But it's not as basic as it sounds. Let me try to explain - the throttle needs to be kept open at 20 degrees while the engine revs up to speed (3K RPM or so) and the program will inject fuel. it causes a sequential misfire when you back off and causes a LARGE flame to go shooting out the back when you take off. Probably not something you want to use on your Daily Driver on a regular basis.
Below is a write-up taken from the War Motorsports Tech files, written by Rob @ War Motorsports.
This is what happens to your engine at wide open throttle for sustained periods of time without the cooling effect of air rushing into the engine bay. It is caused by the phenomenal amount of heat energy created by the combustion process.
Engine power is created by one thing only, BMEP or Brake Mean Effective Pressure. This is the Dynamic (or actual) pressure created within a cylinder during the combustion process.BMEP is the "be all and end all" of the engine power game. Every thing we do to create power in any engine, is an attempt to raise BMEP in a controlled manner.
During the combustion process many things are happening but of interest to us here is the rise and fall of BMEP within a cycle of the engine. During an intake stroke air and fuel is drawn or pushed into the cylinder, the intake valve then closes and the upward travelling piston compresses this mixture. As the piston approaches Top Dead Centre (TDC) a spark ignites the mixture and the combustion process begins. On a scale of 1-10 the actual compression pressure of an engine is about a 1 or 2 when no spark is delivered for ignition. The pressure created by a burning and RAPIDLY EXPANDING air fuel mixture rates, about a 7-8. This pressure rapidly increases untill such time as 2 things happen. 1 The piston is forced down by its expansion (power is created) and the space created by the piston moving down creates a pressure drop within the cylinder. 2. The burning/expansion rate begins to slow down due to air/fuel depletion.
The point at which BMEP is at its highest is called "Peak BMEP". Its position within the firing cycle is studied by eDBD::ODBC::db prepare failed: (DBD: st_prepare/SQLAllocStmt err=-2) at incl_db.pm line 312. Can't call method "execute" without a package or object reference at incl_db.pm line 327. ngine designers and tuners all over the world. It is generally agreed that the point of peak BMEDBD::ODBC::db prepare failed: (DBD: st_prepare/SQLAllocStmt err=-2) at incl_db.pm line 312. Can't call method "execute" without a package or object reference at incl_db.pm line 327. P should fall within the 14-16 deg AFTER TDC. If we think of ignition spark, as the beginning of the combustion process, and we can establish that it takes 46-48 crankshaft degrees(usual average) to reach "Peak BMEP" then an assumption can be made that we should set ignition timing to start at 32degrees BEFORE TDC.(32+14=46) Have a think about this and understand it because it is important.
Now lets do something rather interesting, lets retard the ignition timing to something like 10 degrees after TDC. Suddenly we have a theoretical Peak BMEP at 56 degrees after TDC. Power has dropped significantly, in fact we have virtually no power-why?... Simple, the next step in our combustion process is the exhaust valve opening and venting of exhaust gases, and this is happening just after our retarded Peak BMEP. So effectively, our precious power producing charge is now burning and rapidly expanding inside the exhaust manifold. This is not much good for making power but it really make the turbo spin hard.
So if the turbine is spinning hard it must be making heaps of boost right? Yes, but we are not making any power because the Peak BMEP is all going out the exhaust valve.
So what good is it?
Easy. During a race we want instant boost, the moment we get on the throttle we want it there ready to go, just waiting for us. So how do we do it?
Anti-lag should only be operational during off throttle conditions otherwise power will be lost by retarded BMEP.
The first thing we do is keep the throttle open about 10% so that there is air available for the combustion process, then we retard the ignition timing by a huge amount which creates retarded BMEP, and large turbine driving pressures within the exhaust manifold. This in turn creates good strong boost even though the throttle is closed, but when you open the throttle and Ignition timing returns to normal the turbine is allready spinning hard and making boost so we have instant power.
Want more? ok.
Lets now say we want even more exhaust gas pressure to really get that turbine up to speed, because we are off the throttle and not trying to make power, why not introduce completely unburnt air fuel mixture into the exhaust for even more rapid expansion of turbine driving exhaust gases. The easiest way of doing this is to introduce an ignition based missfire which will dump a complete compression/firing cycle of air/fuel mixture into the manifold, where it is rapidly ignited by the next cylinders flame front. Now we have got some serious amounts of driving force going into that turbine and it is making huge amounts of boost in anticipation of the throttle opening.
This is how anti-lag works.
What I have described is a very simplified explanation of anti-lag and it can only be said that there are many many more variables which come into play. Actual degrees of retard and throttle opening are very different to the numbers I have described but I have used these as an ease of explanation.
