Setting injector control tables for return style fuel system with vacuum fpr 99 ls1 f

[1hotroc]

Hello all. Im upgrading to a return style fuel system in my 99 SS . I like the idea of having engine vacuum control fuel delivery needs with the adjustable fuel psi regulator rather than the not so accurate injector data in the tune. Anyway, what parameters do I need to change in hp tuners injector control settings ? I already flatlined my injector flow rate vs kpa to 42.1 across the board 0-80 according to the FIC injector data card. Is there anything else ? Want to make sure I do this correctly. Thank you

[blindsquirrel]

Offset vs Volts vs VAC has the same 0-80 KPA axis, that needs to use only the 0 KPA column, pasted all the way across, too.

Just curious, why is returnless data inaccurate? All it does is use a fixed 58 PSI as one half of the calculation, and MAP KPA as the other. If the fuel pressure is variable for whatever reason, or MAP is something other than what the sensor reads, you'll have bigger fish to fry than any (assumed) lack of precision in the bench-derived datasheets.

[Alvin]

The fixed 58 psi is much more accurate.

The vacuum referenced regulators are almost never truly 1:1

[1hotroc]

Hey Blind squirrel you are correct I do have an underlying problem! In my case I think Im getting erratic fuel psi because of heat radiating off my kooks long tubes with cats on my fuel lines? I believe its messing up my fuel psi causing my fuel trims too go crazy erratic with fic data in my tune. However now I switched to the settings with return fuel system and my trims are much better. I still need to try and figure out why my fuel psi is erratic especially after car warms up fully and on a wot pull the pressure drops dangerously low that I can’t continue the run. This was same problem I had with old fuel pump and stock returnless system in place . Going to put some DEI heat wrap on the lines and see what happens . Right now the fuel lines are reaching temps up to 180 degrees measured by cat converter ����

[1hotroc]

Ok. Thought I would ask another question on this topic regarding a return style fuel system using fuel psi regulator. So if I keep my fuel psi constant at 58 psi like factory . No vacuum line hooked to fuel psi regulator can’t I just leave my injector data alone all together ? This has me so confused . I’m having erratic fuel trim issues when I activate closed loop STFT. O2s are indicting mad rich after I dialed in my afr with my wideband. Maybe I’m missing something but I want to make sure I have injector data set correctly whether I use vacuum port or not on the fuel psi regulator. If I set fuel psi to 58 with vac line disconnected then attach vac line it drops to like 50-53 psi and I don’t know if that’s right to tune off either ? I think these are meant to run 58 psi constantly ? Sorry so messed up trying to get things right. Thank you in advance for reply’s

[Ratssled]

You may have more than one problem.
Yes, vacuum will pull the regulator down.
Gasoline boils at around 100 degrees.
IAC and RAF may not be right.
You may have a few small exhaust leaks. A shop vac will help you find them.
What do the plugs tell you?
Try to define the problem the best you can, and don't focus on symptoms alone. What else could it be, but is not?
The solution is often easier than what you had originally thought!

[blindsquirrel]

It's not a 'return style fuel system', as far as the injector data goes, if the reference hose is removed. 'Return style' is shorthand for 'referenced to manifold'. If it's not referenced to manifold because the hose is removed, then it's the other one, 'referenced to atmosphere', which is commonly shortened to 'returnless'.

[1hotroc]

Ok thank you both for the feedback. Iac and RAF will be revisited but The fuel trims off are also apparent on part throttle conditions So that would take RAF and iac out of the equation I’d think. My real question is now with vacuum port connected referenced system . Can I tune it that way at the lower fuel
Psi 52-53 psi? Or would you set fuel psi to 58 psi with vacuum hose connected already? That’s directed to blind squirrel thanks. Once I know the avenue to take I will then be retuning my VE in open loop and activating closed loop to see if I still have trims way off or not . I’m pretty much starting from
Scratch . Want to make sure I go about it correctly 100 percent that’s why I ask the question. Thank you

[Ratssled]

I'm sure that you'll make progress once you sort out the fuel system, which means understanding how each type works. Unfortunately your line of questioning comes across as someone who is looking for more of an echo than an answer, and I suspect that doesn't work around here.

[blindsquirrel]

The injector data can be set up for whatever the fuel system type & pressure is... but you'd need to make a decision on what it's going to be and what you need it to do first.

If you only have the 'returnless' data (like what you get in most all aftermarket injector datasheets) and need to convert it to referenced style, you copy the '0kPa VAC' column and paste that into every column. That's for both Flow Rate and Offset vs Volts vs VAC. If it's non-referenced/returnless then you use the full tables as supplied in the sheet.

If you need it for a different fuel pressure, easiest thing to do is use data from the E38 tables, but that will require some interpolation to fill in the places where the different formats don't line up. You would use whatever column's kPa Delta most closely matches your new fuel pressure (300kPa = 43psi, etc.).