Voices

The case for leaving electronic stability control on for racetracks…

Electronic stability control is a lifesaver on a passenger car, but do we need to leave it on when driving on racetracks?

PUBLIC ROADS are bitumen, just like racetracks, but that’s about where the similarity ends. A racetrack is built for high speed safety with runoffs and barriers, traffic only flows in one direction, everyone there has accepted some level of risk inherent in the activity, cars are scrutineered for safety every time they are allowed on, medics are waiting in their ambulance, there’s no junctions (pits don’t count) and it’s generally an area for you to explore the limits of your car.

So while leaving electronic stability control (ESC) on for public roads is the only sensible, responsible choice, the argument for racetracks is less clear cut that it would appear. The default reaction would be to switch everything off, and I have a lot of sympathy with that view. After all, the attraction for driving fast for most people is the satisfaction of achieving a high-quality lap (not the same as a fast lap) and if the computers are doing part of the job, then that satisfaction is diminished.

But on the other hand, there’s money and safety. Let’s look at reasons to leave those electronics on.

Few people at entry level motorsports have the means to not worry about writing a car off at an event – for many of us, our track car is our daily driver. Then there’s the safety of the driver to consider. Despite all that safety gear, racetrack accidents run a very real risk of injury and even if you can afford to buy another car every week, some injuries can’t be fixed with money. And then there’s the safety of others to consider – it’s a bit unsociable to smash into someone else’s car. Finally, if you crash, your day is over and even the richest people can’t buy more time in the day.

So the logical, sensible decision would be to reduce the risk of a crash which means leaving ESC turned on. In fact, the logical, sensible decision would be to not even bother attend a trackday, so we can’t overplay the sensible side of things. Clearly, there’s a balance to be found, but no real discussion can be hand unless everyone truly understands what are commonly referred to as “the electronics” or “traction control” really is and how it works, and it’s worth digging into this a bit further if you’re an enthusiast driver.

Whenever a car corners it will slide, ever so slightly, even your grandpa in his Camry. This means the tyre is pointing in one direction, and the car is traveling in another. The technical term for this is ‘slip’, and for maximum speed there is an optimum amount of slip for any given car on any given surface. Briefly, the higher speed the corner and the greater the grip the less the slip, which is why F1 cars barely slip at all, whereas rally cars slip a great deal and the quickest way around a motorkhana is to use the parkbrake. If you go beyond the optimum slip angle it is spectacular but slow. That’s slip, now for more familiar terms. You probably know what understeer and oversteer is; understeer is when the car runs wide and you feel like winding on more steering lock to make the corner, and oversteer is when the back steps out and the car over-rotates, requiring opposite lock to correct.

ESC on a roadcar is tuned to detect and correct understeer and oversteer even before the driver notices it. It does this by braking individual wheels, and where necessary, using a seperate but related programme called engine traction control to reduce the power. It may also use a third programme called brake traction control to brake a single drive wheel that is spinning. That’s just three, distinct but related programmes so lumping them all under the banner of “traction control” is right only at the highest level, and enthusiast drivers really need to understand the nuances if they’re to get the best from their vehicles. Every manufacturer has a different name for the same thing, and there’s several more related programmes all helping keep the car rubber-side down. Roadcar ESC does not allow a car to approach its optimum slip angles in most situations, so the car cannot achieve its best laptime with ESC enabled….but it doesn’t necessarily follow that ESC is the limiting factor because unless you’re very, very good – better that you think you are, in most cases – the actual barrier to quicker times is the driver. I’ll say that again – in most cases the barrier to quicker laptimes is the driver not ESC. Even if you switch ESC off and go faster, that may not be any quicker than a skilled driver with ESC on.

Now that’s plain old ESC on a plain old roadcar. Sportscars worthy of the name have the same ESC design but a different calibration. They generally have three or more options; all on, sport mode, all off. Roadcars usually have just all on and off, and generally off isn’t entirely off, just de-sensistised. The sportscar all-on mode differs from a roadcar all-on mode as it typically allows a bit more slip, and the sport mode even more slip again, to the point where any more would be counter-productive on a racetrack. Only then does ESC intervene. The all-off mode is exactly that, all ESC off although ABS and perhaps brake traction control (explanation here) is usually left enabled.

Here’s the Lexus RC F‘s four driving modes as an example:

Sometimes these modes also affect other things such as gearshift points and throttle maps, and but on the better set up cars each is indvidually adjustable.

So the main reason people want to switch ESC off – because it “slows them down” – is a fallacy. If you have your ESC set to sport mode in a reasonably modern sportscar, which is most cars from 2012 onwards, then the limiting factor is probably you, not the car. If ESC activates you can and should think of it as a little driving coach, telling you that you could have been smoother. For example, did you accelerate without unwinding steering lock? Did you have a second bite at that corner because you weren’t looking far enough ahead? Was your foot just a little too harsh on the throttle? With time, you know that such less-than-perfect driving inputs will pre-empt an ESC intervention, much like when you were little and back-chatted your parents – you knew retribution was going to come your way.

Here’s another little ESC tip. The ESC computers don’t just look for the slip angle, they look at how fast you’re likely to exceed the slip angle. In other words, approach the limit smoothly and gently and ESC stays quiet, just like creeping up on a sleeping dog. But if you go screaming up to the limit, ESC cuts in well beforehand…just like scaring a sleeping dog away if you come at it yelling. It is possible to have your boring old roadcar squealing all four tyres and not have ESC kick in, let alone a sportscar. You just need to be creamy-smooth, and correctly creamy-smooth.

For example, ESC looks at what you’re doing with the controls, primarily the steering wheel. It assumes that the steering wheel is pointed where the driver wants to go, so if you’re understeering while accelerating it’ll decide your desired arc is, and will exceed the grip limits so it will reduce throttle and brake the inside wheels a touch as you’ve already exceeded the optimum slip limit, and show every sign of just going further beyond.

A bad driver will interpret this as interference, and in a way it is. But if ESC didn’t interfere, you’d understeer pointlessly and massively, and anyway driving with the throttle hard down while the front wheels are scrubbing is a good way to lose time, ESC or not. If on the other hand you are unwinding steering lock while accelerating then the ESC computers don’t worry as they know as the steering is being straightened there will be less demand for lateral grip from the front tyres. It is even possible to ever so slightly drift the back end on throttle with some cars in some sport modes, just enough to help get the car rotated out of slow corners. But you need to be sooooo smooth, and how’s that a bad thing?

The best sportscar ESC also gives you a chance to correct. Let’s say the back end is a little loose into a fast corner – lift off oversteer – and it starts to, ever so slightly, break loose. If you’re quick, early and smooth ESC will let you do the correction, a bit like when you were being taught to walk and your parents would let you nearly fall over, but not quite. If on the other hand you’re slow or harsh to correct, then ESC will do the job for you.

So we seem to have arrived at an answer. A modern sportscars with a sports ESC mode is going to let you have a whole lot of fun, not slow you down, and provide a potentially life-saving safety aid, and we did some testing with old and new Toyota 86s which proved the point. In about 99% of cases when someone thinks they’re “being slowed by the electronics” it’s normally their technique at fault. Even if you are an ace driver, how will you go when you hit an oil patch, or blow a tyre out, or someone spins in front of you? That’s where you’ll be happy you had ESC watching your back. There’s a reason that F1 banned electronics many years ago, and that was because even the best drivers in the world could turn faster laptimes with a computer helping them out.

And yet. Some ESC systems are so good, and so unobtrusive they may actually be dangerous. If you drive with them always on, then you may not know that electronics are saving you lap after lap. You become convinced of your own skill, and all is well until one day you drive a car without ESC, or switch it off. And then you find that your understeer is not curbed, your oversteer is not corrected. That could be painful.

So I think the solution is to leave ESC on but have it audibly cut in, so the driver knows it’s activated, but not to feel it. Porsche and Audi seem to disagree, as their calibrations are so sensitive you really can’t feel them at all. Toyota have in the latest MY17 86 got it right – you know when ESC has activated, but it doesn’t slow you down, and unlike some others, it acts only as a safety net not as a driver aid. And I think that’s the way of the future for the best mix of safety and challenge.

Further reading

Robert Pepper

Robert Pepper

Robert Pepper is the editor of PM4x4, an offroad driver trainer and photographer interested in anything with wings, sails or wheels. He is the author of four books on offroading, and owns a modified Ford Ranger PX which he uses for offroad touring. His other car is a Toyota 86 which exists purely to drive in circles on racetracks. Visit his website: www.l2sfbc.com