On a 7747 ecm how important is the VE table 2??? I know the formula states that for a new VE setting is = to old VE1 +old VE2 x avg BLM / 128 for a specific setting when tuning but I read that table 2 is mainly for a fine tuning of the VE. Now If I'm running a fuel only system can I go ahead and take the values from VE 2 and figure them into VE 1 and null out 2??? Or does the ecm have to see some sort of setting in 2??? Or last would one just leave 2 alone and adjust 1 as needed adding in table 2 of course ?

 

i did just that. i zeroed out all of the table 2 cept the first VE 2 entry which i am guessing is 3600 rpms. i forget? there is a reason not to zero out that one i believe. i later discovered i hit 100 in several spots in VE #1 i changed all to value of 10 in table 2 cept again first entry.

search "zero out" and you will see numerous threads.

7747.

 

That's interesting. My AYDP '6965 cal had that setup from GM.

 

VE #2, is for anything beyond 3600 RPM. VE #1 is not a huge table, so VE#2 is an adder table. For anything about 3600, it takes the top VE#1 table entry, for the KPa you are at, it then adds in the appropriate VE#2 entry on top of it. you can zero out the begining of VE#2, so long as you add the value for each RPM increment, into VE#1. However, you cannot do this in the 3600 RPM cells, as it will use that entry + the VE#2 entry for anything above that range.

 

And the same goes for under 400rpm.

 

good point. add the amount removed from 2 to one but i thought that understood. maybe not. now i remember 400 rpms needs a value in VE2 and i do have one. thanks for bringing that up. i believe it is 10. same as those above it that are represented only in VE1 all 10.


someone once said doing the above affects WOT fueling. i thought it was said it may go way rich as a result. not for me. i am at 13.0/13.3/1 on WB commanded to 12.5/1.

 

You have to use some caution when zeroing out the VE adder table as the ecm interpolates, and the VE may drop at higher RPMs. If there is 0% VE in the 3200 RPM cell and, say, 80% VE in the 3600 RPM cell. It wont go from zero to 80% right away. Instead itll be at some intermediate value when the RPMs are between the two cells. Also, youll want to maintain some VE across the board, or at least in the 3200 RPM cell in the adder table as the engines VE may decrease as the RPMs go up. The last row in the main 3D table is always used, even when above 3200 RPM.

 

Right, because it still needs to scale to manifold pressure.

If it helps, this is my stock VE stuff ($62, '6965, AYDP):





As a side note, I had to take VE out toward the top end (light surging), even with my breathing bolt-ons. And the cold/cool engine AE was also too rich. Ironically, the choke was too lean...