Launch control is an electronic driver aid that's designed to help a driver achieve consistent, quick and more easily controlled standing starts.
These systems, which are triggered by a series of activating steps, typically take control of several key criteria - such as engine speed - in order to minimise driver workload. Consequently, a driver using launch control can make easy and rapid getaways without the degree of precise control that would otherwise be required.
Such systems are available in cars with both manual and automatic transmissions, including dual-clutch types. Numerous manufacturers offer cars with launch control, including BMW, Nissan, Porsche and Audi, and even conventional hatches and saloons are available with launch control - which is often the result of increased commonality throughout model ranges.
How does launch control work?
In order to get a car with a manual transmission off the line as quickly as possible, without assistance, a driver has to carefully judge the launch rpm and clutch actuation. Launch at too low an rpm and the engine may bog, resulting in miserly acceleration; launch too aggressively and the wheels may spin, again harming acceleration.
Similarly, getting the clutch actuation wrong during a launch can result in a stall or excessive wear to the clutch - while particularly violent clutch control could even result in damage to the drivetrain. Correctly modulating the clutch and the throttle at the same time, however, can prove difficult for some drivers.
A launch control system alleviates this problem by regulating the engine's output to deliver maximum thrust in an automatic, controlled fashion without exceeding the available traction in an overwhelming way. This removes the requirement of the driver to balance both the accelerator and the clutch, resulting in more consistent standing starts.
The sequence for arming launch control varies from manufacturer to manufacturer but, typically, in a manual car the driver will have to activate the system, push the clutch pedal and then engage first gear.
The accelerator is then pressed and held to the floor, at which point the system will bring the engine to a predetermined optimum rpm for launching - and hold it there. The driver then releases the clutch pedal rapidly and the car accelerates as hard as possible, with the launch control system modulating the engine's output to deliver maximum acceleration without harmful amounts of wheelspin.
Some systems allow the driver to calibrate the launch rpm, too, in order to better tailor the car's behaviour to the weather and surface conditions. For example, a driver may want to dial the launch speed back by a few hundred rpm if the surface is proving somewhat slick; if the car is hooking up well, however, then a few extra hundred rpm on the launch might make all the difference.
Using launch control in an automatic car, once the system has been engaged, typically involves standing on the brake then pinning the accelerator to the floor. The engine will be brought up to the target speed and, when the brake pedal is released, the car will launch; during this process, the car's electronics may alter the behaviour of the transmission - such as more rapidly engaging and disengaging the clutches in a dual-clutch transmission.
Even though the event is over in a matter of seconds, much is done by the launch control system in the time it is active. The launch control system in a Camaro ZL1, for example, will adjust the engine's torque output 100 times per second in order to maximise acceleration. A launch control system may, like a traction control system, use the brakes at the driven wheels - or active differentials - to shift torque to the tyre with most traction in order to improve acceleration even more.
How does launch control differ from traction control?
A traction control system will do everything in its power to prevent wheelspin, in order to keep the driver safe and in control of their vehicle. Stand on the accelerator from a dead stop and traction control will quickly step in, reducing torque to help stabilise the car. This gives you a hassle-free step off the line but often causes substantial reductions in engine output, resulting in sluggish acceleration.
Launch control systems, on the on the other hand, are designed solely to deliver maximum acceleration from a stop - and activating the system lets the car know exactly what the driver intends to do. Unlike a traction control system, which aims to eliminate wheelspin, a launch control system will instead aim to keep the engine at or above a specific speed to grant maximum acceleration.
To do this, the launch control system often permits a modicum of slip at the driven wheels to avoid bogging the engine; watch slow-motion footage of cars launching and you'll often see them spinning their driven wheels as the launch control system works to keep the engine on song - striking a delicate and automated balance between traction, slip and engine output to deliver the quickest standing starts.