Injector offset vs MAP vs VAC tables

[Speedytec]

I'm trying to understand more about the logic behind the Injector offset tables. (I used the Omega spreadsheet data for my 60lb's)
Modified the values for a return style system on my LSJ, but I cannot see the logic or math between the MAP and the VAC offset table. I understand this tables describes the injector latency at a certain pressure differential and voltage, but why are the offset values for a certain MAP and VAC value not the same??
(I do assume that the 99 MAP collumn there should be roughly the same pressure differential as the -1 VAC collumn...)

Why are those offsets described in 2 table formats and can you choose between MAP or VAC, if they describe the same just in a different way?
(looked to a few GM base tunes but those offset tables don't make sense either.)

Just looking for the logic behind instead of just copying the values...

[Speedytec]

Bump.

32 reads... Nobody??

[laser_racer]

I read but can't be any help omega and 04redline were the two to talk to you might try posting this in a more general section of this forum seeing a lot of others don't come here.

[Speedytec]

Yeah, I'm digging a lot in this forum for detailed info, but the injector offset tables are a bit of a black art.
Most interesting was this post of SJSchafer: http://www.hptuners.com/forum/showth...highlight=60lb

He actually studied injector offsets and the effects on his AFR's. And curiously in his 60lb tune there the V vs.MAP table is the exact opposite of his V vs. VAC table, just as you would expect...

(It still boggles me why we can choose for the LSJ's between a MAP referenced offset table and a VAC referenced table.)

[marksrig]

I'm just adding this to this old thread in case someone else is curious. Info here is from Nic (R&D) at Fuel Injector Clinic when I asked which to select when running a return system 1:1 boost referenced. Vacuum was the correct setting for mine.

"That offset select switch changes the table reference for injector offset. You'll notice that you have Offset vs Volt vs MAP, and Offset vs Press. vs IGNV. If you select MAP , it references the first table, if you select Vacuum, it references the second table. You have this setup correctly so nothing to worry about there."