ANTI-LAG | How it Works

ANTI-LAG | How it Works

(tires squealing and exhaust cracking) – Huh, what, is it broken? (engines spraying and cracking) Huh! (exhaust cracking) Oh, don't worry it's just anti-lag. (electronic music) Turbos, what's not to like? Oh yeah, lag.
– [Man] You suck. – How do you get rid of lag? Anti-lag. (engine revving and exhaust cracking) If you watched how turbos work, you know that it takes a little while for a car's exhaust gases
to spool up the turbo and make that sweet, sweet boost. If you haven't watched it,
what I'm about to talk about will make a lot more sense if you do. The bigger the turbo, the more
rotational inertia it has, so the longer it takes to spool up. – [Man] You suck.
– So the greater the lag. (screaming) One way to reduce lag is with more turbos, but sometimes twin or sequential turbos still got a lot of lag
and a lot isn't good. – [Audience] Yeah. – Especially if you're
rally racing or drifting, you need that throttle response right now. Anti-lag, also called a bang-bang system, keeps the turbo constantly spooled up, even when you let off the gas and it makes awesome firework sound, (fireworks cracking) and it shoots fire from the exhaust, (engine revving and exhaust cracking) all so you can go faster. It does all of that by
igniting extra air and fuel in the exhaust manifold
or turbine housing, instead of in the cylinder and as we saw in the turbo video, the exhaust side of the housing,
well, that's the hot side. Anti-lag systems rely on that extreme heat to cause gas to spontaneously
combust when it gets in there. That extra boom makes more heat. It also increases the pressure
in the exhaust manifold which keeps the turbine wheel spinning, even when the throttles closed and the exhaust isn't flowing much, so when you go back to the gas pedal, that sweet, sweet boost, well, it's already there waiting for you, like Ryan Gosling in The Notebook. – It wasn't over, it still isn't over. (sighs) – This little trick works really well but as you might expect, it's super rough on all your equipment. That extra heat and all those explosions put a ton of stress on
the exhaust manifold and on the turbo. It's so destructive that
world rally championship cars get a new turbo after every race. That's not cheap. And that is why stock
turbocharged street cars don't come with anti-lag systems. Your warranty would be like,
I don't know, 10 miles, but it would be pretty cool. I'm looking at you OEMs. But if you're determined to blow up gas in your exhaust manifold, well, then there's a couple
different ways to do it. One is called a throttle kick or throttle bypass anti-lag system, which is where the throttle
plates stay slightly open, even when you're off the gas and that's combined with an ECU tune that delays the ignition timing and adjusts the air-fuel
ratio to be a much richer mix. On a typical combustion stroke, the ECU tells the spark plug to fire when the piston is right
around top dead center, so you get the most efficient
fuel burn and the most power, but with delayed ignition,
the spark plug fires when the piston's already on the way down, as late as it possibly can and still keep the engine running. As it begins it's exhaust stroke, the extra fuel hasn't
fully burned off yet, so the whole exploding mixture gets pushed out into the exhaust manifold. It gets stuck out there, still combusting and exploding
right off into the turbo keeping it 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 cracking the
throttle plate open a bit, this methods adds extra plumbing
before the throttle plate to divert air around the
engine when it's off throttle and send it directly to
the exhaust manifold. A bypass valve and solenoid precisely control the flow of air while the ECU provides
the rich fuel mixture and when everything arrives
at the rendezvous point, just before the turbo, bang bang! (exhaust cracking) The turbo spins and you get anti-lag. (children cheering) Modern rally-style systems
have a control knob for multiple settings on
anti-lag aggressiveness, so drivers can get just the right amount of throttle response,
depending on the terrain. It can also be switched off completely to stop the explode-y wear and tear on the expensive turbo parts. Drag racers on the other hand might also have a two-step rev limiter, which isn't actually an anti-lag system but it does make very similar sounds. A two-step rev limiter,
just what it sounds like. It's got two different rev limits. The first one is usually quite
a bit lower than the redline and you probably know
it by it's common name, launch control.
(engine revving) In cars with a lot of power,
you don't need or want to rev all the way to the engine's redline to get the fastest launch. The first rev limit is set to minimize wheel spin off the line and
give you the optimal traction. The second rev limit is, of course, at the top of your red range to prevent you from floating a valve or blowing a hole in your block. Two-step rev limiters often get confused with anti-lag systems because they can both be done
with delayed ignition timing. Firing the spark plugs later effectively limits the
engine's ability to rev but as we just found out, it also pushes unburned
fuels out of the cylinders and into the exhaust
manifold where it goes… (exhaust cracking) If you're car happens to have a turbo, yeah, it might spin up a bit, but not like the systems
designed for anti-lag. So two-step and anti-lag are different, (claps) but they're both still awesome. No lag!
(children cheering) Guys, thanks so much, honestly
we can't do this without you. Make sure you click on
this subscribe button. We got new merch coming out. Sign up on our email
list at Check out this Science
Garage episode on turbos. Cop cars, check out this Wheelhouse. Follow donut on Twitter
and Instagram Follow me @bidsbarto. Don't tell my wife an anti-lag system voids the warranty on our Focus. (light music)


  1. No lag, is better than anti-lag…pre-spool Anyone? Throttle stays open then , wait a min, if there was a third member on a turbo, say a pre electric spool up, there would be no lag ⛽🎈🎇🎭🏐🏎️

  2. "What's not to like?"
    Programmable PCM, bigger injectors, tuning, detonation, worrying about when your turbo is gonna go dry and roast like a marshmallow. Yeah… love em.

  3. Why don't they just build a half electric turbo and feed the electric from the battery, this could start the turbine off from nothing and stop the lag instead of wasting more fuel damaging the turbo in the method you just shown use.

  4. Now amd has it on their graphics card. It's comparatively cheap, you just need to download drivers and buy a 429$ card. Ez

  5. What happened to science garage? How come these episodes dont show up anymore on doughnut media. Bart is one of my favs. Smh anyone know ??

  6. Turbo: you're not fun
    Supercharge: you're llaaaagggyyyyyyy
    Turbo: we have anti lag system
    Supercharge: oh shit

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