ANTI-LAG | How it Works

(tire screeching and exhaust crackling) - What's broken? (engines squirting and creaking) Hey! (escape count) Oh, don't worry, it's just anti-lag. (electronic music) Turbos, what don't you like? Oh yes, delay. - You suck. - How do you get rid of the delay? Anti-lag. (engine revving and exhaust crackling) If you've seen how turbos work, you know that it takes a while for a car's exhaust to rev up the turbo and create that sweet, sweet boost. If you haven't seen it, what I'm about to talk about will make a lot more sense if you do. The larger the turbo, the more rotational inertia it has, so the longer it takes to run. - You suck. - So the longer the delay. (Screaming) One way to reduce lag is with more turbos, but sometimes dual or sequential turbos still have a lot of lag and many of them are not good. - Yes. - Especially if you're into rally racing or drifting, you need that throttle response now.

The anti-lag, also called the bang-bang system, keeps the turbo constantly confused even when you release the accelerator and makes a big fire

works

sound (the fire

works

crackle) and shoots fire from the exhaust (the engine revs and the exhaust crackle). ) all so you can go faster. It does all of that by igniting extra air and fuel into the exhaust manifold or turbine housing, rather than the cylinder, and as we saw in the turbo video, the exhaust side of the housing, well, that's it. the hot side. Anti-lag systems rely on that extreme heat to cause the gas to spontaneously combust as it enters.

That extra boom provides more heat. It also increases pressure in the exhaust manifold, which keeps the turbine wheel turning even if the throttles were closed and the exhaust isn't flowing much, so when you get back on the throttle, that sweet, sweet boost, well, it's already there. . waiting for you, like Ryan Gosling in The Notebook. - It's not over yet, it's not over yet. (Sigh) - This little trick works great, but as you might expect, it's very hard on your entire team. That extra heat and all those explosions put a lot of pressure on the exhaust manifold and turbo.

It's so destructive that world championships get a new turbo after every race. That's not cheap. And that's why stock trams with turbos don't come with anti-lag systems. Their warranty would be like, I don't know, 10 miles, but that would be cool. I'm looking at your OEMs. But if you're set on injecting gasoline into the exhaust manifold, there are a few different ways to do it. One is called the throttle bypass anti-lag system, which is where the throttle plates remain slightly open even when the accelerator is not being pressed and which is combined with an ECU tune that retards ignition timing and adjusts the ratio. air-fuel to be a much richer mixture.

In a typical combustion stroke, the ECU tells the spark plug to fire when the piston is properly seated around top dead center, resulting in the most efficient fuel burn and the most power, but with delayed ignition. , the spark plug fires when the piston is already on the way down, as late as possible and still keep the engine running. When it begins its exhaust, the extra fuel is not completely burned, so the entire explosive mixture is pushed into the exhaust manifold. It stalls, still burns, and explodes right into the turbo, keeping you spooled up and giving you all those anti-lag benefits.

Another type of anti-lag system is called rally style or secondary air injection, which is what you usually see on WRC cars. Instead of opening the throttle valve slightly, this method adds additional piping to the throttle plate to allow air to flow around the engine when it is out of gas and send it directly to the exhaust manifold. A bypass valve and solenoid precisely regulate airflow while the ECU maintains the rich fuel mixture, and when everything hits the meeting point just before the turbo, bang bang! (exhaust bead) The turbo spins and you get anti-lag. (kids applauding) Modern rally-style systems have one control knob for multiple anti-lag aggressiveness settings, so drivers can get just the right amount of throttle response depending on the terrain.

It can also be turned off completely to stop blowout wear on expensive turbo parts. On the other hand, drag racers can also have a two-stage rev limiter, which is not actually an anti-lag system but makes very similar sounds. A two-stage rev limiter, exactly what it sounds like. It has two different rev limits. The first is usually a little lower than the red line and you probably know it's common name, launch control. (engine revving) On high horsepower cars, you don't need or want to go all the way back to the engine's redline to get the quickest launch.

The first rev limit is set to minimize off-line wheel spin and give you optimal traction. The second rev limit is, of course, at the top of the red range to avoid actuating a valve or putting a hole in the block. Two-stage rev limiters are often confused with anti-lag systems because both can operate with delayed ignition timing. Firing the spark plugs later effectively limits the engine's ability to accelerate, but as we just discovered, it also pushes unburned burns out of the cylinders and into the exhaust manifold where it goes... (exhaust bead) If your car has turbo Yes, it can spin a little, but not like systems designed for anti-lag.

So two-step and anti-lag are different (applause), but they're both still great. Without delay! (children applauding) Guys, thank you very much, honestly, we can't do this without you. Be sure to click this subscribe button. We have new merchandising coming out. Sign up for our email list at shop.donut.media. Check out this episode of Science Garage about turbos. Police cars, look at this wheelhouse. Follow donut on Twitter and Instagram @donut.media. Follow me @bidsbarto. Telling my wife that there is no anti-lag system will void the warranty on our Focus. (light music)