Hi, been using the EBL for over 2 years now. I had everything running pretty good until this fall. I changed cap, rotor, ignition coil and the spark plugs. I also went from 0.045 to 0.060 for the plug gaps just to try. From that point on, I've been experiencing weird things. Immediately after that point, I had to re-tune the VE table and even bump the BPC table quite a bit to recenter the VE table. I finally got a good tune and last weekend again, way lean, I re-centered VE table again last night. I bumped the BPC table from 145 to something like 175 (don't have laptop here at the moment). I thought that was kinda weird. Anyway, I checked all the spark plugs and gaped them at 0.045 again. I also found some possible vacuum leaks from intake ports, so I replugged them. I also checked the fuel pressure last night and it's a solid 28lb.

Needless to say, I'm confused. For a 412CI engine, with the big Holley TBI 81# at 26lb, why is everything suddenly changing? My BPC table is way above what the EBL Utility calculates for. What could produce those variations? Nothing of the sort happened last winter.

 

Iam a firm believer to set the BPC table to the calculated value then forget it. If you are using a VAFPR then you could calculate it based on VAC(BPC vs VAC) through use of a Mighty Vac.

BLM will change with environmental temps. It is supposed to. However with IAT input it will respond better. I believe the IAT will change injector pulse width possibly before the NB02 sensor sees a need. Just a better resulting fueling. I see large swings in IAT temps mid summer early morn to late afternoon(70dF to 100+).

I once experience rising learned corrections(BLM) in VE table due to an exhaust leak before the NB02.

edit: I believe Holley rates their injectors at 26 lbs FP(not 12-13 GM).

 

the way I filled the BPC utility is I used a 61# injector and put 26# fuel pressure, that gives me about the 84# overall that Holley calls for. With the other numbers in there I should be using a BPC table of 115. That's how I started when I first setup the EBL, and realized it was way lean and would reach 100% VE everywhere. That's when I started using the BPC trick to center the VE tables. I had been using 135 until last June, then I moved it to 145 this fall, and now am using 174. So my BPC needed to be raised by 40 points so I could use the same VE table. How can that be? I do run an IAT, and the table for IAT vs CTS is all at 100% CTS as I have no idea what to do with that. Also, I have to figure out about the Proportional Gain stuff to get my idle back to normal.

I'm thinking, for the fueling to be that screwed up (leaner) there must be a mechanical problem somewhere. Maybe the IAC is stuck open or something?

 

Use the calculator that RBob enclosed with EBL for BPC vs Vac table (not MAP). I believe it was created off an Aeromotive 13301 he had.

 

If you're talking about the EBL Utility, that's what I was referring to.

 

Check the items you changed right before this issue occurred. With changing the cap & plug the spark plug wires may not be on the correct cylinders. It doesn't take much to throw the tune off.

RBob.

 

I would believe that Utility will calculate differing #'s for each VAC value?

It should show a smaller calculated BPC at 0 VAC(100MAP) and the largest at 90 VAC(10 MAP).