jjcuff1

I posted earlier but too winded.

So for a 19# southbays in a 305. if you know from the injector charts and FP readings your injectors will X. In the case of the southbays. the chart for hi slope is 0.00544 lb/sec so x 3600 = 19.6lb/hr @ 39psi

so say I am flowing 17.6lbs after adjusted. do i just input the expected actual value or do I correlate the real value to some ratio of the stock 19lb figure?

RBob

iTrader: (1)

What you are asking is not easy to answer. I've been hacking a calculation out of the F*rd injector data sheets for some time. And I still don't have it right. Close, real close, but not dead on.

Still working on it.

As for the data, need to fit the compensations versus fuel pressure curves to the set data (slopes, brk-point, and min pw).

RBob.

jjcuff1

Yes I understand you can get into the details trying to figure out the theoretical fuel needed by BFSC. But trying to get 1 formula to fit the injector is not the way I read the charts, They are all look up charts that effect the a few set points. I see this as 1 chart
of Y = Fuel (lbs) and X = PW (ms) then the 2 slopes low and hi with 1 set point for the cutover from lo to hi is the fuel _bkpt. The lookup tables for PSI adjust the slope and cutover points. The Battery voltage with PSI adjustment is its own look up you plug into the Bin

In my case I think I am at 38psi. Not 44 but the south bay run at 39psi so not too bad for short term trials. I am then about 94% of the flow rate. Using the 2 slopes and psi adjustment my low slope is 19.8 and the hi slope is 18.4. and my cut over is about 2ms of PW.

I idle at 1.9PW-2.1PW so I am 99% of the time always in hi slope. I didnt zero my low PW table and my battery table was off like 30%! all my values were 30% higher then listed. (maybe why I had to add so much fuel to the MAF?)

So I was running a 16.8contant and 30% higher battery volt values. I am redoing to the 18.4 value and new battery table and 0 low pw. Maybe that will help the rich idle but lean top. Makes sense

Also the slope cut over is so small, the I think has little impact to worry about other then idle tuning. in see the table

RBob

iTrader: (1)

If I understand what you are asking, use the high slope fuel flow for the injector flow constant in the BIN. Which in your graph is 18.4 #/hr.

RBob.

jjcuff1

Yes I think I will try that 18.4. I am at 16.7 and it seems like the spot. since at higher values it seems to run lean at top idle gets richer. It does seem to run better at higher values but rich/lean issues but I never tweaked the battery table before when I upped the inj constant. I had that backwards too. Lower PSI I guess flows more at higher PW therefore needs less PW added in the Battery tables.

jjcuff1

I was confused from post here where for example people with 24# fords meant to run at 38psi now at 44psi will flow higher. So they backed the 22lb bin constant to say 19. to offset the flowrate.

I was not sure if the bin code uses a fixed vale of 22# where you need to have as close to that value as possible hence the conversion or if it is just a formula. Plug in the inj constant and it will calculate PW needed based on MAF/lv8.

That said for the ford injectors above, if you have the data sheet, you should just see that at 44PSI I will flow 26# and you can enter that value to match the actual flowrate. I think the problem people run into with that is that for say a stock setup they do not need 26lb of fuel! So they scale back the inj constant to lower the PW calculated without messing with the any other MAF/VE tables

jjcuff1

Well I am truly excited. Talking thru this thread I went back and double checked my tune. Reset the IAC/IDLE and checked FP. I was running 36-37lbs with vacuum at idle. I idle rock solid at 21". AT KOEO I go to 42lbs and sit at 38lbs for minutes.

My previous tunes I kept going down in my injector constants. Adding more fuel. I was still running lean at 16.7-17.4 constants. I really didn't mess with Battery vs PW table. I found if I added more PW in the table I was super rich at idle. so I left it alone after some tweaking down.

So no vac attached at idle my FP is 42psi. Using the charts from southbay and checking the multipliers for the high slope table and battery table I found that:
I needed to bump southbay battery table up by 2.5%. (this meant like 20% higher then my APYM bin)
and the hi slope was 3% HIGHER then the southbay slope.

Doing a spreadsheet to get the values for the bin I arrived at a constant of 20.1 and some big changes to the battery table. I also zero out the 1.9+ pw to compensate for the low slope which is calculated at 22lbs up to 2.5pw.

Long story short.... I kept my previous tune and changed the inj contant and battery and low pw table as stated above and wham, idle smooth and RICH even at AE/PE running 127-129 BLM across all MAF tables with just short run and way more torque!!!

I am still seeing some knock but now it is just at high lv8 under PE. I made a lot of changes in other bins. My O2 swings looked good and flat at PE around 990mv.

Not sure if too rich or now at 8 degrees I have too much timing and too much fuel.. Either way it is game changer to settings