ZL1 fuel pump tuning needs

[jasonz28camaro]

Hi,

I've noticed my low side fuel pressures being in the low 40s at WOT with my setup. I've got mild boltons with e85 on my 68 camaro with a 2018 truck OS. I'm maybe around 450whp ish and I do not feel that I'm running out of fuel, rather I'm not set up correctly in the tune or a mechanical issue with the pump.

I'm looking to see if you guys could point me in the right direction as to what all is needed to change. I've seen some posts about going LT1 car OS to ZL1 pump and it seems to not be that difficult to do but when I compare my truck OS to the car OS there is so much more that's different in the fueling.

I've attached my tune and a log driving around with a WOT pull (wideband not captured in log). Don't mind the timing issue on the WOT pull, I'm trying to sort that out, could be related even...

Timing loss.hpl
2-12-22 update startup modifiers 7500.hpt

[sevinn]

Do you have the fpcm in the car?

[jasonz28camaro]

Do you have the fpcm in the car?

Yes

[sevinn]

Could you do a read with that module as well? There's another max pressure table in there that can set a floor on lo side pressure if it isn't correct.

[jasonz28camaro]

Is there a special way to do it? All I see is the engine and trans when I go to read.

[sevinn]

Is there a special way to do it? All I see is the engine and trans when I go to read.

The fpcm must not be present then.

Try setting ecm 6974 to 500 kpa

[jasonz28camaro]

Physically its present but I guess not able to read with this OS.

I'll up that to 500 kpa and see what it does, give me about an hour.

[sevinn]

Physically its present but I guess not able to read with this OS.

I'll up that to 500 kpa and see what it does, give me about an hour.

If it's hooked up you should be able to see it. Weird that you can't when you go to read.

[jasonz28camaro]

I did not know it was a thing to tune the module itself, I figured there was enough fuel-related stuff on the ECM side of things. I did some searches and came back with certain OS do not allow you to read the FPCM. I'll still look a little more into it and speak to my harness builder if there is a workaround.

[sevinn]

I did not know it was a thing to tune the module itself, I figured there was enough fuel-related stuff on the ECM side of things. I did some searches and came back with certain OS do not allow you to read the FPCM. I'll still look a little more into it and speak to my harness builder if there is a workaround.

What you heard is correct, if the physical fpcm is present though I'd suspect it would be used. c7 vettes for instance don't have an fpcm, the ecm does it all.

[jasonz28camaro]

I did the change you suggested at idle only and it got right around 73psi. I did not do a WOT pull on it though. I put it back to stock and altered table 18102 (min voltage) to reflect a ZL1 and my pressure went to 60psi at WOT. I didn’t get around to adjusting back to 500kpa as I was satisfied with some of the results I got out of upping the voltage.

If your guys recommend adjusting additional tables let me know. Thanks.

[sevinn]

Good deal. Fuel system voltage was going to be my next target so glad you made it there. You hit the big ones otherwise from what I could tell.

[jasonz28camaro]

I do appreciate the help. Thank you.

Now on to my next issue. One of those mysterious timing pulls at WOT in 6 and 7th gear only. It’s in the log above, same tune too. Need to probably start a new thread.

[sevinn]

I didn't look into that yet because you said to ignore it. I will now