hehe, i started pluggin numbers in corbins formulas, but im lazy and thought someone might have already had experience here
I just ordered 30# injectors (approx 315cc), and i wanna replace the hahn fpr with a vortech unit. still deciding b/t the standard and the super. i like the super, but the standards are 1/2 the price
I have the hahn stage 1, adding my own spearco fmic. other than mbc and bov, its the hahn kit tho.
wondering what ratio is gonna be my best bet w/ the 30lb injectors, stock fuel pump, and the hahn inline pump.
if anyone has any feedback, great! otherwise, back to figuring out all the formulas, hehe
#11858, "RE: What ratio FMU disc...." In response to Reply # 0
ok, need a lil help to figure out where to go from here...
k, using corbins page, and rc engineerings page...i know that to get my desired hp level (240 at the crank), and keeping a safe 90 psi fuel pressure, the 30lb injectors i got are PERFECT, using a 85% duty cycle, and .60 BSFC for turbo cars.
what i dont know how to do is figure out what my idle pressure should be.
im assuming once i know that, then figurintg out which fmu ratio disc is easy (just figure how much more fuel i need to get me to 90 psi, and use the boost level to figure that)
so question is, how do i figure out what my idle pressure should be?
#11859, "RE: What ratio FMU disc...." In response to Reply # 1
Seriously...its all on those pages I made. From idle pressure to full boost...all the basics are there. I even made a full example problem. If you find that you need to run a really low idle fuel pressure, then you should probably invest in a S-AFC. Also, I mentioned this on one of the pages, but I think it bears repeating. If you made the calculations with a duty cycle that is lower than 100%, then you will need a S-AFC to fool the ECU into lowering that DC. If you don't use a S-AFC, then the ECU will still run the injectors at near 100% and you will have alot more fuel than you expected. I'll edit the pages to make this more clear, because I know people won't read every line of every page.
#11860, "RE: What ratio FMU disc...." In response to Reply # 2
So the ecu will run the injectors at 100% DC w/o a SAFC... does the ecu run the stock injectors at 100% DC all the time as well? i didnt know that, still trying to figure all this out, thanks for all ur help.
if the ecu is going to run the injectors at 100% DC all the time, i should actually run lower fuel pressure (60-65 psi instead of 90 according to the formulas)
figuring out what idle pressure is on the "which pump/fpr?" page right? I need to know what the current fuel pressure is to figure that out, correct? and i think i read that stuff is in the HRC manual (47-50psi idle, and 110-120 psi at full boost for a stage 2)
#11861, "RE: What ratio FMU disc...." In response to Reply # 3
>So the ecu will run the injectors at 100% DC w/o a SAFC... >does the ecu run the stock injectors at 100% DC all the time >as well? i didnt know that, still trying to figure all this >out, thanks for all ur help.
At WOT, the ECU will run the injectors near 100% DC. I don't know how "near" that number is.
> >if the ecu is going to run the injectors at 100% DC all the >time, i should actually run lower fuel pressure (60-65 psi >instead of 90 according to the formulas)
If you don't plan on using an S-AFC to lower DC, then you should plug a higher DC into the formulas (.9-.95?). You have to match your formula inputs to what you actually plan on doing. I really would suggest using a S-AFC to fine tuning.
>figuring out what idle pressure is on the "which pump/fpr?" >page right? I need to know what the current fuel pressure is >to figure that out, correct? and i think i read that stuff >is in the HRC manual (47-50psi idle, and 110-120 psi at full >boost for a stage 2)
47-55 psi under idle vacuum 80-90 psi at 6 boost 105-110 psi at 9 boost
If you still have your car in stock stage II trim, you can unplug the FPR vacuum line and see what pressure you get at 0 boost. Should be 8-12 psi above your full vacuum pressure.
The Example problem is solved for an HRC II kit going to larger injectors. Use it as a guide; alot of your numbers should be close.
#11862, "RE: What ratio FMU disc...." In response to Reply # 4
Hey Corbin, thank you soo much for your help on the fuel system set up. Your pages clear up alot of questions that I had.
Ryan...if you need a vortech 12:1, I got a complete new (never used) for sale if you want it. I will let go for 90$ (new is 150 if I remember correctly) only because I took off the AN fitting and was going to install 1/8 NPT barbs but never got around to it. Let me know what you think.
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