Well we've been trying to tack down this jitter problem. Basically IPW bounces back and forth when it should be more steady. Today mrfred unraveled one piece of the puzzle:
Quote:
Originally Posted by mrfred
I've been putting some time into trying to figure out this issue, and there are a couple of areas where I can provide some clarification:
1) You guys may already know this, but the name "MAF filter" is somewhat of a misnomer. This value is used to calculate a weighted running average between the old master load value and the newly calculated master load (from the MAF). The formula goes like:
MasterLoad = [MAFfilter*MasterLoadOld + (256-MAFfilter)*MasterLoadNew]/256
2) SD master load is inserted in place of MAF master load further down in the master load calculation subroutine, so SD master load is not affected this weighting calculation, and thus any changes in the "MAF filter" value have no effect on the SD master load.
However, in looking a little further just now, I do see that there is a flag that gets set at the end of the subroutine where the weighting value is determined. The value of the flag is dependent on whether the weighting parameter is above or below 200. This flag doesn't affect the master load calculation, but it does affect some of the calculations for the fuel pulse width. This is the best candidate that I've seen for causing the jittery IPW issue. I'll see if I can look at it further this weekend and perhaps come up with a patch to test it.
EDIT: Having thought about it a little more, it should be pretty easy to test this. We can create a 1D table for the over/under value, and then set the over/under value to 255. Another over/under value to try would be 0. This value is below all the possible weighting parameter values. For the 9653 ROM, the address of the over/under value is 0x162C. Its a word length value, so use uint16 for the scaling.
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So, I'm gonna try:
<table name="MAF Pulsewidth reset (test)" category="Speed Density Tuning" address="162c" type="1D" scaling="uint16"/>
Unfortunately I'm gone till sunday night :P
More info on this subject here, we started a thread dedicated to it:
http://forums.evolutionm.net/ecuflas...ml#post7747496