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ESP Explained

ESP Explained

What is ESP in a car?

Electronic Stability Programme (ESP) is a computerized safety technology present in most modern cars. It is designed to improve a vehicle’s stability by detecting and reducing loss of traction, thus preventing the tyres from skidding uncontrollably. When the stability control programme detects a loss of steering control, it automatically applies individual brakes to help ‘steer’ the vehicle where the driver intended it to go.

The ESP system fitted to the majority of modern cars is manufactured by Bosch. Car manufacturers then fine-tune the standard settings to best suit the handling properties and sporting credentials of their particular cars. Many car manufacturers have also adapted and created their own versions of ESP which is discussed in the section below. 

ESP Warning Lights

ESP or ESC? What is the Difference?

To all intents and purposes, Electronic Stability Programme (ESP) and Electronic Stability Control (ESC) are actually one and the same; the differences in their name resulting from the vehicle manufacturer you choose to buy from. Other, branded, stability control systems are variously named “DSC” (i.e. Aston Martin, BMW & Jaguar), “MSP” (Maserati), “PSM” (Porsche), “CST” (previous generation Ferrari) and many more. 

How Important is ESP in a Car?

In short, very important. Statistics in the UK have shown that ESP can reduce the chance of drivers being in a fatal accident by 25%. Similarly, studies in Sweden show up to 32% less chance of fatal accidents occurring in bad weather when the car is equipped with ESP.

Until you’ve actually driven a car with and without ESP, beyond grip limits on a test track and had the opportunity to compare the difference, it’s quite difficult to truly understand the importance of this quite remarkable system. 

It is important to note that not all cars are fitted with ESP. It was only from 2014 that the European Union made it mandatory that all (mainstream) cars have ESP installed. Even so, low volume sports cars, such as the Ariel Atom and Caterham 7, remain exempt from such a requirement.

How Does ESP Work?

ESP operates in conjunction with the Anti-lock Braking System (ABS) and Traction Control System (TCS). ABS is of course designed to maintain traction and enable steering during severe braking by preventing lockup, whereas TCS helps a vehicle’s drive wheels maintain traction during acceleration. Put more simply, ABS stops the wheels from spinning whilst braking and TCS stops the wheels from spinning whilst accelerating.

ESP operates mostly through the ABS, but also relies on TCS to detect subtle differences between the driver’s control inputs and the actual response of the vehicle.

The purpose of ESP is to constantly monitor steering wheel angle in relation to the actual direction of travel; measuring individual wheel speed, yaw angle and steering angle 25 times per second. In doing so, ESP helps compensate for driver errors that would otherwise affect lateral dynamics; whereas ABS and traction control systems do the same for longitudinal dynamics.

If the car loses lateral traction, and either the front or rear starts to slide sideways, ESP reacts by mitigating the cause of the skid; reducing power when appropriate, and applying individual brakes as required to help force the car to follow the steering angle. In the event of understeer, ESP applies the brake to the inside rear wheel to help the car rotate more, whereas if oversteer is the issue ESP triggers the outside front wheel brake to create a more helpful pivot point to bring the rear of the car back under control.

Bosch ESP diagram

Original image source – Bosch 

 

Depending on the vehicle, the ESP ‘umbrella’ can also include numerous other functions to further support safety and control: Electronic Brakeforce Distribution (EBD), brake disc wiping, brake pre-fill and Emergency Brake Assist (EBA) being just a few. Interestingly, many tyre pressure monitoring systems also take their readings through the ESP software to avoid needing a heavy valve assembly within each wheel.

Top Driving Tip

Keep in mind that no matter how advanced the active safety systems fitted are, any car remains subject to the laws of physics and ESP can only respond to steering angle; making it somewhat redundant if you fail to steer where you want to go.

 

ESP Warning Light

When a car is in motion and the ESP warning light comes on, it will show in 1 of 2 ways:

  1.   Steady illumination
  2.   Flashing

 

Steady Illuminated ESP light

Steady illumination of the ESP/ESC warning light (typically a symbol depicting a car with lurid skid lines behind it) indicates that the system is inoperative.  Either it has been switched off deliberately (by the driver, or passenger!), or it may have failed for some reason; most usually a temporary fault, caused by a sensor overheating (in which case, allow things to cool down, then ‘reboot’ the system by switching off the ignition, pausing a little while, then re-starting the engine).

It’s worth noting at this point that some cars automatically either partially or fully disable ESP when certain driving modes are selected.  For example, Race mode in an Alfa Romeo Giulia Quadrifoglio removes ESC completely; whilst Track Mode in Aston Martins and sporty Jaguar models simply backs off the point at which DSC triggers, allowing for some spirited driving and ‘dynamic latitude’ before the electronic safety net deploys.  Always good to fully understand your own car, and how it will behave in different settings and situations.

By default, ESP is always ‘on’ and ready to assist the driver every time the engine is started.  This way, we cannot commence a new journey having forgotten to re-engage ESP.

Should the ESP warning light stay on, even after the reboot suggested above, and after an extended cool-down/reset period (i.e. 30 minutes or so), a visit to your dealer or marque specialist is required, so as to diagnose and fix the problem.  

Flashing ESP light

If the ESP momentarily flashes whilst the vehicle is in motion, it is an indication that the traction control system is intervening. When the car detects at least one of the wheels starting to slip, the ESP kicks in to help you recover your intended path and the light briefly flashes to indicate it has done so. This may be interpreted as a warning to drive with greater finesse, and/or with more attention to grip levels (it stands to reason that ESP triggers readily when driving in extreme conditions such as mud, ice or snow)

In Conclusion

The Electronic Stability Programme is an amazing tool that substantially decreases the probability of an undesirable outcome should the vehicle’s tyres skid uncontrollably. If you’d like to safely test how your car reacts with and without ESP’s support, we thoroughly recommend trialing it in a controlled environment on one of our Dynamic Driving or Total Control courses…

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