My 1st use of TuneECU

[Power-Tripp]

The AFR table has little or nothing to do with the fueling outside of where the narrow band Lambda (O2) sensor operates. Above cruise throttle percentage (more than 6-8% TPS), changes to the AFR table do nothing to actually changing the mixture ratio.

For instance, at a constant 3500 rpm and 20% TPS load, changing the AFR table from 14.70 to 10.10 does nothing to the actual mixture ratio. Yet a 2% change in the fuel % trim table will cause a mixture change.

The fuel % trim table controls the F tables (TPS%). At low rpm and loads, where the L tables have priority, you need to adjust the L tables for mixture changes.

The F_L Switch table sets the change over point from MAP (L tables) to TPS% (F tables). This switch point can be rather abrupt. So abrupt in fact, that it can cause issues to smooth operation at the points where the change-over occurs. In the latest versions of TuneECU, the tables are set so that the numbers indicate roughly the TPS% point at which TPS takes over from MAP. In older versions, the numbers were a little bit harder to understand - a 24 actually was closer to 6% TPS.

L and F tables are used at all points. It is just that one has much higher priority under some conditions than under others.

For instance, at idle, if you change the fuel % trim table, it takes very large changes before you actually see a change in mixture. However, a small change in the L tables, will cause the same amount of change to the mixture ratio.

And at a constant 3500 rpm and 20% TPS, a 3% change to the L tables has almost no effect on the mixture ratio, but as soon as you roll on the throttle, the acceleration compensation will increase by about 3%.

If you use a wideband Lambda/AFR meter, watch for changes in ignition advance and cylinder heat that will play havoc with getting consistent results. Both of these alter the residual O2 in the exhaust gases, and this alters the reading from the wide band Lambda meter even when no changes to fueling have actually occurred.

I hope this helps.

 

[dougl]

Tripp, just for my understanding, the numbers in the fuel tables are volumes of air. If not with the A/F numbers, how are the numbers in the fuel tables related to the fuel pulse?

 

[Power-Tripp]

A larger number increases the injector pulse unit (IJPU), and smaller one decreases it. Don't let the units of measure fool you. This is the same with the MAP tables as with the TPS ones. But they do acti differently due to the main sensor input.

Realize that the software we use is an interface that alters the ECU parameters for us, so that we do not have to modify the ECU code directly as we used to do with removable ePROMs in the past.

It doesn't matter if the interface fueling table is set up in units of air flow, units of fuel flow (IJPU), volumetric efficiency % (laughable), Brake specific fuel consumption, inches of mercury, inches of water, hectopascals, kilopascals, or Martian military units. If we increase the units 2%, the ECU opens the injector longer - working backwards from a fixed close timing.

Now, just because we alter the opening time 2% does not always mean that the injector(s) flow 2% more. There are issues with opening delay and rise time that throw a wrench into exact calculations - especially as opening times become smaller. THEN there is the issue of units used and the actual operation of the interface, injector, fuel system, etc. For instance, with a Power Commander, the actual flow decreases by a large amount with a single digit change in the cell(s) as you move away from zero (both positive and negative). TuneECU and TuneEdit do the same, but not with as great of a variance.

As a result, we just have to give the engine what it wants, and don't get all wrapped up in the units used.

 

[dougl]

Have you been able to eliminate decel popping with changes to the L tables? I have improved it but never eliminated it. What do you think about getting rid of the L tables altogether by adjusting with the L-F switch? Then trimming the low TP in the F tables?