What needs to be changed when you change fuel pressure

[andysc3]

I'm losing fuel pressure on the top end. The base pressure is currently 58psi. I'm running about 9.5 psi of boost. Using an aeromotive boost ref fpr. If I set it to 50psi what tables do I need to change in the tune

[DrkPhx]

Have you determined the cause of the pressure loss?


If I set it to 50psi what tables do I need to change in the tune?
So you're just adjusting the boost referenced psi, correct? Usually the boost VE Table and/or MAF (if you're still running it) and possibly the injector flow rate. Is the fuel system vacuum or MAP referenced?

[O1Z06]

What injectors? I have ID1000s and they give you injector data for alot of different MAP pressures. I would have a look at their spreadsheet and see what changes per different MAP. My MAP referenced A1000 FPR is set to 46.5 psi, and with 15psi boost, inj duty is 81% without water/meth. If I remember correctly, I only changed B3701 and B4001.

But when did you notice the pressure drop off? All of a sudden or when adding boost the first time? Do you have a stock pump with a voltage booster?

[andysc3]

I'm running FIC 1000cc injectors, fuel pumps are a racetronix 255lph drop in pump and a Bosch 044 inline. Using custom fuel rails with a aeromotive fpr. The fuel goes from the stock feed to the back of the drivers Sid rail, crosses over to the passenger side in the front, exits the rear of the passenger side rail to the fpr then returns to the stock return line. Base pressure is set to 58psi. Once in boost it will go up to 62psi hold there till 6500 rpm then drop to 40 psi by 6800. And I am spraying 49% meth/water. Idc is at 60%. Running about 9.5psi boost

[joecar]

If base pressure is 58 psi (measured with reference open to BARO), then at 9.5 psi boost I would expect rail pressure to be 67.5 psi.

You will need to find the reason for the dropped pressure.

[joecar]

When you change rail pressure, B4001 should be relatively scaled by sqrt(P1/P2) and B3701 needs to be modified also;

since those injectors are large (will peg B4001) you would have already scaled VE/MAF... so now if you change the base pressure and rescale the IFR, you want to be careful, the VE/MAF do not need scaling in this case...

i.e. if you scale VE/MAF and IFR due to change of base pressure, then you have scaled twice.