st Jul 2016 11:56am |
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| Naks Member Since: 27 Jan 2009 Location: Stellenbosch, ZA Posts: 2634  
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indeed, I used this technique in my previous 110 Td5 when it got cross-axled. Just a very gentle application of the brakes until the wheels that are spinning start slowing down, then you're moving again. As a matter of interest, you can also use this technique on modern LRs: I did just that when I drove the Evoque at the LR Experience track to make up for the lack of suspension travel. -- 2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear 2015 Range Rover Sport V8 Supercharged 
Defender Puma Workshop Manual: https://bit.ly/2zZ1en9 Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ |
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21st Jul 2016 1:16pm |
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| Jukathy Member Since: 25 Jan 2015 Location: Berlin Posts: 170 
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Yeah. Wheels without grip are slowed down and cannot spin. Anybody else wondering why brake pads wear out too early? |
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21st Jul 2016 1:25pm |
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| Devon-Rover Member Since: 22 Jan 2015 Location: South Devon Posts: 913 
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Quoted from myself in the fender at Glastonbury post.
"When you are stuck or say crossaxled (Simply two opposing wheels spinning) then that is when a bit of left foot braking works. The axle differential is a fickle device and will transmit the vehicles power (Turning motion) to the path of least resistance. So left foot braking comes into play. (Why left? Well you are holding a steady throttle with the right) So to put it simply you have a axle and one wheel is spinning all the power is going to the path of least traction. You apply a gentle left foot brake. *When the brakes are applied they will act on each disc with a similar force This acts upon the spinning wheel and starts to slow it down, now your still applying power with the throttle so this has to go somewhere and what happens is when you have applied enough brake the resistance will be balanced and power then will be split by the differential equally. What happens is that by forcing this equal power split (You are now asking the engine to drive 4 equally braked wheels so equal resistance, Not two low traction and two high traction tyres) With this balance of power through the differentials you also get all four wheels moving. It is with this then you can drive out of the crossaxle of at least split the power better for low traction surfaces. I will add that if you left foot brake do it gently and practice at a play day or somewhere you are allowed to practice offroad driving. What you are doing is simply adding a very high load to the entire drive train and it won't thankyou for it when these loads get too high. It takes a bit of finesse to get the right amount of braking to balance things and enough power not to stall the vehicle. ETC is the same theory just that it is smart enough not to apply to the non spinning wheel (the one with more traction)" It does work but it isn't as effective as ETC but better than nothing |
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21st Jul 2016 1:57pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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OK, so you're saying that by using the brakes the open diff sends equal amounts of torque either direction. No question there, that's what an open diff does. But in this scenario, that's not what we need, we need more torque on one side than the other. Don't we?
I can see that if you're on the brakes and therefore slowing the spinning wheel then quickly come off them, the spinning wheel will want to accelerate, accelerating requires some force that's not required to accelerate the other side so some torque transfer will happen, but only in the split second over which the free wheel is getting up to speed. In all other scenarios you're increasing the torque required to spin the free wheel from the amount of traction the surface provides to the traction plus the dynamic friction of the brakes. Meanwhile the wheel on the side with traction either gets the same amount of torque as the low traction surface provides or in the second scenario it's the low traction surface, plus the dynamic braking force on the opposing side, minus the static braking force (which is higher than the dynamic friction). Everything I think I know about mechanics tells me that applying the brakes evenly makes the problem worse. I realise I'm being that really irritating person that just doesn't get it, but I just don't get it  |
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21st Jul 2016 3:08pm |
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| Riccarton Member Since: 10 Aug 2015 Location: Gods' Own Country Posts: 280
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I think it wise to avoid hard facts - yes the wheel without traction will continue to "spin" so it isn't a transfer of torque. More of an evening out.
Looking at a box sliding down a slope - yes, a stationary object requires more force to overcome the static effect but - - just because a box starts to slide doesn't mean it will acccelerate constantly. Something moving faster generates more friction than something moving slower. I think it'd be wise to go and try the cross-axle example then not worry about the science - just accept it |
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21st Jul 2016 4:15pm |
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