The way that anti lag works is that is creates enough exhaust energy to keep the turbo spooled while being off the throttle (no engine load)
The way in which is work is that the air/fuel mixture enters the cylinder as normal but rather than the spark going off when the mixture is compressed, it goes off when the air/fuel mixture is being forced out of the exhaust creating an explosion in the exhaust manifold, the energy from that then spins the turbine wheel of the turbo and keeps it spooled, it's also why rally cars cackle and pop a lot.
Other ways of reducing turbo lag, well twin turbos don't really reduce lag, but if used in a sequencial setup then they are quite effective at reducing lag, also you have a sequencial setup which utilises a big turbo and a small turbo, small one does lower rev band then gets phased out when the revs rise and the big one cuts in.
You also have what known as staged turbo charging or compound turbo charging.
What you have here is a big turbo and a small turbo but they work through the entire revband (or when they manage to spool up) the trick with this system is that the small turbo (the secondary) is the one that pumps out the most boost pressure and not a great deal of air and the bigger turbo (known as the primary) is the one that runs a lower boost but provides all of the air (you have to size it kind of like a big single, if your application requires 40 lbs/min of air then on a compound system the primary turbo must be able to flow that amount of air un like a twin system where it is half for each turbo) The reason for using a system like this are as follows:
1) The engine has a low volumetric efficiency,
Staged turbo charging is popular on diesel engines for this very reason, they generally have lower volumetric efficiencys than petrol engines due to them not having the revs to make the power (trade off here is that diesels make loads of torque...as you know...) So in order to flow 300 hp's worth air (for example) on a 2.0l diesel you would need more boost pressure than you would typically need on a 2.0l petrol, because diesels have smaller valves and ports and the cam lift isn't as high and the cam duration isn't as long, so the air/gas speed entering the engine is optimum for the diesel engines lower rpm range. So there for more restrictive in trying to flow more air.
Problem is that really only mega turbos (Garrett GT30 and upwards kind of size) can efficiently work in the dezired pressure you are going to need, so using staged/compund turbo charging would be the only option.
2) Reducing lag,
Although not it's primary function, compund charging can reduce lag in the same way that a sequencial system can (the one with the big and small turbos, not so much the twin ones....) Compound charging can be done by using a supercharger (usually a roots type) as the secondary which would make the usable torque band positively massive!
3) Something to brag to your mates about....
Come on.... how cool would it be to own a car with a turbo and a supercharger.....
I think I've covered the basics there, if you are still unsure then I suggest looking up claymore's project thread as he uses compound charging (supercharger and turbo) on his Volvo 850.
NOS can also reduce turbo lag by simply creating more exhaust gas energy which then can be used to spool the turbo sooner....
I've also seen a guy inject methanol and nos directly into his exhaust before the turbo to help spool it!, Apparantly it works rather well....
http://www.turbobuick.com/forums/al...ous-methanol-anti-lag-system-afterburner.html
There's the orignal thread I found while searching for ways to reduce lag on a turbo diesel, I suggest that you read it as it is very interresting....
Heres a video of it in action....
http://www.youtube.com/watch?v=WYsqF88qCvQ&feature=related
Also forgot to metion VNT or VGT (variable geometery turbos) reduce lag by altering vanes inside the turbo housing to speed up the exhaust gas to aid in spool up. It does this be altering the A/R of the turbo housing (small A/R for low down and high A/R for high up, and eliminating the use of a wastegate on diesel applications.)
