History and Development of Anti-Lag Systems (ALS)
Anti-lag systems (ALS) are primarily used in turbocharged engines to reduce or eliminate turbo lag. Turbo lag refers to the delay between the time the driver presses the accelerator and the moment the turbocharger produces enough boost pressure to increase engine power. ALS is commonly associated with motorsports but has also found its way into road vehicles. The development of ALS was driven by the need for more immediate throttle response, especially in competitive racing environments.
1. Origins in Motorsports (1980s-1990s)
The history of anti-lag systems begins in the late 1980s and early 1990s, mainly in Group B rally racing. The turbocharged engines in rally cars provided significant power, but they suffered from turbo lag, making them harder to control in the tight, twisty, and frequently changing terrain of rally stages. This was especially problematic in races like the World Rally Championship (WRC), where instant power delivery was critical.
Key developments:
- Group B Rally Cars (1980s): Manufacturers like Audi (with the Quattro S1) began exploring ways to improve throttle response by experimenting with early anti-lag techniques.
- Toyota Team Europe (early 1990s): Toyota introduced a more refined version of anti-lag in the Celica GT-Four ST185 used in WRC. Their system became one of the first widely recognized implementations of ALS in rallying.
- Ford and Subaru: Other manufacturers like Ford and Subaru followed suit, developing systems to keep the turbo spooled between throttle inputs. The Subaru Impreza WRX and Ford Escort RS Cosworth became famous for their use of ALS.
2. How Anti-Lag Works
Anti-lag systems work by maintaining high exhaust gas flow even when the throttle is closed or only partially open, keeping the turbocharger spinning and ready to produce boost when needed. There are several ways this can be achieved:
- Fuel and ignition manipulation: Retarding the ignition timing and introducing extra fuel causes combustion to occur late in the exhaust cycle, generating exhaust gases that continue to spin the turbo. This method is the most common in modern ALS systems.
- Bypass valves: In some systems, a bypass valve allows air to flow around the throttle plate, creating a continuous exhaust flow even when the throttle is closed.
- Exhaust gas recirculation (EGR): Certain setups use a form of EGR to maintain pressure in the turbo without causing damage to the turbine.
3. Advancements and Mainstream Usage (1990s-2000s)
As ALS technology improved, it spread beyond rallying to other forms of motorsport, including Formula 1 (before the turbo era ended in 1988) and endurance racing. Although ALS was originally developed for competition, it slowly made its way into production vehicles, especially high-performance road cars and aftermarket tuning.
Key developments in the 1990s:
- WRC dominance: Subaru’s and Mitsubishi’s success in WRC with the Impreza WRX and the Lancer Evolution showed the potential of ALS, making the distinctive popping sound of anti-lag familiar to motorsport fans.
- Motorsport regulations: By the late 1990s, anti-lag systems had become so effective that governing bodies in rallying began regulating them to limit the advantages they provided. This led to manufacturers constantly evolving their systems within regulatory boundaries.
2000s:
- Aftermarket tuning: The popularity of performance cars like the Mitsubishi Evo and Subaru Impreza WRX/STI sparked a wave of ALS development in the tuning scene. Many tuners began adapting motorsport-style ALS systems for street use, though these were often less aggressive than race versions to avoid damaging engine components (like the turbo, exhaust manifold, or valves) from the extreme heat generated by ALS.
- More refined systems: Car manufacturers, particularly those involved in rally and high-performance street cars, began integrating less harsh, more reliable ALS systems in production models. Though not as aggressive as racing systems, they provided drivers with better throttle response and a more dynamic driving experience.
4. Anti-Lag in Modern Motorsport (2010s-Present)
ALS continues to evolve, particularly in rally racing. In WRC, modern ALS systems are far more sophisticated, using advanced electronics and ECU tuning to optimize performance without the same level of wear and tear on engines that earlier systems experienced.
- Turbocharging resurgence in F1 (2014-Present): When Formula 1 reintroduced turbocharged engines in 2014 with the V6 hybrid power units, anti-lag techniques were adapted for the new hybrid turbo era. Although these systems are not exactly the same as traditional rally ALS, the energy recovery systems (ERS) in modern F1 cars use similar principles to reduce turbo lag, providing instant power when needed.
- Drift racing: Anti-lag has also been adopted in drift racing, where instant power delivery helps maintain tire spin and control. Cars like the Toyota Supra and Nissan Silvia, popular in drift competitions, often utilize ALS setups.
5. Road Cars and Civilian Use
While aggressive ALS systems are impractical for everyday driving due to their tendency to cause excessive heat and wear on components, milder versions of ALS are integrated into some high-performance road cars, such as the Nissan GT-R and Porsche 911 Turbo. These systems typically focus on maintaining turbo speed during gear changes or short throttle closures to improve acceleration.
6. Challenges and Trade-offs
Though anti-lag offers significant performance benefits, it comes with a few notable downsides, especially in its more aggressive forms:
- Heat generation: ALS significantly increases exhaust gas temperatures, which can damage components like the turbo, exhaust manifold, and valves if not properly managed.
- Increased wear and tear: The extreme pressures and temperatures involved in ALS operation cause increased stress on engine components, requiring more frequent maintenance.
- Fuel consumption: ALS burns additional fuel to maintain turbo speed, which can make it less efficient, although this has been less of a concern in motorsports than in civilian applications.
7. Future of Anti-Lag Systems
The future of anti-lag technology will likely focus on improving reliability and reducing the downsides of increased heat and wear. With the rise of hybrid and electric turbo systems, engineers may find new ways to reduce lag without relying on traditional ALS methods. Electric turbos, which spin up almost instantly using electric motors, are already in development and may ultimately replace conventional ALS systems. For example, some high-end models like the Audi SQ7 TDI already use electric compressors to eliminate lag.
In summary, anti-lag technology has evolved from its early beginnings in motorsport to a highly refined system that continues to play a crucial role in improving turbocharged engine performance. As vehicle technology advances, particularly with the rise of electric and hybrid propulsion, the future of anti-lag systems may shift away from combustion-based methods to more advanced, electric-assisted solutions.