Open Loop/Cold Start fuel

Background: $42, 7747, Auto, 5.7 with a higher than stock psi fuel pump. Regulator is bottomed out and I'm still at I think 16.5psi(haven't checked it recently). Fueling tables are adjusted for this in closed loop.

What I would like to do is lower the fuel being used when in a cold start before getting to closed loop. I realize that when cold, the fuel requirements are going to be higher than closed loop, but I know that it's running richer than needed right now. How can I go about lowering the fuel, and are small changes possible in open loop so as to not go too far and make it run lean?

Yes if you go to lean it will stumble and stall at cold start.

Before you make those changes, have you calculated a new BPW for new fuel pressure?

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Originally Posted by EagleMark

Before you make those changes, have you calculated a new BPW for new fuel pressure?

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Yes, the bpw has been adjusted.

Stock is 134. Should really have accurate fuel pressure and calculate this before any changes.

According to the spreadsheet I've had that I am pretty sure I got here, I need 119, which is where I have had it set for a while now.

Well you've done your homework! :thumbsup:

Here's some notes I keep in my $42 XDF mostly from papers written on DIY-EFI by Rbob years ago.

BPW is the start of everything. Then VE tables when warm or Closed Loop, so everything is an adjustment off VE, if VE isn't right then nothing else will be.

Or when Cold or Open Loop fueling starts here after BPW.
"Open Loop - AFR vs Temp"
This table details corrections to the A/F ratio, based on engine temperature. It includes startup enrichment (choke).
Also "Choke - Cold AFR vs. VAC kPa" effects commanded AFR while in Open Loop.

The current commanded AFR is used in the BPW calculation. This is true of both open and closed loop operation. While in open loop the ECM generates the commanded AFR from two tables: AFR vs manifold vacuum and AFR vs coolant temperature. While in closed loop the ECM uses the stoich AFR term.
This cold engine AFR vs. coolant temperature table is used to control engine AFR after crank and prior to the ECM going into “closed loop” operation.