I have a question,..if you change just the VE table, or just the AFR table for that matter...How does the other one change to match when driving?
Always been a grey area fo me. It makes sense to me that you'd just set target AFRs in the map, and the VE table gets there via EGO correction...I know that that process is capped at 10%+/- ( I think)
AFR's make sense, VE tables are just a bunch of numbers. If you tell the ECU that you want it to be 12:1 in an area, but the current map is at 11.3:1 and its corresponding VE table "VE analyzed" to match, whatdya do to just jump a whole AFR point towards leanie town w/o guessing at the VE table?
To simplify the equation.
PW= REQ FUEL* (MAP/100)* (VE/100)* (E [all enrichments])* AFR adjustment [stoic14.7/AFR table]+ DEAD TIME
When you are tuning the AFR table is already set, to change the fuel value we adjust the ve table at that rpm/map point. this in turn affects the pw output.
in this example we are tuning a cruise range at whatever rpm doesn't matter just the map and ve number of the cell matters.
pw=req fuel* 45kpa/100* 100ve/100* (all enrichments including ego)* AFR adjustment [we want stoic for this example] +dead time
req fuel=10 45/100=.45 100/100=1 e=e[no enrichment in this example] AFR= 14.7/14.7=1* DT=1
pw=10* .45* 1* E[lets call this 1]* 1 *1
pw=4.5
lets say this pw results in a lower afr than we want. basic math will get us there. luckily the actual pw is not what we are tuning with we change the actual ve number so the correction is simpler.
we have a afr of 13 but we want 14.7 we just divide what we have by what we want then multiply the ve number by that amount.
have13 want 14.7
13/14.7=.884 now we multiply our ve number above by this amount
ve=100*.884 ve=88.4 this is our new ve number in that cell and will result in a afr of 14.7 instead of 13
now lets see how much that changed out pw
pw= RF10* 45kpa/100* ve88.4/100* E* 14.7/14.7* DT=1
pw=10* .45* .884* E* 1* 1
pw= 3.978 you can see our pw dropped almost.6ms less open time resulting in a lower AFR
now that we have tuned this cell to 14.7AFR we want to lean it out further for gas mileage.... since we already have the ve table tuned so the AFR matchs the AFR table changing the VE table is not the way to go. Lets change the AFR table instead.
pw= RF10* 45kpa/100* ve88.4/100* E* Stoic AFR14.7/ [NEW AFR TABLE VALUE]15.2* DT=1
pw=10* .45* .884* E* .967AFR Table change* 1
pw=3.858 you can see that the AFR table change from 14.7 to 15.2 has reduced fuel by 3.3%
All values in the AFR table are based off of the stoic value of 14.7 when incorporate AFR has been selected in the general settings menu for those of you whom I have helped this is always turned on when I adjust your tune.
In the equation this value acts as a multiplier, you can have 2 VE table cells with the same value but different AFR targets resulting in different output fuel values.
The takeaway here is that if you tune the VE table to a safe AFR value that matches the AFR table you built then when you get to the dyno you only need to adjust the AFR table in that area to get a correct no guesswork AFR output. this is how I did mine I set my AFR table to 11.5 and tuned the VE table to achieve 11.5 on the street then at the dyno I changed the AFR table from 11.5 to 12 and got a dead on 12AFR on the dyno.