What is an anti-lag or misfiring system?

I’m sure some of you have heard of anti-lag systems or sometimes known as misfiring systems, thanks to anime like Initial D. You might have noticed that most of the cars have flames coming out of their exhaust when they shift gears. If you’ve watched Top Gear’s review on the Prodrive P2, you will see that the P2 has it too. That’s a misfiring system in action. Let’s just call it anti-lag from now on. So what does anti-lag do?

First of all, we have to have a quick re-cap on how turbocharging works. Essentially, exhaust gas is used to spin a turbine which compresses intake air. But what happens when you shift gears? You have to lift your foot off the throttle. Exhaust gas velocity drops, and the turbine blades slow down. Intake boost pressure drops. For the next gear, you have to wait until the turbine spins up again for the boost to kick in. This is what you call turbo lag. However, turbo lag should not be confused with boost threshold, which is the minimum engine RPM which is required for the turbine to physically supply boost.

A typical antilag system works when the throttle is closed, which is what happens when you take your foot off the accelerator pedal. An antilag system introduces some unburnt petrol into the exhaust manifold. The heat of the manifold causes the unburnt petrol to combust, and the exhaust gas produced by this combustion keeps the turbine spinning, preventing the blades from slowing down – effectively reducing or eliminating turbo lag.

There are two ways to go about this. An aftermarket anti-lag system like those that come with aftermarket ECUs like MoTeC will adjust ignition timing during closed throttle situations to a point where the exhaust stream becomes really rich with unburnt petrol. This is done by retarding the timing to about 40 degrees after top dead center. Top dead center is the point where the piston is furthest from the crankshaft. Rally cars use a different way of introducing petrol into the exhaust manifold. There are separate injectors that introduce fuel directly into the exhaust manifold. Some of this mixture will continue burning in the turbine and down the exhaust system, resulting in the flames and explosions you hear coming out of the exhaust muffler.

The use of anti-lag greatly reduces the life of a turbocharger and engine because of the extreme heat from the combustion in the exhaust manifolds. This is why it is normally only used in races and rallies and not suitable for street use, as the lifespans will become too impractical. It also increases emmissions and is generally too loud for street use, making it illegal on the road.

Video: Subaru Imprezas showing off their Anti-Lag Systems

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Paul Tan

After dabbling for years in the IT industry, Paul Tan initially began this site as a general blog covering various topics of personal interest. With an increasing number of readers paying rapt attention to the motoring stories, one thing led to another and the rest, as they say, is history.

 

Comments

  • Celicazz (Member) on Jun 29, 2006 at 4:20 am

    hurm…better dont hav it here in Malaysia…if not, a Kancil will be 'shot' forward by this external combustion…haha, joking…

    Like or Dislike: Thumb up 2 Thumb down 0
  • familyman (Member) on Jun 29, 2006 at 4:29 am

    these people sure got money to burn one, during my days of turbo times always thinking of ways to extend the turbo lifetime….

    but one time remember seeing an orange evo on mr2 with flames and bang coming out of the exhaust.. m'sia turbo drivers also rich can install these hehe.

    Like or Dislike: Thumb up 1 Thumb down 0
  • garfield3929 (Member) on Jun 29, 2006 at 4:31 am

    oh the fire at the exhaust is actually misfire thingy, i tot it's a situation where we move to a lower gear n the tyre move the transmission to speed up the engine rev n causes the air-fuel mixture in the cylinder to leave the cumbustion faster which is not fully burnt. then the mixture flowing out the exhaust n burn there…>.

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  • szw (Member) on Jun 29, 2006 at 4:35 am

    dats all ?

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  • Paul Tan on Jun 29, 2006 at 4:37 am

    szw: what were you expecting?

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  • jzkzlz (Member) on Jun 29, 2006 at 4:37 am

    wow…wat a firecrackers show….

    don't these knocking effect spoilt the turbo??

    or will the silencer getting wet with these over injected petrol??

    Sure those engines only have the lifespan of

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  • honda_driver (Member) on Jun 29, 2006 at 4:42 am

    jzkzlz, didnt you read the whole posting? of course an anti-lag system is bad for the turbo, it also damages the exhaust system.. its a favourite for use on rally cars.. Paul has stated it clearly there. please read la the whole thing.. paul spend so much effort to post, and no one bothers to read it.

    actually.. in my opinion, anti-lag is the proper term.. misfiring system is not the proper term, but something that i've only heard used in malaysia.

    most of the cars in malaysia that we see that "seem" to have this system is actually not. There are products you can buy that "simulate" the effect, but is not an actual antilag system. All the high end standalone ECU's have the ability for antilag to be programmed into as an option.

    Like or Dislike: Thumb up 0 Thumb down 0
  • mystvearn (Member) on Jun 29, 2006 at 5:04 am

    not as impressive as prodrive or the batman car :p

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  • aesthari (Member) on Jun 29, 2006 at 6:53 am

    Yup, anti-lag is the correct term. I believe people called it misfiring system because of the burst of flames from the exhaust; that usually happens when a car's engine timing is off, or releasing backpressure, that's why they called it misfiring system, i think :p Not too sure though, just my opinion, no need to quote me on this…

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  • raybrig85 (Member) on Jun 29, 2006 at 7:13 am

    alwiz heard the anti-lag term…misfiring system??jarang kedengaran…btw…thanx paul with the good info…

    hhmm…can c this happen at the f1 cars and super gt…same goes to rally…

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  • Paul Tan on Jun 29, 2006 at 7:16 am

    the term misfiring is usually used in japan, i think.

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  • Tracks (Member) on Jun 29, 2006 at 4:21 pm

    In the Initial D, the black Evo3 has the anti-lag system and they refer to it as the misfiring system. Therefore, Paul I think your are right about the term being use there. I think same goes with Hong Kong.

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  • honda_driver (Member) on Jun 29, 2006 at 4:39 pm

    it could also be an incorrect translation from japanese? who knows.. their words always seems to be translated weirdly from english.

    raybrig, anti lag is only used on turbocharged cars.

    hence the term anti-(turbo)lag. It basically keeps the turbo spooled up off throttle, and when the driver steps on it again, he doesn't need to build up boost again, as the boost is maintained by the system.

    the sound you hear from the super Gt cars is just backfiring from throttle liftoff before a corner. lots of fuel pumped on full throttle, sudden liftoff to brake, and some unburnt fuel goes out and burns up.. its quite normal with race spec engines.

    As for f1 cars, its their traction control, which works by cutting engine power to prevent wheelspin. There are sensors (somewhat like ABS) that detect wheelspin. Why the weird sound? because they use a combination of retarding the engine as well as cutting off the fuel supply to some cylinders. The misfiring sound you hear, is the unburnt fuel from some cylinders igniting as they come into contact with the hot exhaust.

    Like or Dislike: Thumb up 0 Thumb down 0
  • Zgriffin (Member) on Jun 29, 2006 at 4:46 pm

    Racing activities always an expensive hobbies to all Malaysian as most of the high performance gadget are imported.

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  • rexis (Member) on Jun 29, 2006 at 4:57 pm

    awwww, thats misfiring system, i see i see.

    Like or Dislike: Thumb up 1 Thumb down 0
  • raybrig85 (Member) on Jun 29, 2006 at 5:09 pm

    thanx abt the info honda_driver…

    btw…abt the f1 cars…i know the sound of the traction control…and wut ure saying is da truth…but…still u can hear the sound of anti-lag…

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  • Dogster (Member) on Jun 29, 2006 at 5:37 pm

    Where was this held?

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  • Joe v2.0 (Member) on Jun 29, 2006 at 10:24 pm

    one way to reduce this turbo lag prob without using those anti lag system is by using smaller turbine. Smaller turbins are much faster to spool but with the sacrafice of top end power.

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  • honda_driver (Member) on Jun 29, 2006 at 10:29 pm

    the "misfiring" sound is the combination of the engine being retarded, and fuel being cut from some cylinders. And it will only happen, when the systems detects wheelspin. its not "anti-lag". F1 cars today have no turbos mah ;) only a turbo car can get 'lag'.

    anti-lag systems on turbo cars also sound similar, because the engine is being retarded but fuel is still pumped in la.. thats the difference. so you also get a similar 'misfiring' sound.

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  • engtaokia (Member) on Jun 29, 2006 at 10:40 pm

    can make small size party BBQ chicken at the exhaust there :p

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  • raybrig85 (Member) on Jun 29, 2006 at 11:38 pm

    hhmmm..thanx…mbe i was wrong…:)

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  • friendnotfoe (Member) on Jun 30, 2006 at 2:35 am

    for those that you saw on our road most are not this system, just a spark plug attached at the muffler and etc etc… if i'm not mistaken…heard it somewhere…

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  • DAN (Member) on Jun 30, 2006 at 3:13 am

    nice..nice fell a performance!!…wo..u

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  • cbljkkj (Member) on Jun 30, 2006 at 3:35 am

    Using a smaller turbine would not guarantee complete anti-lag if you are thinking bigger turbines have lag. Small turbines do have some lag although very little. Thing is, people tend to upgrade their turbines to a bigger size for more power to showcase in drift or drag.

    The anti-lag is used to help the cars achieve maximum usage of the gears to achieve top speed or the speed that they are looking for. Most of the time, anti-lag is used in competitions to maximise power and efficiency in track times because of the reduction in turbo lag.

    Only the "really anal", rich and stupid or competition people use it.

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  • daze (Member) on Jun 30, 2006 at 6:07 am

    friendnotfoe..that's d flamethrower..

    well. locally. u still can get it done d antilag. as long as u got money wat..

    heard u can turn it on or off.. to prolong ur turbo life span…

    Like or Dislike: Thumb up 0 Thumb down 0
  • Akazamabamaboo (Member) on Jul 13, 2006 at 6:20 pm

    Nice…I'm gonna turbocharge my Kancil and watch the car itself explode…hahaha…

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  • goldcanglam (Member) on Jan 07, 2008 at 3:41 pm

    want to get ur car or bike misfire….no need turbo or big modify on ur car or bike…just need modify few wire …and know the way to “play”…u can go to you tube and watch my honda ex5 misfire…is full original engine without modify…check it out …

    Like or Dislike: Thumb up 0 Thumb down 0
    • deano on Feb 08, 2012 at 7:47 am

      tell me wat wires need to b cut modified etc mait n im on it.safe deano

      Like or Dislike: Thumb up 0 Thumb down 0
  • cokonex on Feb 28, 2009 at 10:43 pm

    I WANA KNOW IF THERE IS A ECU SYSTEM OR A WAY TO USE THE ANTI-LAG SYS. AT WILL

    SO WHEN I'M NOT PLAYING STUPIS I CAN TURN IT OFF

    AND USE IT BESIDE A HOT CHIK!!!

    :-p

    Like or Dislike: Thumb up 0 Thumb down 0
    • fordRStuner on Apr 07, 2010 at 6:56 pm

      ALS systems [because they’re part of the ECU and are electrical] can be switched on and off. Depending on size of the turbo, they can be useless, or almost necesssary. A small turbo such as a T2 or T25[uprated version found on escort cosworth small turbo edition] with uprated/lightened internals will spool up much quicker than with standard internals [much like lightning and knife edging crank, just to eliminate the small amount of resistence.]

      Get a big turbo [something like a T3/ T34/ T4], lighten the internals, THEN have a mild ALS system and you get all the benefits without having to run such agressive ALS that it kills turbo/manifold prematurely.

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  • SR20DE on Apr 10, 2009 at 8:03 am

    cool!!! soo that's what missfiring system is.. thanx ^_^

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  • lawrence Amoako on Mar 27, 2010 at 2:18 am

    i really want to understand surging and stalling?

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  • Nicholas on May 15, 2012 at 7:18 pm

    Naturally Aspired engines, and supercharged engines are extremely better that turbocharged engines. I don’t understand why people jump straight to turbos when it comes to modifying thier japanese shit-box or 300-dollar-commodore. If you spend the effort upgrading and tuning the engine WITHOUT forced-induction, not only will you have a better preforming car, the engine will be far more reliable and will have a longer life.

    This is the reason all those Subaru WRX STi’s (and other similar cars) have terrible low-end torque.

    Like or Dislike: Thumb up 0 Thumb down 2
  • Nicholas on May 15, 2012 at 7:19 pm

    Naturally Aspired engines, and supercharged engines are extremely better that turbocharged engines. I don’t understand why people jump straight to turbos when it comes to modifying thier japanese shit-box or 300-dollar-commodore. If you spend the effort upgrading and tuning the engine WITHOUT forced-induction, not only will you have a better preforming car, the engine will be far more reliable and low end torque

    This is the reason all those Subaru WRX STi’s (and other similar cars) have terrible low-end torque.

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  • Combination of supercharger and turbocharger in one engine unit is the ultimate art, eg: Lancia Delta S4 (long forgotten rally legend). Supercharger provide low rpm torque and turbocharger kicks in during high engine spin.
    Oh god, i miss the Group B golden era of rallying, where some of the most powerful car / technology are developed during that time.

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  • Haarrvin on Jan 21, 2015 at 5:09 pm

    Does cars with double clutch gearbox experience turbo lag?

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