(Anti-Lag System) er det noe og satse på ?

[bige]

How the turbo Anti-Lag System works

 

Bang-bang (also known as ALS which stands for Anti-Lag System) is an engine management technique that allows to minimize the turbo lag time.

 

As you might be aware of, turbochargers display what is known as lag time which is the time needed for the turbine to reach its full throttle from an intermediate rotational speed state. The duration of a turbocharger's lag depends on many factors among which its inertia, airflow efficiency, back pressure, etc. The problem is partly dealt with by fitting a turbo dump valve, which acts each time the driver lifts his foot from the throttle. The dump valve will evacuate the pressurized air coming out of the turbocharger while the inlet manifold is closed thus allowing the turbine not to stall and avoiding possible damage to its bearings. In race cars it is very common to fit oversized turbochargers in order to be able to produce enough boost pressure and assure a sufficient engine output. Big turbochargers display significant amounts of lag due to their increased rotational inertia. In such cases the dump valve is insufficient to allow the turbocharger not to loose too much speed when the driver lifts off. Additionally rally cars hold a turbo restrictor, which is regulated by the FIA. One of the restrictor' effects is to increase lag time. This is why in racing cars, and more specifically in rally cars, where torque and engine availability are critical factors, most applications use anti-lag systems.

 

During lag time the engine is much less responsive and its output well below nominal. To counter the effect of the turbocharger's lag time drivers used to anticipate the engine's reactions by accelerating well before they would have done in a non-turbo car. Others have used a technique, introduced by the German driver Walter Röhrl, known as "left foot braking" where the driver uses his left foot to brake the car while his right foot accelerates to keep the turbocharger in optimal load. Left foot braking is very hard on the brakes which are put into extreme stress but is very efficient in keeping the turbo spinning.

ALS was a simple idea but one that was relatively difficult to implement. Only when electronic engine management systems were advanced enough to allow taking into consideration many more parameters than in the past it became possible to use them efficiently in handling ALS. To the best of my knowledge Toyota Team Europe were the first to use it in racing (Toyota's implementation is known as Toyota Combustion Control System while Mitsubishi call the system Post Combustion Control System).

 

How ALS works

 

When the driver lifts his foot from the gas pedal the ignition timing is altered with sometimes 40° or more of delay (retard) and the intake air and fuel supply mixture is made richer. The inlet butterfly is kept slightly open or an air injector is used to maintain air supply to the engine. This results in air/fuel mixture that keeps getting in the combustion chambers when the driver no longer accelerates. The ignition being delayed, the air/fuel mixture reaches the exhaust tubes mostly unburned. When the spark plug fires, the exhaust valve is starting to open due to the ignition delay mentioned above. Additionally, the exhaust temperature being extremely high, the unburned fuel explodes at the contact of the exhaust tubes. Luckily the turbo sits right there and the explosion keeps it turning (otherwise it would slow down since its intake, the exhaust gases, is cut-off). The effect is vastly lower response times with some downsides:

 

A quick rise of the turbocharger's temperature (which jumps from ~800°C to the 1100°C+ region) whenever the system is activated

 

A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)

 

The turbo produces significant boost even at engine idle speeds

 

The explosions which occur in the exhaust tubes generate important flames which can, sometimes, be seen at the end of the exhaust tube

 

Reduced engine brake

 

The ALS effect is mostly dependent on the air allowed into the engine, the more air supplied the more the ALS effect will be noticeable. Consequently ALS systems can be more or less aggressive. A mild ALS will maintain a 0 to 0.3 bar pressure in the inlet manifold when activated whereas, when inactive, the pressure in the inlet manifold with the throttle closed would be in the region of -1 bar (absolute vacuum). Racing ALS versions can maintain a pressure of up to 1.5 bar in the inlet manifold with the throttle closed.

While the systems mounted in Toyota and Mitsubishi racing cars are relatively smooth and noiseless those fitted in Ford and Subaru cars are much more noisy and aggressive.

The bang-bang system owns its name to the loud explosion noises one hears whenever the driver lifts off. Most racing implementations have user selectable anti-lag settings depending on the terrain, usually three settings can be selected by the driver going from mild to very aggressive.

 

Note that some regional or national European events prohibit the use of ALS systems while more and more WRC events regulate the noise levels allowed by competition cars effectively disabling ALS.

 

Starting in 2002 new anti-lag techniques, such as Exhaust Gas Recirculation (EGR), are slowly overtaking the method described above as they are kinder on the engine's mechanical parts.

[Bdt]

Jepp absolutt,skal ha det på min.har vært i kontakt med noen på passionford forumet.vil ikke koste så mye(modder bare innsug og tomgangsregulatoren) men det er det å få modda org hjernen(P8) som er problemet.veit ikke om noen som gjør det i norge.og data sprut har jeg personlig ikke råd til og ikke vil jeg ha det heller.men veit du om noen Bige?

[Escorteren]

A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)

 

Det sier jo litt om hvor mange manifolder du må ha liggende, eventuelt hvor god du er til å sveise

Edited March 6, 2006 by Escorteren

[cosworth540]

må vel også ha en spesiell turbo for ALS.en vanlig turbo klarer ikke påkjenningen.

Blir også et vanvittig bensinforbruk med ALS

[Ovar]

Det finnes "light" versjon av Antilag , det spørs hvor mye trykk du skal ha...

 

Jeg venter på oppdatering av software på SECS Ecuen min , der skal det være mulig å legge inn Anti-lag....

Synd jeg må vente!!!!!

 

 

 

The reason for Anti-lag is, as it's name suggests, to decrease or eliminate the lag induced by a turbocharger. It is mainly used in rally where all Group A or WRC cars are turbocharged.

When you want big power out of a 2 litre engine you need a turbocharger, and the more power you want the bigger the turbocharger has to be. But a big turbocharger takes a long time to spin up and create boost pressure and that's where the ALS (Anti Lag System) comes in. Because every second a car is off boost a lot of time is lost on a rallystage.

 

To get rid of the lag the needs to keep spinning at full speed at all times. This includes when the throttle is closed for a gearchange, when braking for a turn and when you're a the start line ready to take off.

 

To keep the turbo spinning while the throttle is closed you need exhaust (lots of hot air basically) to keep turning the turbine wheel. This is how it works:

To get the ALS working you need this:

 

P8 ECU - Which the big-turbo Escort Cosworth already have as it was made for rally.

Pectel anti-lag babyboard - An additional module to the ECU.

Anti-lag valve - Replaces the original idle speed control valve.

Modified throttle body - The inlet and outlet ports to idle valve bored out.

Turbo with 360thrust bearing - So that it will last longer.

EGT gauge - So you know when your turbo and manifold is going to melt.

Wiring to "arm" the anti-lag and switch it off - This simply involves wiring in a switchable earth to one of the ECU pins.

This goes for so-called "mild" anti-lag (see further down for info), for the real WRC stuff you need another (very expensive) turbo, exhaust manifold and a few other bits.

 

With the ALS installed - when you let go of the throttle, the valve that replaces the standard idle valve in a modified throttle body opens to let the air continue through. The amount of air this valve can flow is the only thing that affects anti-lag, the less the airflow, the less effect the anti-lag has. Then the ECU retards the ignition timing by 30 degrees so the fuel is ignited when the exhaust valves are open and most of the fuel is already in the exhaust manifold and turbo. That makes lots of nice and hot exhaust to spin the turbo and create boost pressure.

 

A small "mild" ALS valve can flow enough air to make 0psi boost pressure at idle/off throttle (rather than -25psi of vacuum), sometimes up to 7psi of boost, which makes the turbo hit full boost almost straight away when you press the throttle. The big WRC anti-lag valve can flow enough air to produce 22psi at idle (or off throttle), which makes the car have no lag at all. That will increase the driveability of the car a lot.

 

Unfortunately the WRC ALS puts a big strain on the turbo and exhaust, whereas with the 'mild' anti-lag setup is practically as reliable as not using an ALS at all. It will gradually burn out your silencer baffles, but all that does is make your exhaust louder.

Some people say that the fuel will cause "borewash" making the need for a rebuild all the time. But that is not the case. The amount of fuel used in anti-lag is not enough to cause any significant bore wash (unless you use £5 budget oil), most performance cars fuel on overrun, unless they have been mapped for good emissions, not mapped like that because of reliability reasons.

 

Regarding the reliability of Cosworths with the mild ALS installed people have had it installed for up to three years without any problems at all even though it has been switched on at most times. The only real thing you have to be wary of with anti-lag is that Exhaust Gas Temperatures (EGT) go sky high but there's no real worry as you could be on the overrun for well over 30 seconds on 'mild' anti-lag before the EGT will get dangerously high. If EGT gets too high it could melt the exhaust and/or turbo. The engine internals will not have any problems.

 

For full-on WRC anti-lag the specs is as with 'mild' anti-lag but with a bigger WRC ALS valve, and a anti-lag turbo with Maram 247 shaft and turbine wheel with 7° cut-back blades, Nimonic wastegate spindle and everything nicely put together by a reputable company at around £1800 total. You will need that as the extra stop/start shocks and extra heat would eat a standard shaft in minutes. A stainless steel exhaust manifold may be handy too as it could stand more heat than standard one.

 

For road use you will not need more than 'mild' anti-lag, and for track use it might be best too as you're on track at sustained periods of time and the WRC anti-lag may be too severe for those long sessions.

 

The ALS system won't increase the outright power of your car but it will significantly increase the power delivery - much much more low down torque since the car gets on boost a lot earlier than without the ALS.

 

Back towww.wrc-cosworth.org

[Bdt]

aggresive als, P8 med als babyboard,modda innsug og tomgangs regg for ca 12000 kr

 

 

http://video.google.com/videoplay?docid=-6933030243990164610