Have you heard of the anti-lag system before? It is also called "ALS" or the bang-bang system. This closes the turbo lag of the engine. For example, if you approach a curve and have to brake so as not to fall victim to the centrifugal force, the turbocharger loses its speed and has almost no power in a certain speed range. When several curves follow one another closely, you drive for a long time without a turbo boost. When accelerating, the turbocharger needs a few milliseconds to get up to speed so that it can again develop its performance-enhancing effect. The turbo also loses its pressure during the shifting process.
the anti-lag system
To avoid this brief loss of power, i.e. the turbo lag, the turbocharger is kept at a high speed with a trick. For this purpose, the turbo air bypasses practically the entire engine with the help of a valve. The air coming from the turbocharger is branched off in front of the closed throttle valve and is fed back directly in front of the engine valves. The actual combustion chamber is bypassed, which is why the term automatic air recirculation system is sometimes used. Back on the way to the turbocharger, the air is deliberately enriched with petrol. If necessary, you can adjust the engine so that the mixture becomes richer. The gas-air mixture ignites on the hot manifold and explodes. Because of these explosion noises, the name Bang-Bang came into being, the crackling in front of the bends, which is known from rallying. The high pressure generated by these explosions brings the turbo wheel up to high speed, even though no further power is required at this moment.
Retrofit the anti-lag system
In racing, it actually makes sense if milliseconds decide about victory and it does not matter how long the engine lasts. Due to the constant explosions in front of the turbo wheel, its lifespan is rapidly declining. And of course we also have the valves, in which direction the pressure of the ignited gas also unfolds. The valves burn faster than in normal operation. The manifold is also exposed to a very high load and will tear sooner or later if you use the system constantly. The speed of the engine and turbocharger do not match. The temperature distribution changes, the load on the engine goes far beyond its limit. Some vehicles have an electrically operated turbocharger. No valve needs to be installed on these models. The turbo lag can be eliminated by intervening in the engine control. But here, too, the concerns about material stress apply to the relatively small benefit.
Conclusion on the anti-lag system on the road
If you want to drive your engine longer, you should stay away. Even if the engine sounds tempting like a rally car, the increase in performance / effectiveness through an anti-lag system is minimal and not recommended for private users. The ALS is suitable to let the boost pressure drop only very slightly during the switching process. The ignition angle is pulled very late and fuel continues to be injected even with the throttle valve closed. The effect is cool, because with a late ignition angle, the combustion moves more and more towards the opening time of the exhaust valve and at some point the flame front of the combustion can even be seen on the tailpipe of the exhaust, but that is not good in the long run.
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