FWD + Under/Oversteer + traction control...
Discussion
I am hoping some of you guys who actually know what they are doing behind the wheel can answer a few queries I have?
My daily driver is a 2.2 Astra and as such has a fair wedge of power and torque to transmit to the road via the front wheels. It has got traction control and ABS which cannot be switched off.
I found on my 'private' skid pan that turning the wheel and giving it a decent bootfull in 2nd gear just results in wheelspin and understeer...this obviously triggered the TC. I found that when the TC kicked in the car would grip and then slip again when the TC switched off...I also noted that if I turned the wheel more to try and keep the car on my original line when the TC made it grip again obviously the car suddenly turned more than I wanted it to...I then noted that if I kept the steering wheel in the same position the car would continue to wash out wide of where I wanted to be until the traction control found a happy balance of pulsing the brakes to pull me back on to my original path.
So in the event of understeer should I try and turn the wheel more or should I just allow the car to run wide and let the TC eventually pull me back on line?
On to the next bit...with low speed skid pan stuff I couldnt induce any oversteer. What will the TC do in the event of oversteer? Does my TC only work when it senses wheelspin and therefore only works on the front wheels?
My daily driver is a 2.2 Astra and as such has a fair wedge of power and torque to transmit to the road via the front wheels. It has got traction control and ABS which cannot be switched off.
I found on my 'private' skid pan that turning the wheel and giving it a decent bootfull in 2nd gear just results in wheelspin and understeer...this obviously triggered the TC. I found that when the TC kicked in the car would grip and then slip again when the TC switched off...I also noted that if I turned the wheel more to try and keep the car on my original line when the TC made it grip again obviously the car suddenly turned more than I wanted it to...I then noted that if I kept the steering wheel in the same position the car would continue to wash out wide of where I wanted to be until the traction control found a happy balance of pulsing the brakes to pull me back on to my original path.
So in the event of understeer should I try and turn the wheel more or should I just allow the car to run wide and let the TC eventually pull me back on line?
On to the next bit...with low speed skid pan stuff I couldnt induce any oversteer. What will the TC do in the event of oversteer? Does my TC only work when it senses wheelspin and therefore only works on the front wheels?
Rather than keeping it floored and letting the TC sort things out, use throttle modulation to keep you pointed in the right direction. If you ease off the throttle a little in the turn, the vehicle weight will shift forward off the rear wheels, allowing the car to rotate. Under most circumstances, you will not see oversteer in a FWD car, but if you aren't careful in your throttle modulation techniques you can induce lift-off oversteer.
Increasing power to the front wheels increases the slip angle at the front and promotes understeer, the tyres don't care whether that came from the TC or your right foot. You can counteract the understeer by applying more steering lock, but generally once you are above a very small amount of slip more slip equals less grip and you are better easing off the power. That will reduce the understeer and of course you will need to remove some of the extra lock you applied.
Don't fall into the trap of thinking that traction control is a skid control system which will help you in every skidding situation - it isn't. The clue is in the name, traction control, i.e. a system which assists the driven wheels of a car maintain their grip on the road when accelerating.
If you accelerate too harshly and the driven wheels of your Astra start to spin, the traction control will interject by cutting the throttle until the wheels start to regain grip with the road surface. Your correct response to this should be to ease back on the accelerator, otherwise, as soon as the system recognises that the wheels are gripping again, it'll hand control of the throttle back to you, and if you've kept your right foot planted, the wheels will start spinning again, and you're back to square 1.
Your aim should be to keep as much control over the car as you can without the TC cutting in, but if it does cut in, you should respond to that fact, rather than just keeping your foot down and letting the system sort things out for you. adding more steering lock whilst the car is understeering will just add to your problems, because when the grip situation has been sorted out, the wheels will go in the direction they're pointing, which can sometimes be nowhere near where you were intending. Don't apply too much extra lock, but try to bring the car back under control by throttling back.
Traction control can't do much about understeer caused by excessive speed in a corner, as this isn't generally associated with wheelspin. For an in-depth look at how to control understeer under those circumstances, read my post here...
www.pistonheads.com/gassing/topic.asp?t=368019&f=154&h=0
TC won't do anything to help you if you end up oversteering your Astra either. Oversteer is caused by a lack of grip to the back wheels, and your driven wheels are at the front, so it won't help you out. See the above post for information on catching oversteer.
I think you may have confused simple traction control with one of the more complicated modern systems such as ESP or DSC which monitor lots of different factors about the car and have various options to help you control a skid.
If you accelerate too harshly and the driven wheels of your Astra start to spin, the traction control will interject by cutting the throttle until the wheels start to regain grip with the road surface. Your correct response to this should be to ease back on the accelerator, otherwise, as soon as the system recognises that the wheels are gripping again, it'll hand control of the throttle back to you, and if you've kept your right foot planted, the wheels will start spinning again, and you're back to square 1.
Your aim should be to keep as much control over the car as you can without the TC cutting in, but if it does cut in, you should respond to that fact, rather than just keeping your foot down and letting the system sort things out for you. adding more steering lock whilst the car is understeering will just add to your problems, because when the grip situation has been sorted out, the wheels will go in the direction they're pointing, which can sometimes be nowhere near where you were intending. Don't apply too much extra lock, but try to bring the car back under control by throttling back.
Traction control can't do much about understeer caused by excessive speed in a corner, as this isn't generally associated with wheelspin. For an in-depth look at how to control understeer under those circumstances, read my post here...
www.pistonheads.com/gassing/topic.asp?t=368019&f=154&h=0
TC won't do anything to help you if you end up oversteering your Astra either. Oversteer is caused by a lack of grip to the back wheels, and your driven wheels are at the front, so it won't help you out. See the above post for information on catching oversteer.
I think you may have confused simple traction control with one of the more complicated modern systems such as ESP or DSC which monitor lots of different factors about the car and have various options to help you control a skid.
For what it's worth I totally agree with R_U...
Your car doesn't have a limited slip differential, so with a lot of torque on tap you will tend to smoke the inside front on a turn. Keeping your foot planted and relying on TCS will result in fun and games on a skid pan, but the results in my experience are too erratic to rely on in a real life situation... you won't be able to maintain a smooth line with TCS jumping in and out.
As R_U says, TCS is only there to stop the wheel spinning under over-power - usually in 1st and 2nd - so if you feel the system operating on a corner, then ease off (just enough to regain proper grip) to maintain greater control over the balance of the car... Obviously if you're just trying to get away in the wet in a straight line then keep it planted - that's likely the situation where TCS will/should deliver the best results.
Personaly I hate these kinds of systems, which is why I go for 4wd. Mind you I'm a Luddite... It took me a few years to submit to buying a car with ABS!
Your car doesn't have a limited slip differential, so with a lot of torque on tap you will tend to smoke the inside front on a turn. Keeping your foot planted and relying on TCS will result in fun and games on a skid pan, but the results in my experience are too erratic to rely on in a real life situation... you won't be able to maintain a smooth line with TCS jumping in and out.
As R_U says, TCS is only there to stop the wheel spinning under over-power - usually in 1st and 2nd - so if you feel the system operating on a corner, then ease off (just enough to regain proper grip) to maintain greater control over the balance of the car... Obviously if you're just trying to get away in the wet in a straight line then keep it planted - that's likely the situation where TCS will/should deliver the best results.
Personaly I hate these kinds of systems, which is why I go for 4wd. Mind you I'm a Luddite... It took me a few years to submit to buying a car with ABS!
Edited by scoobmeister on Monday 19th March 23:23
Thanks a heap for all the advice guys!! This is the sort of stuff that seperates someone that doesnt have a clue like me from the pro's! I am trying to improve that but I cant find a good advanced drivers course to do here in oz..
I think I will go and book me a trackday with an instructor alongside to try and understand the car a bit more...
I think I will go and book me a trackday with an instructor alongside to try and understand the car a bit more...
scoobmeister said:
For what it's worth I totally agree with R_U...
Your car doesn't have a limited slip differential, so with a lot of torque on tap you will tend to smoke the inside front on a turn. Keeping your foot planted and relying on TCS will result in fun and games on a skid pan, but the results in my experience are too erratic to rely on in a real life situation... you won't be able to maintain a smooth line with TCS jumping in and out.
As R_U says, TCS is only there to stop the wheel spinning under over-power - usually in 1st and 2nd - so if you feel the system operating on a corner, then ease off (just enough to regain proper grip) to maintain greater control over the balance of the car... Obviously if you're just trying to get away in the wet in a straight line then keep it planted - that's likely the situation where TCS will/should deliver the best results.
Personaly I hate these kinds of systems, which is why I go for 4wd. Mind you I'm a Luddite... It took me a few years to submit to buying a car with ABS!
Your car doesn't have a limited slip differential, so with a lot of torque on tap you will tend to smoke the inside front on a turn. Keeping your foot planted and relying on TCS will result in fun and games on a skid pan, but the results in my experience are too erratic to rely on in a real life situation... you won't be able to maintain a smooth line with TCS jumping in and out.
As R_U says, TCS is only there to stop the wheel spinning under over-power - usually in 1st and 2nd - so if you feel the system operating on a corner, then ease off (just enough to regain proper grip) to maintain greater control over the balance of the car... Obviously if you're just trying to get away in the wet in a straight line then keep it planted - that's likely the situation where TCS will/should deliver the best results.
Personaly I hate these kinds of systems, which is why I go for 4wd. Mind you I'm a Luddite... It took me a few years to submit to buying a car with ABS!
Edited by scoobmeister on Monday 19th March 23:23
Agree. Im a luddite too. I even make a point of having my scoobs without ABS. But i do drive in the snow a fair bit I suppose. Prefer to have good brakes and know at what point they are about to lock.
Edited because the ludite couldnt operate his computer properly!
Edited by Scoobman on Tuesday 20th March 18:59
R U has it right.
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability you'll recognise the start of loss-of-traction as it occurs and modulate the throttle accordingly - all TC does IMHO is encourage the feckless and clueless to keep the throttle nailed more of the time 'and let the electronics sort it out' (My brother sadly being one of them...but he won't be told!).
ABS has value, in that it (well, a good system anyway) shortens braking distances for all bar the best drivers. ESP-type programmes I can see have a place in powerful cars. But for the masses?!? Not IMHO.
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability you'll recognise the start of loss-of-traction as it occurs and modulate the throttle accordingly - all TC does IMHO is encourage the feckless and clueless to keep the throttle nailed more of the time 'and let the electronics sort it out' (My brother sadly being one of them...but he won't be told!).
ABS has value, in that it (well, a good system anyway) shortens braking distances for all bar the best drivers. ESP-type programmes I can see have a place in powerful cars. But for the masses?!? Not IMHO.
havoc said:
ESP-type programmes I can see have a place in powerful cars. But for the masses?!? Not IMHO.
I completely disagree. Stability programmes help enormously with the control of a car in emergency situations, making it more likely that the car will go where the driver wants it to and not into an obstacle or off the road. An example of a situation where ESP might help would be a swerve to avoid a large animal which entered the road unexpectedly. The ESP can achieve greater car control than the most skilled driver, by applying braking to the four wheels individually. This is just as applicable in low powered vehicles as in high powered vehicles, and though less skilled drivers may need the help of ESP more, highly skilled drivers can benefit also.
I believe that there has been research to show dramatic reductions in single vehicle accidents by cars with stability control, although I cannot point you to it. Now that ABS is required in all new cars, I don't suppose it will be long before stability control is also mandatory. Bring on ESP for the masses, say I.
Since this is the Advanced Driving Forum, I had better not forget to mention that the Advanced Driver should avoid getting into any situation from which he needs a stability programme to extricate him!
By the way, on the question of terminology RU Local highlights the difference between traction control and stability programmes. I agree that there is confusion: the term 'traction control' is sometimes used generically to cover a wide range of systems including stability programmes. It would help avoid confusion if the manufacturers would agree on standard terminology and stop trying to pretend that their offering is something different from everyone else's, when ESP, DSC, DSTC, ASC, PSM and no doubt many other systems all do the same thing.
Do try to work out what your own car is fitted with and consider the implications.
havoc said:
R U has it right.
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability…
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability…
Nail hit squarely on the head there. Unfortunately, there are too many drivers out there who possess a very low level of driving ability for whom traction control is a benefit. I personally don’t like the system in FWD cars, and I generally turn it off as I find it’s responses too binary and lacking any subtlety. I much prefer to retain full control of the throttle myself, but I’ve had the benefit of some extensive training and experience, which the majority of drivers haven’t had. I’m selfish in that I’d prefer to know everybody else has the system, as I don’t rust them, but I’d rather not have it myself.
havoc said:
ABS has value, in that it (well, a good system anyway) shortens braking distances for all bar the best drivers. ESP-type programmes I can see have a place in powerful cars. But for the masses?!? Not IMHO.
I’m afraid you’ve fallen into the trap that most people fall into with that statement. It’s a very common misconception, and one which the manufacturers, in my opinion, don’t do enough to rectify. Green V8S has the right idea…
GreenV8S said:
Very good ABS systems may indeed shorten the braking distance, but I think the main reason that they're used is to retain steering control under emergency braking.
I haven’t found a car yet in which, under ideal braking conditions, I can’t beat the stopping distances with the ABS fuse removed. ABS does not make your car stop in a shorter distance – it [I]can’t, [/I]because it’s modus operandi is to quickly release the brakes and reapply them many times a second. If a driver is capable of holding a car just at the point before lock-up, then they’ll stop in a shorter distance than if the ABS has activated.
What ABS does do, however, as GV8S put so succinctly, is allow the driver to brake with maximum efficiency, whilst still allowing them to steer. Again, this is a safety system designed with a drivers basic reaction in mind – most average drivers will stamp on the brakes in an emergency, and without ABS, this will mean that they’ll slide straight on, irrespective of their steering input. ABS effectively applies cadence braking at a much faster rate than anyone can do with his or her right foot.
Again, my personal preference would be not to have ABS myself, but for everyone else to have it. However, my own car has it fitted and it’s not switchable, so I leave it on.
Oops! 
Very good point Peter and Reg re: ABS.
That said, I've found the Honda system to be very good, while the system on my Focus (and on the Transit...guessing the same thing) to be diabolical, virtually removing all braking effort by being too intrusive... over Xmas I actually had to cadence-brake to stop the ABS from stopping the car stopping!!!
Mark - possibly. But for my mind if you have that you've got to have TC as well, and then you've got a throttle potentiometer not a throttle cable, and I can't STAND non-switchable TC, nor the lag you get with a throttle potentiometer (If I wanted lag I'd drive a turbo'd car, not a n/a one!!!). And yes, my next car is likely to be older than the current two as even Honda have gone down the potentiometer route...
Very good point Peter and Reg re: ABS. That said, I've found the Honda system to be very good, while the system on my Focus (and on the Transit...guessing the same thing) to be diabolical, virtually removing all braking effort by being too intrusive... over Xmas I actually had to cadence-brake to stop the ABS from stopping the car stopping!!!
Mark - possibly. But for my mind if you have that you've got to have TC as well, and then you've got a throttle potentiometer not a throttle cable, and I can't STAND non-switchable TC, nor the lag you get with a throttle potentiometer (If I wanted lag I'd drive a turbo'd car, not a n/a one!!!). And yes, my next car is likely to be older than the current two as even Honda have gone down the potentiometer route...
R_U_LOCAL said:
I haven’t found a car yet in which, under ideal braking conditions, I can’t beat the stopping distances with the ABS fuse removed. ABS does not make your car stop in a shorter distance – it [I]can’t, [/I]because it’s modus operandi is to quickly release the brakes and reapply them many times a second. If a driver is capable of holding a car just at the point before lock-up, then they’ll stop in a shorter distance than if the ABS has activated.
That must be part of it, but that's something that technological improvements will gradually overcome i.e. the ability to maintain the desired slip percentage accurately. Where the human driver has a real advantage is the slip percentage that the ABS tries to achieve. To provide lateral grip under slippery conditions it has to maintain a very low slip percentage, well below the level for optimal straight line braking in very grippy conditions. Unless/until you have an ABS system which can dynamically work out the optimum slip percentage under varying road/tyre conditions and optimise the trade-off between lateral and longitudinal grip depending what the driver is trying to do, the advanced human driver has an advantage. Meanwhile the ABS system has the advantage of far quicker reactions than any human and the ability to fiddle brake.
havoc said:
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability you'll recognise the start of loss-of-traction as it occurs and modulate the throttle accordingly - all TC does IMHO is encourage the feckless and clueless to keep the throttle nailed more of the time 'and let the electronics sort it out' (My brother sadly being one of them...but he won't be told!).
Problem is TCS is often not smooth, which unsettles the car more than a smooth increase and decrease in slip ratio as you lift the throttle yourself.
Even a fwd with runaway wheelspin is pretty benign, it's the rapid change of state of front grip that is the issue!
Dave
Mr Whippy said:
havoc said:
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability you'll recognise the start of loss-of-traction as it occurs and modulate the throttle accordingly - all TC does IMHO is encourage the feckless and clueless to keep the throttle nailed more of the time 'and let the electronics sort it out' (My brother sadly being one of them...but he won't be told!).
Problem is TCS is often not smooth, which unsettles the car more than a smooth increase and decrease in slip ratio as you lift the throttle yourself.
Even a fwd with runaway wheelspin is pretty benign, it's the rapid change of state of front grip that is the issue!
Dave
....especially if you have a good deal of steering lock on at the time and you don't actually want to make a sharp turn! This is not entirely a joke. I've found it can be a problem in winter conditions.
BTW, Dave - many thanks for your message. I'm glad you're in agreement about a tootle out. All we need now is co-operation from Mr Local.
Reg - I tried to send a PM to you and it didn't seem to get through, but I'm always happy to receive them if you're minded to communicate.
Best wishes all,
Dave.
TripleS said:
....especially if you have a good deal of steering lock on at the time and you don't actually want to make a sharp turn! This is not entirely a joke. I've found it can be a problem in winter conditions.
Indeed, when playing a bit (naughty me) exiting roundabouts I've often pushed the fronts to spin a little in greasy conditions, and the best option is to take a bit of lock off (key) with a mild lift of throttle.
Anything more than 50% throttle off with significant lock = quick front weight transfer, more front lateral grip and a sudden bout of yaw moment
Dave
Edited by Mr Whippy on Thursday 22 March 15:46
TripleS said:
Reg - I tried to send a PM to you and it didn't seem to get through, but I'm always happy to receive them if you're minded to communicate.
Best wishes all,
Dave.
Best wishes all,
Dave.
My apologies - I don't check my emails as often as I should. I have recieved your PM, and I've sent you a reply.
R_U_LOCAL said:
TripleS said:
Reg - I tried to send a PM to you and it didn't seem to get through, but I'm always happy to receive them if you're minded to communicate.
Best wishes all,
Dave.
Best wishes all,
Dave.
My apologies - I don't check my emails as often as I should. I have recieved your PM, and I've sent you a reply.
Yes I have it thank you Reg. I was just afraid that you were not accepting messages via PH.
I look forward to sorting something out with you.
Best wishes all,
Dave.
Mr Whippy said:
havoc said:
Personally I can't see ANY need for TC in a fwd car...if you've any driving ability you'll recognise the start of loss-of-traction as it occurs and modulate the throttle accordingly - all TC does IMHO is encourage the feckless and clueless to keep the throttle nailed more of the time 'and let the electronics sort it out' (My brother sadly being one of them...but he won't be told!).
Problem is TCS is often not smooth, which unsettles the car more than a smooth increase and decrease in slip ratio as you lift the throttle yourself.
Even a fwd with runaway wheelspin is pretty benign, it's the rapid change of state of front grip that is the issue!
Dave
I found that if I let the TC try and fix the problem the car started a weird bobbing motion...grip, slip, grip , slip but then eventually it would control the throttle to the point of the car going all of 0.00004KMH..
Controlling the throttle myself is the preffered option
. I would like to get on a proper skid pan or trackday though to see what happens at higher speeds with the weight shift..Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff