hah! i've been reading the manual.

can anyone elaborate on the PIM tables? i take it they are around for making easy broad changes with the commander.

but where as the injector correction maps use the arbitrary idea of 100% (being the factor for ideal 14.7 af), multiplied by the number you input to "correct" for the desired af... the PIM tables seem to all just use "100%". as opposed to some sort of correction number to be multiplied by 100%.

now, if there wasn't a boost table i would think "ok, this is all a universal 14.7 goal per 1000 rpm". but there is a load factor too that seems to be all 100%, no matter the load.

could someone explain this more completely, the manual doesn't spend much time at all here, and the best post i found in a search still wasn't quite there since it wasn't only about this function.

all these arbitrary numbers are killing me. why the hell didn't they just use injector duty cycles, rpm and atleast "kgm2" or whatever.

 

You are trying to make too much of nothing.

We know that the fuel correction map changes the base inj map by a percentage. It does this by fixed cell locations. What might be confusing is that it is displayed in two formats. When you view the whole table you might see 120 in a cell. When you go to update it, it shows 1.200. Either way it represents 120% or a multiplier of 1.2 against the inj cell.

The PIM Voltage and PIM RPM maps change the fuel for ranges of cells by PIM voltage(boost or vacuum) or RPM. It is also by percentage or multiplier.

As to the order that it is done; I do not think anyone knows excatly how it is done. But I would presume the fuel corretion against inj value would come first as it is always that value and might or might not be affect by the PIM corrections. You could be in a cell, and before you got out of it , PIM voltage might go to a value that says add more fuel. Such when you are in 5th gear at 2000 rpm and quickly floor the throttle. Vacumm to boost would change fast enough before you left that cell which is 400 rpms wide.

Either way it should not matter as to the order. If a correction cell is 120% and the PIM will change it and has a value of 105% and the INJ cell has 11.125MS, multiplying all three will get the same result no matter what order it is done in. Remember A * B = B * A from basic math.

Now if it was a combination of adding and multiplying, then it would make a difference. But only Mazda knows for sure. Anyway the difference would be too small to worry about.

 

ok, i'm a little confused on the math needed to make a theoretical global boost increase of fuel of .5 (re 14.57 table, my numbers were off in the last post obviously).

it should be more obvious on a cell by cell injector table basis since i'm dealing with calculated afr's, but that also means changing every single boost cell. i believe the PIM is there for this sort of thing.

the example the manual uses for calculating ARFs is "14.57/12.00(goal AFR)=1.214" the "1.214" is the percent, or multiplier over the "base" fuel map i take it.

i'm having trouble coming up with the math to add a theoretical (i know this would vary by engine air flow) .5 fuel ratio over the stock map over entire boost ranges.

hrm i'll try and post some futile attempts at calculations. since i'm trying as i post this. -goal = -.5 AFR, (adding fuel)
-14.57/.5= 29.14 - right that can't be going anywhere.

-14.57*.5%= .07285 - i thought this might but there is less than .07285 difference between for /12.00 and /11.5 . (14.57/12.00=1.214... vs 14.57/11.5=1.266... 1.266-1.214=.052) ok, but what does that .052 equal in changed percent...

gah, gotta give up, brain not working anymore.

oh one more thing, does the datalogit make any of this easier? mine is still on back order so i haven't gotten to play with the software yet.

 

For calculating new fuel requirements for any cell to achieve a given AFR, ends up being very simple. Easier if you have a DATALOGIC and do the re-calc function so that the fuel correction map has all 100s in it instead of values like 1.214 or 1.495.

Lets begin the process using an arbitrary fuel correction cell with 1.214 in it. “CF” will be total current fuel. “X” will be the value in the inj map which you can’t see without a DATALOGIT. “NF” will be new fuel requirement to change the AFR from 14.57 to 12. “AIR” is air used for combustion.

CF = (1.214)(X)
14.57 = AIR/CF = AIR/(1.214)(X),
AIR = (14.57)(1.214)(X)

You want to change your AFR from 14.57 to 12 for the above cell. Air flow is constant for that cell since it represents an area on the map determined by rpm and boost.

12 = AIR/NF, 12 = (14.57)(1.214)(X)/NF
12NF = (14.57)(1.214)(X)
NF = (14.57)(1.214)(X)/12
NF = 14.57/12 * (1.214)(X) = 14.57/12 * CF

Notice the new fuel requirement for changing from 14.57 to 12 is the ratio of the old AFR divided by the new AFR times the original fuel. Since A * B = B * A, just take the 14.47/12 ratio and multiple the fuel correction map value of 1.214 to get 1.487. If you enter a change in the PIM, it is still the same idea. The order of multiplying does not matter.

This is where problems arise with using only a commander. You cannot inter more than 1.495 in a cell.

 

thanks alot, i'm still not totally clear myself but i'm going to work the math a bit longer.

 

Try changing total fuel 1% for a 0.1 AFR change. It's close enough. Start by making small changes to your fuel and learn how the AFR reacts.