Disabling EVAP purge during boost?

[NotSure]

I noticed on my logs that I am getting 100% purge duty cycle under WOT, whoops. I did not have any other evap data logged, so don't know if I was pressurizing the system or not. I o have a chart titled LTFT Purge Cells / Reduction Factor (ECM 12510), which goes to zero at the top of the chart of 1016 lb/min. I looked at a 2012 stock CTS-V file from the repository and it only goes to 0.27 at 1016 lb/min. I am definitely into boost at this rate, yet evap purge is still at 100%? Going by this chart, it should not be. I could maybe understand having the purge on with a N/A engine, but the CTS-V has purge at this airflow. My vehicle is a stock 6.2L Gen4 E38 truck with Whipple.

Am I missing another chart(s)? There are also charts for purge duty cycle at Low, Mid, High Flow (ECM 25012, 25013, 25014), yet each of those only goes to "162" in airflow. If that is lb/min it is very little. And both my stock cal as well as the CTS-V cal show a linear increase in duty cycle in the Low Flow, from 0 to 90-some %, and the Mid and High flow charts are 100% across the board.

These charts are all under Fuel/Oxygen Sensors.

[Jeff7577]

I don't know what you have but OEM purge valves have check valves built into them for boosted applications.

[NotSure]

Good to know, and it appears that my stock purge valve, 12597567, is also used on the 2.0L supercharged Cobalt. Looks like it is used on most all Gen4 trucks and on the LS3 and LS7 corvettes as well, for those of you adding boost. It appears the cts-v and the LS9 use a different style that bolts right to the intake instead of sitting off to the side with hoses going to both ends, and so different part numbers.

I still would like to just shut it off at higher loads instead of relying on a check valve, but I guess I am just being OCD.

[Jeff7577]

That unit does not have any check valve, so either GM doesn't think manifold pressure will get beyond it, they can shut it off completely on that calibration, or there is a check valve somewhere else.

Here is an example of what im talking about, with the check valve in the line. 55573017

[wildfan1976]

Remember where the purge valve is located, after the throttle body and before the supercharger so your not pressurized its still at vacuum even under boost.