Fuel Pressure for Vehicle Swaps

[GHuggins]

Found it.

There are 7 switches in total. Default, hot, crank, high flow, cold, low flow, normal. They are defaulted to off. When switched on, the ecm will use the respective fuel pressures in [ECM] 7030 through 7035

So once done and assuming the vehicle is actually equipped with a fp sensor, it would basically adjust fueling like it had a fpcm even though you're running a vacuum ref regulator?

[hjtrbo]

There is no fuel pressure sensor required. You tell the ecm what the pressure will be. The way the values are input makes me think the fuel reg would not be manifold referenced. If it was to be manifold referenced, then the only 2 scalars are the low and high flow, I can't see that working out very well???

[blindsquirrel]

I think those would just be the numbers it uses for calculating the pressure delta.

[hjtrbo]

Yes, that's what I mean right, it wouldn't work out well on a manifold referenced referenced system. You'd have to convert the fpr to a fixed reference setup.

[blindsquirrel]

Just flatline the IFR & Offset tables like you do any other time FPR is manifold referenced.

edit: In other words, the Delta is always the same as whatever the reg's base pressure is.

[07GTS]

only thing that may help is if u have staged fuel pumps and the second pump bumps up the base pressure a little and throws it out a few psi, if it was able to see the pressure it could adjust the delta to compensate

[hjtrbo]

Now that's a good idea. Mine knocks it up about 2 psi then falls away a little as the revs get up there.

[07GTS]

Now that's a good idea. Mine knocks it up about 2 psi then falls away a little as the revs get up there.

yea mine does a bit as ill find out soon, it didnt like running both pumps all the time when fuel gets low heated up too much, so ive drilled out the return line more in the assembly as it shrunk to 8mm so took it out to 10mm to suit bout limit closest to AN-8 and im now going to stage the pumps so see how that goes soon as i can get it out for drive

[blindsquirrel]

'Returnless', rail pressure fixed (assumes 58 PSIG), while manifold pressure is constantly variable - ECM must calculate the delta to know which column it's in
screenshot.13-02-2024 08.39.21.png

Same injectors, but referenced to manifold, base pressure 58 PSIG - but when manifold pressure goes up rail pressure does too by the same amount (pressure delta is always the same, even if the ECM is expecting it to change), therefore whatever it calculates the delta to be, all the columns are the same all the way across
screenshot.13-02-2024 08.38.47.png

[GHuggins]

Yep, I was just wondering what the full benefit would be to going through the trouble to get the switches flipped. Was hoping it would better "know" that it was supposed to be changing Otherwise, I'm not seeing the big benefit.

[Cringer]

Found it.

There are 7 switches in total. Default, hot, crank, high flow, cold, low flow, normal. They are defaulted to off. When switched on, the ecm will use the respective fuel pressures in [ECM] 7030 through 7035

How exactly are these switched "on"? The current tune has these fields set...

[ECM] 601 - FPCM Fitted: No

[ECM] 600 - Fuel Pump Type: Fixed

...and that seems like this would qualify for using the values in [ECM] 7030 through 7035 if I understand correctly.


Additionally, the current tune has [ECM] 7030 through 7035 all set to 400 kpa, so I assume that is why the logs all show rock stead 400 kpa of pressure 100% of the time.


If I can get the guy to slap a physical gauge to the rail and get a pressure reading then I should be able to adjust these as needed and then I don't have to mess with the injector characterization on the Fuel tab. I guess the trick will be figuring out how to tune the Low and High Flow modes.

[hjtrbo]

How exactly are these switched "on"? The current tune has these fields set...

[ECM] 601 - FPCM Fitted: No

[ECM] 600 - Fuel Pump Type: Fixed

...and that seems like this would qualify for using the values in [ECM] 7030 through 7035 if I understand correctly.


Additionally, the current tune has [ECM] 7030 through 7035 all set to 400 kpa, so I assume that is why the logs all show rock stead 400 kpa of pressure 100% of the time.


If I can get the guy to slap a physical gauge to the rail and get a pressure reading then I should be able to adjust these as needed and then I don't have to mess with the injector characterization on the Fuel tab. I guess the trick will be figuring out how to tune the Low and High Flow modes.

I'd have to go digging to see what ECM 600 & 601 do. My assumption is setting those as you describe would be the ECM uses the default scalar only.

There is variance tune to tune. For comparison these are in mine


For sure some magic needed for needed for getting it to work. I like the easy to understand manifold referenced fpr and flatline of the inj flowrate table.