Howdy!

Trying to add a little more fuel when at part throtttle -- 1500-2000 rpm -- and it just won't do it! Running my stock 7747 ECU, upgraded heads and intake to vortec. No matter how much I tweak the VE tables, I can't the ^#@W&! thing under 15.0-1 at part throttle (testing with my wideband o2). I even upped the injector constant and it's still lean, and rich as heck at idle and WOT. Could it be going into closed loop and ignoring the changes I'm making?

 

I would think so. It's obviously going to be shooting for 14.7:1 in closed loop- pretty close to the 15:1 reading on your wideband (which I assume is mounted somewhere separate from the factory narrow band O2).

Now in the title you said it's running lean WHEN COASTING. Coasting (spinning down with the throttle closed) is a different environment completely. I don't know the tuning tables on these motors very well but factory EFI system tuning almost shuts the injectors off during an over-run or coast-down situation.

 

Yeah, when coasting the injectors are mostly shut off for fuel economy reasons. The locked up torque converter allows this.

 

Ah yes - I should clarify, this behavior is happening when maintaining a constant speed, so the throttle is not completely closed. I suppose I'll try disabling closed loop then and go back to my old VE table (before I put all kinds of ridiculous values in there trying to add more fuel Do most folks here tune with closed loop disabled?

 

What is the BLM and INT doing during this condition? IOW is the INT moving causing the BLM to move?

I presume 7747 does not have HWAY mode enabled? I cruise at 72 with it enabled and I see 15.7/1

 

Haven't logged the BLMs lately -- I'll fish out my cable and do some data logging. I'm pretty sure highway mode is enabled, but my measurements were at around 30mph so I don't think it's kicking in yet...maybe I'll disable that just to be sure.

What I don't understand is if in closed-loop, the computer is constantly making adjustments trying to hit 14.7-1, how is any tweaking to the VE tables going to affect the fuel mixture? Isn't the computer just going to override any changes I make unless it's in open-loop?

 

Yes constantly unless in AE or PE or coolant temps <155F.

Correcting VE is a good idea since it allows ECU to work faster in arriving at stoich AND if out of boundaries it cannot make proper corrections. with cooler weather past week I see BLMs rising. Normal. I saw Learn pull(-) 3% of VE across the board.

when in OL the VE table is used so needs to be reasonably close.

 

Doesn't the TCC disengage when you pull your foot off the pedal?

 

The tcc disengages when you step on the brakes.