I've been agonizing on how to alter the "Injector Offset" parameter table in TunerPro (using EEx 4.1 xdf). I revisited the work above and started doing pen and paper exercises with the Ford datasheet. Staring at a pdf really doesn't help me work the numbers into my brain in a useful way. The top left table of the Ford Datasheet is a set of constants, to be multiplied by the appropriate multiplier in respective tables.
ALOSL (lbs/sec) multiples against its corresponding multiplier for each given pressure in the FNPW_LSCOMP table
AHISL (lbs/sec) multiples against its corresponding multiplier for each given pressure in the FNPW_HSCOMP table
FUEL_BKPT (lbs/) multiples against its corresponding multiplier for each given pressure in the FNPW_BKCOMP table
MINPW (ms) of .776 is the minimum consistent pulsewidth these injectors deliver at Ford factory pressure of 39.15psi
FNPW_OFFSET multiplies its whole table by its corresponding multiplier for each given pressure in the FNPW_OFFCOMP table
Now, since we lack a multiplier for 43.5psi in each multiplier table, we need to find that, or get as close as we can so we can use a reasonable value for each table. Again, I used Excel to graph this and stretch the x axis to get the values as close to correct as I could manage.
1) For minimum pulsewidth, I fudged by just calculating the proportion of 39.15 to .776 and got 43.5 to .851. I also tried using the Bernoulli equation, which we normally use to alter the flow vs pressure change, to find a relative minimum pulsewidth at 43.5psi. That method returned .776ms at 39.15 vs .8179ms at 43.5. Converted to usec, those are 776 and 817.9usec. Math geeks, please correct me on which of these 2 methods, or neither!! This may be off!! Time or pressure, or a blended value of both, not sure which is better... or even accurate.
So in TunerPro the STOCK "Injector Offset" table shows:
(Again, this is the stock table)
BPW | Adder
usec | usec
488 | 381.5
549 | 351.0
610 | 305.2
671 | 274.7
732 | 244.1
793 | 213.6
854 | 198.4
915 | 167.8
976 | 152.6
1037 | 137.3
1098 | 122.1
1159 | 106.8
1220 | 106.8
1281 | 91.6
1342 | 76.3
1403 | 76.3
1464 | 61
1525 | 61
1586 | 61
1647 | 45.8
1708 | 45.8
1769 | 45.8
1830 | 45.8
1891 | 30.5
1952 | 30.5
Continuing on from here, I'm going to use .818ms as the Minimum Pulsewidth. With the calculated offset at 14V, That minimum pulsewidth would take a total of 1.6863ms for these injectors at 43.5psi. Low pulsewidth adder falls at and below a point where flow becomes linear, somewhere between 122 and 124usec. The table shows a parameter data point of 854usec. **This pulsewidth intersects with 14.0V and 14.4V offsets in the Injector Voltage Offset table.** So, I think BPW below 854usec is where the low pulsewidth adder is particularly important for this injector. Some have had to experiment with different injectors to see what they do vs. what the engine wants with each specific injector/ manufacturer to find where to increase and where to decrease values. Some have zeroed out the table completely and dialed it in by feel/ AFR at low RPM/ part throttle. I guess the point is that at/ below the 793-854usec BPW is where most of the "adding" would be, at the "knee" of the low slope and somewhat less so above, ending in a zero value at or somewhere before 1952usec (max BPW in the low pulsewidth adder table). I'm thinking this can give a much closer place to start with dialing this in.
2) My 'close enough' value for Low Slope multiplier at 43.5psi is 1.076. Multiply this by the Low Slope Constant and you get .010784748 lbs/sec in the low slope. Multiply this by the length of the pulsewidth in sec/msec/usec at any given RPM vs MAP vs Hz/ g\sec and you get the delivered fuel mass for that pulse in the low slope, if the resulting mass is < .00001336 lbs.
3) My 'close enough' value for High Slope multiplier at 43.5psi is 1.0584. Multiply this by the High Slope Constant and you get .009041 lbs/sec in the high slope. Multiply this by the length of the pulsewidth in sec/msec/usec at any given RPM vs MAP vs Hz/ g\sec and you get the delivered fuel mass for that pulse in the high slope, if the resulting mass is > .00001336 lbs.
4) My 'close enough' value for Fuel Mass Breakpoint multiplier at 43.5psi is 1.0091. Multiply this by the Breakpoint Constant and you get a breakpoint fuel mass of .000013360484 lbs. as the switch point from low slope to high slope.
5) These are my slightly tweaked Injector Voltage Offset values with these injectors at 43.5psi:
Volts usec
0 | 213
1.6 | 213
3.2 | 6011
4.8 | 6011
5.2 | 5004
5.6 | 4211
6 | 3540
6.4 | 3112
6.8 | 2777
7.2 | 2532
7.6 | 2319
8 | 2166
8.4 | 2014
8.8 | 1861
9.2 | 1739
9.6 | 1617
10 | 1525
10.4 | 1434
10.8 | 1342
11.2 | 1281
11.6 | 1190
12 | 1129
12.4 | 1068
12.8 | 1007
13.2 | 976
13.6 | 915
14 | 854
14.4 | 823
14.8 | 793
16.4 | 396
18 | 122
19.6 | 0
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