(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.
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Don't tell my wife an anti-lag system
voids the warranty on our Focus.
(light music)