what is a ve table?
a table that represents how much air flows at a certain rpm and manifold pressure. so at 50 KPA and 5000 rpm it flows x air so the ecm knows how much fuel it needs.
what are you doing when you tune VE?
you are analyzing fuel errors against the ve table (rpm and manifold pressure) and correcting the errors in the VE table.
there are lots of ways to do that.
what is a fuel error?
your ECM targets an AFR. in closed loop that is 1 LAMBDA (or you can call it 14.7:1 but that isn't really correct except for pure gasoline). in open loop or power enrichment it targets an AFR from another table. to determine the fuel error in closed loop you look at fuel trims. in open loop you look at your wideband.
so in brief, your ecm goes 'okay, this much air (because VE is this) and inject this much fuel' and you measure the result to see how far off it is and adjust that cell.
simple ve adjustment:
lets say you are at 1000 RPM and 40 KPA and in closed loop, your fuel trim is like +10% (your ECM is adding 10% fuel to reach its target) that means at the VE table cell closest to 1000 rpm and 40 kpa, you would *1.10 (add 10% to that value)
sounds easy but hard, right? you have tons of data. people do it by hand but it takes FOREVER.
to tune your VE table properly, you have to use analysis tools like spreadsheets or programs like my trimalyzer or tablehack, or commercial tools. some logging programs have a 'histogram' built in that could do it.
do you want to try tablehack? it's kind of medium difficulty but i can walk you through, basically you load logs, tell it what your VE table looks like, tell it how to figure out if you are open or closed loop whatever (filters) and it tells you what your correction averages are. you can even do more advanced stuff like pasting your VE table and do some corrections.
if you wanted to give me a CSV log and show me your VE table, i could make you a step-by-step, and then you could reproduce it yourself?
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