What is Racelogic's traction control?

Traction control is simply a control system that stops the car wheels from slipping when too much power is put through them and thus cause the car to become unstable in terms of its behavior on the road. Slipping wheels can be caused by a variety of reasons: too much power causing the rear wheels to break traction and start to slipping, changes in the grip offered by the road and changes in the tyre contact patch caused by cornering, braking, accelerating or all three. While these problems are applicable to every car, TVRs have an extremely high power to weight ratio and therefore the opportunity to experience wheel slip is greatly increased, compared with most other cars. It should be remembered that it is not the car that induces wheel spin or tail slides, but in fact the driver failing to compensate for changing conditions or simply not having the appropriate level of skill to drive the car within a safe envelope. As a result, it is often the driver who is the weak link in the car and not the other way around. If you have ever had a good racing driver take your own car round a track, it can seem that the car has gained better brakes, handling and more power. The car hasn’t changed but the “nut” behind the wheel has. In reality, the driver is just making more of the car’s potential.

So it is a good thing to avoid wheel spin? Well... yes and no. The problem is that wheel slip is not all bad and the maximum coefficient of friction occurs when the tyre starts to just starts to slip. This occurs with a slip factor of about 10% in the dry and about 5% in the wet. The difficulty is that this is a very fine line. If too much wheel spin occurs the levels of grip that are offered are dramatically reduced and the car will either stay, still spinning its wheels, or more usually, start a tail slide which if not corrected will cause the car to start spinning and skid. Too little or no wheel spin may be cautious but is not exploiting all the level of grip that is available.

To drive the car quickly requires treading this fine line. This means that the driver has to be able to detect when too much slip is happening and then reduce the power to correct it. The question is recognising the onset and working out how much correction to apply. Very often the difference between fast and slower drivers is the level of experience in judging where the safe envelope exists. Get it wrong and the slippage can become a full blown tail slide.

The need for a faster response is another problem. The human nervous system can take several tenths of a second to detect a change in the car's motion and apply some form of correction. In practice this means that most drivers drive within a lower envelope so that there is a greater level of safety. For experienced rally drivers, the margin is small and they can typically achieve 90% of the maximum traction. They usually have very fast reactions. Less experienced drivers will achieve between 60-70% of the maximum traction.

The real issue for drivers is that the envelope will also change depending on road conditions and even other factors such as temperature, tyre tread depth and so on. The other difficulty faced by TVR drivers is that the levels of grip and performance offered by these cars is so high that when it does start to go wrong, the speeds involved are a lot higher and require faster responses. As a driver moves towards the edge of the envelope, the room for error becomes less and less and any change in the external conditions can take the car outside of the envelope and into trouble. This is why so many accidents occur in the wet and on ice when drivers fail to adapt to the greatly reduced road grip.

There are several solutions to this: the first is to learn how to drive the car and detect the onset of wheel slippage so that correction can be applied. This process requires practice and involves recognising the sensory feedback that is the first sign that the car is approaching the limit. The phrase "driving through the seat of your pants" is a very apt description. The second approach is to fit a traction control system where a microprocessor does some of the thinking for you.

In my case, I wanted to use traction control to help tame the 390SE that I sprint. It was extremely susceptible to tail slides last year and at one sprint in very wet weather, it would spin its wheels so much that it would take nearly 5 seconds to travel the first 60 feet. Although the car was being modified to improve the suspension, the engine was being upgraded to give even more torque and power. As a result, I was interested in fitting traction control to help me control the car, especially in wet and slippery conditions.

The system that I had fitted to the car is the Racelogic system which has gained a very good reputation as being state of the art. The demonstration was certainly impressive. It turned a 300 +bhp Supra that would brake traction at 5-10 mph into a controllable car. Without it, the power had to be carefully fed in to prevent a tail slide. Care had to be taken that the car was in a straight line before power was applied on corners. With it, the traction control took over if you overstepped the mark with the throttle. This does take getting used to and I found that I was instinctively lifting off and applying opposite lock despite the fact that I was in the passenger seat!

The system is used on Rolls Royce and Aston Martin cars as well as many competition cars. The system uses a sensor on each wheel to detect the wheel motion and these inputs are fed to a microprocessor that determines when the wheels start to slip. When the slippage exceeds a pre-determined value, the controller cuts the engine power by switching of a fuel injector or preventing a spark. The engine effectively misfires on a cylinder and the power is reduced so preventing any more slippage and keeping the car on the point of maximum traction. The controller is intelligent and cycles through the cylinders so that the misfire and power reduction is distributed. For cars fitted with catalytic converters, the fuel injectors are switched off so that there is no unburnt fuel to go through the exhaust and cause problems with the catalytic converter. With non-cat cars like my 390SE, there is the option of controlling the spark instead. The original plan was to use this, but in the end, we went for the fuel injector cutoff method instead as the Lucas distributor has an intelligent variable dwell control ignition module that detected the traction control and then shut down!

Fitting

The system typically uses the ABS sensor on each wheel but as TVRs do not have ABS, four sensors have to be fitted to detect the wheel motion. The first challenge was to work out how to fit the sensors especially as the 390SE has inboard brakes! Dave Wallis of Tower View Race Service to the rescue. Armed with a variety of brackets and sensor plates, he fitted the sensors to the wheels and wired the cables back into the car. He has worked out how this can be done for the virtually any TVR as well as the Wedges.

The next stage is to get the electronics fitted. The system comprises of a small wiring loom, a controller box, a dashboard control and the optional spark control box. These were mounted under the dashboard and in the driver's footwell. The dashboard control was mounted in the central console where I could at get it when strapped into the car. The control allows the degree of control to be adjusted and also has the all important launch control button. The system also has a data logging facility and a serial connection is provided to plug into the onboard data logging PC. This gives detailed analysis of what is happening to the wheels and the car when driven. It can even detect when wheels lift off the ground!

The variable control is an important feature. Many standard traction control systems err on the safety side and will prevent any wheel slippage at all. This can prevent experienced drivers from driving the car in the way they want. At one sprint, on frustrated competitor was seen with a mobile phone in one hand talking to Ford about ways that the traction control could be disabled on a Puma. Every time he started to push the car, it kicked in and slowed him down. The variable control allows the driver to select the amount of intervention that is required. It can even be switched off. In practice, this could almost be described as a tail slide control. The less intervention, the more the tail would slide and the more correction the driver would need to provide.

So what is it like?

In a word... wonderful! Fortunately, it started to rain heavily just as the installation was finished so it provided just the sort of conditions that all drivers dread — wet greasy roads! The 390 is very twitchy in the wet due to its stiffened and lowered suspension if too much power is applied. However with the traction control enabled in the wet mode, it was like driving in the dry. Despite many attempts to get the back to move, it wouldn’t. It might twitch but the fear inducing oversteer had gone. The power adjustment was difficult to notice and was extremely smooth. Going through puddles and standing water was equally impressive. The tests also proved what I had suspected for some time that the back wheels spin on every gear change which also explains that it is quite twitchy when changing gear.

The next day, I took the car down to Lydden for a test day. I was not sure how much or how little the car would benefit from traction control in the dry but I soon found out on the first lap where part of the circuit was extremely damp. Although I was gingerly going round, the car started to move but the difference was that the movement was damped and a quick flick of the opposite lock and the slide was brought under control. The system had started to act immediately the slide had started and this has slowed the slide and given me time to correct it. This was also true when a car dropped some oil on the circuit. The car started to slide, the traction control damped it down and I finished the rest. It is like have a safety net which helps you if you get it slightly wrong. The end result is that you feel more confident and to quote a well known advert, “it takes the drama out of a crisis”. You also learn exactly where the limits are and this enables you to improve your driving skills.

The data logging facility is also superb and can help diagnose both transmission, braking and suspension problems. It can display the individual wheel speeds and engine revs along with the level of traction control that came in. In this way you can see how much or how little help the Racelogic system provided. It has a compare facility so that you can compare different runs or laps to see if the different line or using a different gear is an advantage. This level of feedback is essential in helping you work out how to get that better time and to see how the car is performing.

Summary

The system is simply amazing and great fun. Although I am using it in a motor sport application, it does have many other applications for road cars. Although it is not a complete cure for spinning and tail slide as they can be caused by other factors than too much power, it does tame the car so that you can accelerate away without the fear of losing the tail. Although you cannot go steaming into a corner too fast and expect it to magically spirit you round as the laws of physics and motion still have to be obeyed, it does provide a safety margin that would not necessarily be there.

For the inexperienced this means being able to drive the car without the fear of losing it. Put the car on the "wet" setting and the car is more docile, more manageable. Whether this could go as far as saving marriages and relationships, I am not sure but it does mean that inexperienced drivers can enjoy a TVR with less fear and foreboding. For experienced drivers, it can help them get on the edge with a larger safety margin. It can be turned off if needed or just reduced in effect. From a competitive view, it does help enable me to drive the car quicker, especially when conditions are slippery or changing. For all drivers, it is a big, big help in wet and icy weather where it seems to be that just breathing on the throttle will cause a tail slide.

Racelogic's traction control should not be seen as a replacement for good driving skills or for getting lines and corners right, but as a method of controlling power induced wheel spins and tail slides in conditions where you need to have a level of driver control that you can only aspire to, it is almost unbeatable. Add to that the data logging facility and it is definitely worth considering. Highly recommended.