What is it, how does it work and do I need it?
A proper launch is key to success in any level racing. Eliminating wheel spin and wheel hop, maximizing traction, weight transfer and power off the line, and in forced induction car, to build boost before launch are all critical components in the launch of any vehicle. The ability to do all of these consistently and in a controlled fashion with as little impact to the vehicle as practical is key to success in any level of racing. Sophisticated traction control systems can aid in the traction and wheel spin areas, but work by limiting your power. This can seem counterintuitive when you “want to go fast.” In addition, true traction control systems sophisticated enough for racing applications are available only in a handful of exotic cars with a price tag much out of the traditional “tuners” budget. The solution for all of these problems, however, is quite simple: Launch Control.
What is launch control, and how does it work?
Launch control (sometimes known as a stutter-box or 2 step rev limiter) are fairly simple, yet effective in ensuring consistent reliable launches at the track, strip or even on the street. The user defines a “launch rpm” that, when launch control is activated, the vehicle will maintain. This allows the user to hold the car at full throttle while still maintaining a suitable RPM for launch, based on vehicle capabilities, traction, wheel hop, etc. Turbocharged cars see an additional benefit in the ability to build boost before the vehicle leaves the line. These capabilities lead to smoother, consistent and reliable launches with maximum power from the moment you leave the line. This will help lower your 60ft times and/or help you be the first into the corner.
In turbocharged vehicles, additional boost can be gained using Gizzmo Electronics LI2 ignition retard feature. Retarding the ignition from the default setting increases load, which in turn will cause the turbo to spool, thus creating more boost for launch. Each vehicle will have unique requirements to achieve maximum, yet safe, consistent and reliable power during a launch event. The ability to control the amount of timing retard only when launch control is activated allows the user to custom program the LI2 to their particular vehicle setup and requirements. When adjusting these parameters it is also suggested that Exhaust Gas Temperatures are monitored to ensure EGT levels remain in a safe range as retarding ignition can increase EGTs in such conditions.
Note that launch control is not to be confused with Anti-lag, which is another method to aid in launch and off throttle boost. Anti-lag essentially creates an explosion inside the turbo to maintain boost, even when the driver is off throttle or at a stop. Anti-lag is commonly used on rally cars and other turbo-charged race cars. It is VERY hard on the turbo and should not be run by anyone with a budget less than that of a race team as it will lead to premature failure of your turbocharger. Sometimes these terms are used interchangeably – however typically Anti-Lag Systems refer to a system that functions AT SPEED (i.e. while the vehicle is in motion and in gear) with the throttle closed. This is sometime refereed to as Rally-Anti-Lag, due to it’s common use in Rally Racing vehicles. The intention is to keep boost pressure even when the drive is off throttle while cornering, etc.
An anti-lag system will retard timing, bypass the throttle plate (i.e. injector more air into the exhaust stream, creating a VERY lean mixture) and sometimes will influence fueling. The idea is to create a lean, dense mixture in the exhaust stream and keep the turbo spooled at all times. As the mixture is so lean, it will ignite in the turbo/exhaust stream. This is much more violent than that of WOT style launch control and hence the additional danger to turbos and other vehicle components. Creating boost with the throttle closed also poses additional threats to the turbo due to the additional pressure on the compressor housing (think surge!) Many turbo manufacturers will not warranty damage caused due to use of this Rally-Style Anti-Lag system. As mentioned in the article, unless you have the budget of a rally team, or a large supply of turbos, it is NOT recommended to use Rally Style Anti-Lag for street vehicles.
Hopefully this clarifies the difference between the two systems and terms which are commonly interchanged. For the purpose of all my articles, unless otherwise specified, “Anti-Lag” will refer to at speed Rally style ALS and Launch-Control to WOT Standstill/Shifting boosting systems.
Launch control units work by intentionally creating a misfire event in random cylinders when launch control is activated (commonly activated through the use of a clutch switch and/or speed sensor signal.) The launch control interface intercepts the spark trigger from the ECU (note this is NOT the high voltage spark signal!) and modifies/interrupts the signal to create the misfire event to hold the vehicle at the desired launch rpm. In a turbo application, having the throttle open while inducing misfire will increase the velocity and density of exhaust gases, which will lead to turbo spool and generating boost with load. This results in boost being generated before launching and therefore allowing a vehicle to launch with considerably more power. In addition to control at launch, controllers which use a clutch activated reed switch, such as the Gizzmo Launch Interface, also can serve as a controller for flat shifting (no lift to shift) where the driver keeps the accelerator floored during a shift and simply presses the clutch to activate the second stage rev limiter. Similar to a launch event, this will cut ignition and timing to the desired rpm, preventing over-revving during the shift event. This allows the user to make quicker shifts and maintain boost while shifting.
Do I need it?
- Do you want consistent launches, without wheel spin or wheel hop in your boosted or naturally aspirated car?
- Do you have a boosted car and wish to build boost before you leave the line for more powerful launches?
- Do you want every advantage you can get to win races, run better times and/or just get the most out of your vehicle?
If so, then a launch control interface may be a serious consideration for your vehicle.
Keep in mind that the harder you launch the vehicle, the more stress you will put on your drivetrain. Axles, driveshaft, clutche, etc must all be capable of transferring the power you’re now applying to the wheels. With sticky tires such as drag radials, these forces are only magnified. Before launching your vehicle aggressively you will want to make certain that all these components are capable of handling the higher loads.
NOTE: in some vehicles an aftermarket launch interface may not be compatible with the ignition system in all cars. Vehicles which use a “smart” off board igniter where the ECU communicates with the igniter (rather than just triggers a spark) may not function properly, since the launch interfaces interrupts this signal. In addition, cars with misfire detection as a hard fault, or where the ECU receives a receipt of the spark. A little research into your vehicles ignition system and coil setup will determine if launch control is possible with your vehicle.
This article appeared in Juiced Custom Automotive Magazine, Issue #4 May 2011
Copyright © Brian Barnhill 2011
Cannot be used or reprinted without permission.