Hi, I just came acrosss a map called DZWOLA. After a first look it gives me the feeling that this map is ign retard when going outside lambda 1.0 in certain cases? In the case of optimum ZW this is active? Have you guys edited this map or do you leave it as it is?

This is how my 3.2 vr6 looks like (pic)

It's been ages since I read it but think it comes in handy for the fail safe mentioned in the patent, type of fuel etc. Can be done with timing changes na to fi, variable resonance mani etc

http://www.volkspage.net/technik/ssp/ssp/SSP_246.pdf

Flame in combustion chamber has different speed at different lambda values. This map represents this dependency. In those places where flame is slow (extra lean, extra rich) they advance ignition angle a little bit. And it affects actual ignition angle not only optimal.

This should be of concern if running for example E85.  Flamespeed drops as mixture get richer..  If Lambda = around 1.00 there is no ign correction. But my question how would DZWOLA look like if running E85. The picture below show that E85 reach 30cm/s around lambda: 0.85

Found this: Burn speed is greatly influenced by mixture density. If you have more fuel in the mixture, the fuel molecules are closer together and the flamefront will progress more quickly across the chamber.
 



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That curve made more sense to me aswell.. is it for pump gas?

The key points are that the best lambda efficiency is at around 0.86, and this point is called the Lambda for Best Torque (or Leanest Best Torque, LBT). This is an important point to note. ADDING MORE FUEL DOES NOT GIVE YOU MORE POWER. Lambda is simply a measure of the ratio of fuel and air in the cylinder. The only way to get more power from the engine (assuming you have optimised the ignition timing) is to burn more charge - the mixture of FUEL AND AIR.

The running limits of the engine are generally around lambda 1.2 on the lean side, and lambda 0.65 on the rich side. Outside of this region combustion becomes unstable, and eventually the engine starts to misfire as there is either too little or too much fuel for stable combustion.

Lastly, the catalyst window of operation is around 0.98 to 1.02, and the fuelling must be cycled between these two values in order for the catalyst to operate correctly. This will be important if you are fitting your engine management system to a vehicle that still has to comply with catalyst emissions limits for MOT or SVA. If you want to know why and how three-way catalysts work, have a look here;

Catalytic converter - Wikipedia, the free encyclopedia

Fuel Octane Number
We briefly touched on the RON value of fuel earlier, and I said I would explain a bit more, so here goes.

The octane rating of fuel is a measure of its knock resistance under fixed test conditions. For a description of knock, see the ignition section. The Octane Number scale is based around two known fuels. N-heptane, which was given an octane number of 0, and iso-octane, given an octane number of 100, for no other reason that these fuels were easily available in a pure form when this rating system was being developed. All other fuels are then tested using a single cylinder research engine of variable compression ratio, and compared against these two reference fuels. From these tests, the fuels octane number is derived. Note that these 2 fuels do not represent the ends of the scale – ironically n-octane has a RON of -20, and methane has RON of 120. Additives can increase this even further. US wartime aviation gasoline was commonly as high as 150 RON. Unfortunately many of these additives are either incompatible with catalysts, bad for the environment, expensive- or all three! This generally makes very high octane "race" fuel a rare and expensive breed.

There are several different ways of quoting the octane number. In Europe, we commonly use the Research Octane Number (RON). However, another (and some may say more representative method) is the Motor Octane Number (MON), which provides a value under different test conditions to RON, but still using the same reference fuels. In the US, the quoted value is sometimes the roaD Octane Number (DON), also called the Anti Knock Index (AKI), which is the average of the MON and RON values of the fuels. This used to be an important distinction, since fuels of the same RON may have different MON values depending on the blend of the main constituents. Nowadays however, with increasingly stringent legislation and requirements on fuel blends for cars, the RON can generally be considered as being 10 points greater than the MON of available pump fuel, and hence the DON and AKI is halfway in between.

Here is another important point to note. RUNNING ON A HIGHER OCTANE FUEL DOES NOT GIVE YOU MORE POWER. The extra power comes from advancing the ignition timing to take advantage of the better anti knock properties. Modern OEM systems do this for you (active knock control) and most high performance engines with cylinder individual knock control are now calibrated on 100RON fuel, and the knock control system adjusts the ignition timing to allow them to run safely on 98, 95 or even lower RON fuels. However, aftermarket systems (that I know of) still do not have this fine a level of control, and any "knock control" functionality is a safeguard at best. Therefore, as I said in the Ignition section, map the car on the fuel you intend to run. If you think you might want to run different types of fuel, then you will need to map the car on each type. As we will see, this is not just ignition mapping, but affects the target lambda maps too.

Volatility
As well as all the other requirements we put on fuel, it also has to cope with changing temperatures and barometric pressures. Remember I mentioned mixing the fuel with air? Well one part of this mixing is through evaporation, or vaporization. As we already know, gasoline is actually composed of a complex mix of fuels. Some of these will turn into vapours (gasses) at quite low temperatures. Others will remain liquid until they get quite warm. During starting the engine, the amount of airflow and hence fuel required is relatively small. This means that the physical mixing of fuel and air is less effective, since there is less charge motion to help break up the droplets of fuel and mix them with the incoming air. This is where we rely on the "light ends" of the fuel to vaporize. It is this part of the fuel that starts the car. Much of the rest of the fuel is wasted initially until the combustion chamber and inlet ports warm up, and we are able to increase the engine airflow. This is why we increase fuelling for cold temperatures, but we'll cover this in more detail in the starting section.

So when the weather is cold, we need a high volatility fuel that vaporizes easily to allow easy starting. The flip side of this is that when everything gets too hot, liquid fuel can turn to vapour in the fuel rail and cause a "vapour lock", whereby when you open the injector you get nowhere near the amount of fuel you expect (the density has decreased dramatically). This commonly occurs after the car has been driving until warm and then stopped for 20 - 40 minutes, allowing the heat of the engine to "soak" into the engine components and the fuel in the rail itself. To avoid this we need a low volatility fuel. We can also increase the starting fuel, just as we do when cold, to compensate for the reduced density effects.

To try and meet these 2 conflicting requirements fuel companies actually change the volatility of the fuel available during the year. In some countries this may be in 2 or 3 steps through the year. In the UK we normally just have winter (high volatility) and summer (low volatility) fuels.

As an aside, you've heard people say they left the car for a while and when they came back the petrol was "stale". All that means is that the light ends have vaporized from the fuel in the tank, and left only the low volatility fuel. In extreme cases this will make starting the car difficult, but in reality there is nothing much wrong with the fuel. Mixing it 50:50 with some fresh (preferably winter) fuel will normally solve the problem (if there is one) and mean you don't have to throw it away.

Fuel Density
Fuel does in fact change in density with temperature, significantly enough to warrant attention. The chart shows the curve that was generated for the fuel dispensing industry in order to correct the delivery of fuel pumps.



In the engine, our air fuel ratio requirement is based on mass. But injectors are flow devices. So in order to calculate the correct mass of fuel from the injector open time, we also need to know the fuel density. Or to put it another way, in order to inject the correct amount of fuel under all conditions, we need to correct the injector pulse width based on the fuel temperature, using the percentage corrections above.

Over-fuelling -- why do it?
You'll have seen tuned cars (usually turbocharged) at the track which when accelerating hard leave a trail of black smoke behind them. This is one side effect of serious over-fuelling. We can see from the theory above that we would ideally run around lambda 0.86 for peak lambda efficiency, but there are 2 good reasons for running richer than this.

Due to the high gas flow rate at high engine speeds, and under heavy loads, the exhaust components (e.g. exhaust manifold, turbo, O2 sensors) are subjected to very high temperatures. In order to keep these components at or below their temperature limits (800 to 950°C), the fuelling is increased (richened) to lower the exhaust temperatures. This happens because of the lower combustion temperature of mixtures richer than lambda 0.88, and the initial charge cooling effect of the additional fuel, as we have seen.

The very same cooling effects also reduce the chance of knock during combustion, since the in cylinder charge and combustion temperatures are lower. This is why some tuners take the approach of running extremely (some may say excessively) rich mixtures, in order to allow more spark advance, and to protect the engine components from excessive temperatures.

Personally that's not how I calibrate engines (who wants their car to look like a diesel when they tip in?), as I feel it's wasteful of fuel for a minimal benefit. It also increases the chances of other problems - more delivered fuel requires larger injectors, more pump capacity etc, and the excess fuel may increase bore washing effects (where the fuel literally washes the lubricating oil film from the cylinder walls), reducing piston ring and cylinder life. However, I can understand the rationale and the potential for a little more power, so if that's the only thing that matters to you, then feel free to try it.