Fuel Trim Cells and Evap?

[HawkZ28]

With my current tune, my Fuel Trim Cell is always at 26, 30, 37 or 38- stock tune they were 3,4,5 etc...

Out of curiosity yesterday, I looked them up in the Help file, and found that my Evap is always closed in these FTC's. What could be the negative- if any- of the Evap never opening?

[highpsi]

I wouldn't think there would be any loss by disabling evap, (other than more hydrocarbons in the atmosphere) but there are many other things that pollute worse! Its main purpose is to burn fuel tank vapors instead of letting them out in the atmosphere... I dont run evap either... Just my 2 cents

[HawkZ28]

I double checked today against my stock tune, and found I was misreading the color red- it's open- not closed- all the time. When closed, it (the status bits) goes colorless. Same as the stock tune. It doesn't seem to close unless the engine is shut off.

My fuel trim cells were still low single digits, which I thought was odd considering it's supposed to be closed in the fuel trim cells that I'm running in with my current tune (26, 37,38).

This is from the help file:

Fuel Trims LS2/LS7/L76, Cobalt SS 2.0L s/c and other later model vehicles
The LS2/7 and others have more cells but follow a similar pattern to the LS1:

EVAP Open
0 - 15 defined by the LTFT RPM and MAP boundaries
16 - Idle PN (AC on)
17 - Idle PN (AC off)
18 - Idle InGear (AC on)
19 - Idle InGear (AC off)
20 - Decel

EVAP Closed
21 - 36 defined by the LTFT RPM and MAP boundaries
37 - Idle
38 - Decel