[Joshinator99]

Originally Posted by travislambert

Thanks for this feedback. It's very good information.

If your pressure is dropping that much, then you are right at the edge of losing all pressure. Pumps certainly flow better at lower pressures, but I don't know that commanding 275 kpa is a good idea. Commanding higher pressure won't help either. I've spent hours on the dyno tweaking fuel pump related settings and it basically was just a long exercise to learn the settings are optimal in stock form (at least for the stock pump).


I assume you are using the Fuel System Voltage Min table. Are you sure that's doing what you think it's doing? I'm not sure it actually increases the voltage to the pump (maybe it does). What it might do though is work against you and cause the FPCM to command a lower duty cycle. If it thinks your pump is working at 15.9 and you still have Base duty cycle table and the VBAT Mult table configured for the stock pump, I bet it will reduce pump performance instead of increase it.

I'd leave the voltages in the tune stock and work to get the calibration for the pump correct if you haven't already (Min DC, Base, VBAT Mult).

In the end, you still may need a voltage booster, but at least the configuration will be correct which will allow the car to maintain steady pressure instead of bouncing high and low.


(BTW. Take this for what it's worth. I'm not an expert and don't claim to be. I've just spent a lot of time experimenting with fuel pump settings.)

Good stuff Travis. I’ve modified the VBat table since I noticed it reduces the duty cycle at “normal” car voltages, so I put that table to 1.00 to stop that. I also put allowed max DC to 130, expecting that to help but it didn’t. Seemed to get worse actually.

Agreed, I’m not sure about the Fuel System Min Voltage table. I just took the stock ZL1 table and tweaked it up a tick to 15.9, but I’m not entirely sure if that helps either. But I feel like the pump is capable of more, but not sure where I’m going wrong.

I guess another possibility is the factory fuel line might not be big enough? I’m running the LPE check and eliminated the tiny OEM one that was pinched into the original fuel hose, so hopefully that is one bottleneck gone. But I found it interesting that I was holding full 2900# rail pressure even though the low side was dropping pretty good, so I’m thinking maybe the check setup helped with that.