this is the write up i done for fast ford mag a few months ago

What is Anti-Lag?
There is a lot of talk about what it is, and how it works, and usually what you hear is a load of old cobblers. Were gonna try and give you an insight and tell you what it actually is.
The reason for using an Anti-Lag System (ALS for short) is, as the name suggests, to reduce or eliminate lag produced with a turbocharger. You can run ALS on any petrol turbocharged car, you just need the correct parts and management to be fitted.
To get rid of the lag, the turbo needs to be spinning at high speed at all times. This includes when the throttle is closed for gear changes, or when braking for a turn, or simply at the start line ready to launch.
To keep the turbo spinning while the throttle is closed you need to create enough exhaust gas to keep the turbine wheel spinning in the turbo, ideally as much as if you were on throttle.

How does it work?
When a car has Anti-Lag fitted and switched on, when you let go of the throttle, a valve will open and continue to let air flow into the engine, bypassing the closed throttle.
At the same time the ECU adjusts the fuelling and retards the ignition to about 30 degrees so fuel is ignited when the exhaust valves are open and most of the fuel is already in the exhaust manifold and turbo.
This process will normally slow down the car when off throttle, but the boost pressure, rather than going to 15/20 psi of vacuum will stay at a positive boost level (even at maximum boost if the setup is effective enough) at all times. Therefore the moment you step back on the throttle the car will take off like a rocket with no pause for the lag at all.
Another big advantage of ALS is that it greatly improves part-throttle power. It makes it feel like your driving a big capacity V8, not a small capacity turbo car and gives excellent throttle response when you are driving on and off the throttle and will make the car quicker.
And of course, you get the mental rapid-fire bangs and flashes of flame from the exhaust associated with ALS too!
The main thing that will change the characteristics of ALS is the amount of air the throttle bypass can flow. Most road cars will use a modified version of their standard idle control valve, but they aren’t nearly good enough, they can only produce a mild Anti-Lag effect but it still makes lots of noise.
The only real drawbacks with ALS is that its hard work on the turbo, the heat created is immense, often over 1000 degrees C which most turbos can’t handle for long periods as the explosions of fuel in the exhaust manifold and the turbine exhaust housing can often damage weaker turbos and manifolds.
Although, there are some cars out there that can take ALS with ease on the standard turbo and manifold (the rumor that ALS destroys turbos and manifolds in no time is rubbish) but on others I can cause big problems.
Your best bet is to find someone who has fitted ALS on a similar setup and work from their experiences, as it varies greatly from car to car.
Anti-Lag is not cheap tho, mainly due to the fact you need a suitable engine management system to run it, along with a wiring loom and the car will need to be mapped to suit too. Then there is the cost of buying the appropriate throttle bypass valve which depends on the car and the setup.
Autronic management is commonly used, your best off contacting Mark Shead at M.A.D. on 07768 356204 for that, or you can use your Pectal P8 with an add on to run ALS.

What alternatives are there to ALS?
Another simple, but very effective Anti-Lag system can be to run nitrous. You could run a setup where jets of 50 to 70bhp are used at the moment you floor the throttle, and it can be set to switch off when the boost pressure reaches 15psi for example.
Nitrous creates a lot of exhaust gas so the boost level arrives very quickly and you will find that you don’t actually use that much of it either, but you will also benefit from the extra power nitrous makes too.
Obviously using this method is not ideal, and you will not have the part throttle advantages of full blown ALS, but it is a good, and dare I say cheaper alternative to ALS.
One setup people often confuse as Anti-Lag is simply launch control. This is when a car is held at a set rev limit before the clutch is dumped and the car takes off. You still get the popping and banging with the odd flame spit from the exhaust, but it’s a much simpler setup. So if its not ALS, what is it?
With the flick of a switch, the driver can lower the rev limit to whatever he requires, usually 5000rpm but its easily adjusted, so he can sit on the start line with his right foot firmly pressed to the floor and the revs will not go any higher than the pre set limit.
The advantage of this setup on turbo cars is the un-burnt fuel ignites in the exhaust manifold, much like ALS and spins the turbo up creating boost while stationary.
It’s a good setup for drag racers that won’t get any benefits from using ALS.

So what do I need to fit ALS to my car?
1. P8 ECU (the other Webber ECUs cannot retard the ignition beyond the required point) and Pectel board with MTC (Mountune Torque Control) board, or other aftermarket management systems capable of running ALS.
2. Modified idle speed control valve.
3. Modified throttle body (to allow more airflow through the butterfly bypass).
4. Ideally, a Maram shafted turbo to withstand the extream heat that ALS produces.