AIR FLOW HZ (range of 0 to 1600hz)

This is the actual signal the Karmann Vortex generator in the Mass Air Flow sensor (MAF or MAS) sends to the ECU. This tells the ECU the amount of air moving through the intake. Please note that this is not equal to air mass - the ECU also needs the barometric pressure and intake temperature (also located in the MAS) to determine the actual air mass entering the engine and the corresponding amount of fuel to deliver. Unfortunately, current limitations in the TMO Datalogger limit the reported result to 1606hz. However, the MAS is capable of sending out a signal up to ~2200hz or so to the ECU.

This is the actual signal the Mass Air Flow Sensor sends to the ECU. One important note here is the max the Datalogger will read is 1606hz. This is NOT the max signal the MAS can send to the ECU. The MAS is capable of sending out a signal up to ~2000hz or so. What you want to do is actually have the signal read 1606hz for most of the rpm range while at WOT. If you could extend the MAS hz signal line beyond the 1606 limit, you would see the graph line almost exactly mimic the fuel injector pulse signal line. That is because the ECU uses the MAS signal to tell how much fuel to add.

If you have some kind of piggyback fuel computer (VPC, AFC, PMS, MASC etc.) that gives a false signal to the ECU, you don't want to have the MAS hz signal set too low, say 1400hz at WOT. What this would do is tell the ECU that less air is entering the engine and the ECU would open the injectors a less amount of time for less fuel. You could increase your fuel adjustments on your AFC etc. but you don't have near the control the ECU does for the entire fuel curve under all the given conditions. What this means is, it's better to let the ECU control the fuel and deliver the most fuel it can from it's fuel tables and then if it's not enough add more by the way of your controller.

Example: Say your MAS signal is 1400hz. The ECU will run the injectors at say 75% on the fuel table in the ECU. You might have to add +25% on your AFC to reach the correct amount of fuel to get a good a/f ratio. It's better to have the MAS signal be 1606hz and then the ECU will run the injectors at say 100% on the fuel tables and your AFC setting would be 0 or nuetral. This would keep the entire fuel curve under the ECU's control. (these are just arbitrary #s for an example, not actual working parameters of the ECU)

Now VPC users are even worse off. The gain knob is just that, a total fuel curve gain knob. You are just broadening the entire range and not adding specific amounts of fuel at specific rpms. This is why you need a GCC or AFC also to control individual rpm ranges.

IMPORTANT! If you run the stock MAS you should watch for MAS overrun. This is when there is more air flowing through the MAS than it can "count" and the signal starts to break down. It's very easy to see with a logger. You will see the air flow hz go up to 1606hz and stay there (normal) but above some rpm range (5500, 6000, 6500, every MAS is different) the signal will start to fall below 1606 and become unstable or "jittery". If you look at the exact time the MAS starts to lose count of airflow, you will see the injector pulse signal do the same thing, become unstable. That is because the ECU is getting a corrupt signal from the MAS and it doesn't know how much fuel to give. It trys to mimic the MAS signal and the result is a corrupt injector open time signal. As you can imagine, that results in detonation starting and then timing retards to try and stop the knock. It's a vicious cycle, one thing leading to another.

What you would think to do to cure this problem might be add more fuel, that's not right though. All you need to do is get the MAS to not lose count of the air and then the MAS signal will smooth back out and so will the injector signal and the ECU will be able to give more fuel and the knock will go down and your timing will stay advanced. :-) How you do this is by BYPASSING air around the portion of the MAS that counts the air, cutting up the lower passage. Remember what we talked about earlier though about the fuel trims. If you bypass too much air it will run fine at WOT but the idle/part throttle will be too lean as the fuel trims will be maxed out at 140% and still not enough fuel. This is when you need an AFC to add even more fuel at idle/part throttle. Another way around this is converting to the 2G MAS setup but you will definitely need an AFC or equivalent then.