Gen3 Coyote Boost a Pump lift pump tuning

[engineermike]

I installed a Boost a Pump on a Gen3 coyote and noticed that the fuel pressure was no longer able to be controlled by the pcm. I spent quite a bit of time experimenting with the different lift pump settings and finally got it working. Note that many have been told by mainstream tuners that tuning isn?t necessary with a Boost a Pump. That?s not totally inaccurate because the Gen3 does measure fuel pressure and modifies pulsewidth to account for pressure higher or lower than desired. However, it still bothered me that the control loop was out of control and excess fuel was being recirculated through the bypass regulator in the tank. The lift pump duty cycle would flatline while not going low enough to get the pressure down.

Voltage vs pressure vs flow - This table had no effect that I could tell. Either this table was left over from the Gen2, which didn?t have pressure feedback PID control, or it?s used as a feed-forward only for transitions. Either way I max?d it out and zero?d it out and still had too much pressure at idle in every test.

Min duty cycle - This was 6.5% stock but the logged duty cycle wouldn?t drop below upper teens iirc. Changing the min didn?t affect the logged data.

FPC slope and offset - This turned out to be the key to making the system work right. Stock values are 2.0 for slope and 0.000 for offset. What wound up working well was 1.8 slope and 0.1 offset. The values work opposite of what you would think. Higher offset lowers the commanded duty cycle min and max. Lower slope increases the max more than it increases the min.

So often people figure things out then keep them close to their chest. I put a lot of time into figuring this out but can?t see how keeping it to myself could benefit anyone, so here it is.

[decipha]

There is also a scalar for voltage commanded when in auto stop. You may need to reduce that too.

[Grim5.0]

thanks for sharing mike!

[DCLTLLC14]

Thank you mike! I never had a customer with a bap and I actually have a gen3 with bap and roush sc that I am doing for a very important guy in the car community this weekend so this should help me tremendously!!

[tording99z28]

What would happen if these variables were not changed when running a BAP? I have a gen 3 being tuned right now and there is some issues with cold start rough starting and running for the first 15-20 secs. After that it smooths out and runs fine from then on. Only does it on a cold start. Mods added were ID1050X injectors, ESS G3 supercharger, and a BAP. Tuner says tune is fine but that the DI is acting funny on cold start. Car was 100% stock before and has always ran fine with no issues on cold start and no codes.

[engineermike]

E85?