Slippy Diff?

[Vidal Baboon]

I decided to see how hard I could launch my Cupra the other day, so turned off the TCS.
In doing so, I was surprised to see two black lines behind me.

So, I was quite puzzled as I did'nt think the Cupra had an LSD.

After reading somthing on here a while ago, I was under the impression that the TCS does not fully disengage anyway regardless of how hard or how many times you push the button

After further reading (read- confusion) how does the TCS work?

By braking the wheel with the least grip- the spinning one? Or, does it just back the power off progressively until the wheel spin is under control?

 

[GainfulShrimp]

I think you're mixing up TCS and ESP. You can turn off ESP (which includes TCS), but it will still intervene to a much lesser extent. I believe turning off ESP would allow a lot of wheelspin but other safety features - e.g. ABS - are always on regardless of the setting.

 

[wayne lcr]

why would you want to do this any way and u carnt turn tcs like gain said you turn the esp so called of but it does not turn it of complete no matter what

 

[KzJF]

How does it 'not turn off completely' ?
I know ABS is impossible to turn off without manually disabling the sensors.
Anything else stays on?

 

[Vidal Baboon]

How does it 'not turn off completely' ?
I know ABS is impossible to turn off without manually disabling the sensors.
Anything else stays on?

I've got no idea- but plenty of systems on other cars will always have nanny there to back you up- I know on the new MX5, you have to hold the button down for about 12 seconds for it to turn completly off.


With regards to the ABS question, where did that come from? Yes the system may use the sensors-
With regards to the new Cupra R & other hot VW's comming through- I thought they were going to be using this type of TCS. Which is, as I understand, not fitted to the Mk2 Cupra?




Before this whole thread goes & turns itself into another internet rumour, I am only going on what I have read on here- briefly (so I may have it wrong) I am after some clarification.

So,

1. Does the MK2 Cupra have an LSD
2. Why did I end up with two black lines following me up the road
3. How does the traction control work (whatever it's called)
4. Why do all threads seem to descend into 'why would you want to do that' type answers?

I thought I logged on to Pistonheads for a moment.

And relax

 

[KzJF]

With regards to the ABS question, where did that come from? Yes the system may use the sensors, but that's not what's I want to know...

I meant to say ABS stays on regardless of what you press.
I wanted to know what else stays on when I turn ESP off.
Sorry for hijacking your thread mate.

 

[Vidal Baboon]

I meant to say ABS stays on regardless of what you press.
I wanted to know what else stays on when I turn ESP off.
Sorry for hijacking your thread mate.

Sorry, not at all- the first paragrah was to hopefully go some way to answer your question.

Just youtube a top gear review on an AMG Mercedes- they all won't let you switch off the TCS unless you use a diagnostic tool or do it through the info centre with some help

 

[n_olympios]

So,

1. Does the MK2 Cupra have an LSD
2. Why did I end up with two black lines following me up the road
3. How does the traction control work (whatever it's called)
4. Why do all threads seem to descend into 'why would you want to do that' type answers?

1. No.
2. Because by pressing the TCS/ESP button, you disengage the traction control system completely and the ESP partially.
3. Wheel spins, engine cuts out to reduce spin (actually it doesn't exactly cut out, it just stops revving until the wheel regains traction).
4. Couldn't answer that.

Just to clarify things for you, the TCS and the ESP are two different things.

TCS does what I mentioned in (3) and can be disengaged completely, which is why you were left with the two black lines.

The ESP uses the brakes when the car loses traction when cornering, for instance if it oversteers or understeers it applies the brake on a specific wheel to stabilise the car. For all cars up to MY09, ESP could be fully disabled. For MY09 on, it can be only partially disabled, which basically means that it lets the car go into weird angles whilst cornering, but if it feels that the angle becomes much bigger then it engages and brings it back to normal.

The facelifted Fr's/Cupras have, in addition to the above, an electronic system called XDS, which simulates an LSD (Limited Slip Differential) when cornering.

Also, in relation to your OP, the existence of an LSD doesn't necessarily mean that there won't be any wheelspin from standing start.

 

[Vidal Baboon]

Thanks for taking the time to reply.

I understand the car car still spin up the front wheels with an LSD- I had a 200bhp series 1 RS Turbo which would have no trouble lighting them up!.

The part that threw me was, why I had 2 black lines following me up the road as opposed to 1- without LSD it'll spin up whichever wheel it's easiest to transmit
Power through- which usually will leave you with 1 line.

 

[n_olympios]

No it won't. In a straight line, the standard differential will still transmit the power equally to both wheels, if there's no massive difference in their traction. For that to happen, one wheel should be on dry tarmac and the other on gravel or snow. In that case, you just wouldn't go anywhere. One wheel would be still and the other getting all the power would just spin on the same spot.

Again, with LSD it'll still spin the wheel that's easier to transmit power through, just not at the same percentage. That's why you usually get torque steer on cars with LSD's (Focus MkI RS was a great example of this).

 

[Vidal Baboon]

No it won't. In a straight line, the standard differential will still transmit the power equally to both wheels, if there's no massive difference in their traction. For that to happen, one wheel should be on dry tarmac and the other on gravel or snow. In that case, you just wouldn't go anywhere. One wheel would be still and the other getting all the power would just spin on the same spot.

Well is'nt that what happens with an open diff?

Again, with LSD it'll still spin the wheel that's easier to transmit power through, just not at the same percentage. That's why you usually get torque steer on cars with LSD's (Focus MkI RS was a great example of this).

I always thought Torque steer was a culmination of many things, not just having a grabby LSD.

In any rate, I assumed the tug on the wheel was from the power being shot across the different driving wheels- i.e. One spins, then the LSD reigns it in, the power transmits to both wheels, the the LSD eases off- the wheel spins up and the cycle repeats.

It's the first time I've seen a car light up both wheels simaltaneously without an LSD or electronic aid- as you said to mimic a mechanical one.

 

[jcp]

In a straight line and on a consistent surface the LSD- if there was one- would have no work to do. An ordinary differential allows the wheel with less grip to spin away power, an LSD prevents one spinning away if it loses traction.
So two black lines are the norm- and jolly good, if tyre chewing, fun. With some lock applied or if one tyre is on a low grip surface one black line would be the outcome.

 

[chrisboyle999]

stick with this until the last few seconds to appreciate why you shouldnt drive with the esp off for any length of time

i was lucky enough to get to have a thrash in a seat uk cupra and believe me the difference in driving with it off as oppose to on is massive.
launching the cupra properly has alot more to do with how you press pedals, not which buttons you press.

 

[n_olympios]

Sure, torque steer comes from various factors, not only LSD. I wrote it the wrong way in my previous post.

I'm probably not the best one to try and explain how mechanical things work (especially when not using my native language), but what you're describing is indeed similar to the TCS function. The LSD doesn't "ease off"; how can it, since it's a total of clogs and axles, uninterruptingly connected to the engine (through the gearbox, of course)?

In a straight line (and with no traction difference), it transmits the power equally to both wheels, 50% of the power to each. When one wheel has less traction than the other, it still spins, just at a smaller rate compared to a "free" differential. That rate depends on how the LSD is built. The main difference is though that the wheel with traction will still get 50% of the total power coming from the engine.

I hope I've got this right and aren't talking nonsense here.